It's kind of a nice idea and a decent start. It doesn't seem to do depth of field very well (f8 should make the background pretty sharp at 43mm; f2.8 at 200mm should have a completely blurred background).
It would be nice if it showed non-Canon terminology (Canons say "Tv" while almost all other cameras say "S", for example), at least as an alternative. It should also visually indicate the value being automatically chosen in the different modes.
No P (program) mode. This is actually the most useful shooting mode on many DSLRs, especially for novices. It lets you trade off aperture vs. shutter speed.
__Advanced Nitpicking__
No auto ISO mode. (Great feature of Pentax cameras -- it's like M but the camera picks the ISO that will work.)
No ISO-priority mode.
It doesn't allow for things like camera shake and the child's motion (you might pick 1/60 of a second to capture the child sharply, while needing 1/250, say, for the pinwheel).
It's not worth allowing ridiculously high (small) apertures (e.g. f29) -- if you're not going to do diffraction, so I'd stop at f22. It would be nice to have faster (bigger) apertures than f2.8 to really show the benefits.
It shows autofocus points, but they don't do anything. It would be interesting to allow the user to pick a focus point and assume the metering is weighted on that position, but that's getting pretty advanced.
Some good thoughts here, but I think you're missing the big picture. This appears to me to be a great tool to learn how exposure works. Using aperture or shutter priority sorta defeats the purpose of that.
> No P (program) mode. This is actually the most useful shooting mode on many DSLRs, especially for novices. It lets you trade off aperture vs. shutter speed.
oh boy. that's actually the mode that keep novices clueless about what's going on with the settings.
> No auto ISO mode, No ISO-priority mode, etc. etc.
well, ISO + TIME + APERTURE are ingredients of EXPOSURE, and that should be all you need to know to start shooting. you know this and you can grab the newest high-end dslr or your grandpa's 35mm oldie and know what you're doing. the rest is just geekery.
> oh boy. that's actually the mode that keep novices clueless about what's going on with the settings.
That's hardly the fault of the mode itself — it's just a large number of SLR-buying consumers probably didn't need the complexity (or heft) of an SLR, but have the misconception that an SLR will outperform a compact or bridge camera 100% of the time. And so they buy one.
The issue there is that a lot of these people are coming from mid-range compacts a couple of years old, and see the SLR as the next logical step. A high-end compact (S95, LX5, XZ-1) or a good bridge/micro four-thirds camera (GF1/2, E-PL2, GH2) would be a far more practical solution, and nigh-indistiguishable until ISO1600 anyway.
As a side-note, I went from shooting portraits w/ a 5D2 + primes to a GF1 + 20mm f1.7, since I no longer had the time to keep the portrait gig up as a consultant. My GF1 is no full-frame SLR, but it's very close to the entry-level SLR's and in a much smaller package (with better glass to boot).
> oh boy. that's actually the mode that keep novices clueless about what's going on with the settings.
Of course. Criticizing it for not having Program mode stuck me as similar to saying "Nice sportscar, if only it had Automatic transmission". People buy high end DSLRs and don't take the time to learn what the various A-S-M-P modes do. It is the fault of the mode and the manufacturers who put P or Green modes on the SLRs, and recommend them as idiot proof modes.
I know how to use my SLR, I regularly use it in full manual tuning every last exposure variable in manual focus, sometimes with multiple manual flashes too.
Yet, I still try to remember to leave the camera in P when I put it away and often shoot in P. It's a relatively idiot proof mode; it's unlikely that, if I just pick up the camera and shoot because I'm in a hurry for whatever's in front of me, P will give me a ridiculous, unusable exposure.
The chances that you want to deliberately underexpose or overexpose your photo are lower than the chances that you want to specifically control aperture (for DoF) or shutter speed (depending on how you want to capture motion in your scene). It makes lots of sense to automatically set the ISO while you control the other parameters (while being aware of the quality loss inherent in high ISO, and keeping track of it).
>well, ISO + TIME + APERTURE are ingredients of EXPOSURE, and that should be all you need to know to start shooting. you know this and you can grab the newest high-end dslr or your grandpa's 35mm oldie and know what you're doing. the rest is just geekery.
Perhaps I misunderstood your point but that doesn't sound right. Iso does not control exposure: in case of film it is the sensitivity of a particular stock, and in case of sensors it's basically analog gain. Since to use a different ISO in a film camera you'd need to use a different roll or sheet of film, you can't vary ISO on a "grandpa's camera" very easily unlike with a digital camera.
You missed the point, which is that you learn how to use the 3 exposure controls: shutter speed, aperture, iso; and then it doesn't matter if you can change iso on the fly on digital or by changing a roll of film - you know how to take pictures and that's it. We're talking education.
The worst a newbie can do is to focus on learning 'camera modes' instead of learning how photography works - that's why all those "P", auto-iso, etc would be pointless when you want to learn (and that's what this simulator is for).
You don't actually understand program mode on a DSLR. It's actually like not having to switch from A to S rather than the old "I don't care what my camera does as long as my photo comes out" mode you get on point-and-shoots.
> well, ISO + TIME + APERTURE are ingredients of EXPOSURE, and that should be all you need to know to start shooting
So depth of field and the way metering actually works aren't important?
> > well, ISO + TIME + APERTURE are ingredients of EXPOSURE, and that should be all you need to know to start shooting
> So depth of field and the way metering actually works aren't important?
Well, we can say "everything is important" and there's no sense to number this stuff to infinity. But if you insist: metering is also just a tool, which you can live without (using exposure value tables), knowing how exposure works is the core of photography.
AF in major brand name, probably. I just got a 2.8 135 for $20 on eBay and with people probably having something short of a full frame sensor, that's a pretty cheap 2.8 with "200mm" framing.
Not saying it's a comparable lens, just saying that the simulator isn't necessarily talking about a cost prohibitive situation.
Given this is intended to teach exposure/DoF, it'd be nice to be able to bypass the "SLR" aspect of the camera, ie provide a "continuous snapping" mode where moving a slider instantly updates the "photo" instead of showing the fake autofocus sensor overlay.
It's definitely a neat way to interact with it in a browser, though. If you're looking to learn these relationships in a less interactive way, I thoroughly recommend the book "Understanding Exposure" by Brian Peterson.
You can go up to ISO 1600 and get (more or less) unnoticeable noise.
Note that you have to switch to RAW to show sensor noise-- JPEG mode will blur away noise, trading fine detail for smooth images.
Also that lens is really amazingly sharp at both ends of its aperture range. In the real world you wouldn't get anywhere near that level of performance without spending tens on thousands of dollars on a prime (non-zoom) lens.
It's exaggerated, to be sure, but it's an instructive exaggeration. Showing the noise visible in a 4k still at 8% enlargement isn't going to help a novice understand ISO tradeoffs.
It's a learning tool, and so I would like it to teach that almost all lenses made of mortal glass are less sharp at either end of their aperture range; and that taking a picture of a landscape on a sunny day at f2.8 is a bad idea.
If you have ipod/iphone/ipad, have a look at <http://www.islap101.com/>; (and review of it at <http://lifehacker.com/5501364/photo-tutor-teaches-basic-came....
There are actually two apps (one for shutter speed and one for aperture) - and they teach/display those concepts really well - even if I say so myself :-). There are also "recipes" for taking photos in various environments/situations - all prepared by professional photographers.
A difficult one from implementation standpoint: When I change the distance, it just scales the girl's face as a 2D image -- no perspective. :-) I'm not being picky, just that this is sometimes a consideration for me when clicking...
Wish someone can point me to the mathematics behind this stuff. I figure ISO means gain of some amplifier inside so less photons would be needed to get to the same voltage at the expense of more noise. I can see how with the two auto modes, aperture size and shutter speeds relate to each other (basically you need to gather a similar number of photons, given the ISO setting). Yet do not know the mathematics behind why aperture size affects the depth of focus. Likewise, why focal length does the same. What's the mathematical definition of Fstop. And last but not the least, what role the sensor size play into all of this.
Still do not know how sensor size affects things. Will read more, and hopefully will be able to construct a single mathematical model that couples all of these together.
Can anyone explain why the "ISO" setting exists on digital SLR cameras? It seems like this is an unnecessary holdover from film cameras.
I ask this as an owner of a Canon Digital Rebel that knows very little about photography. What does changing the ISO setting get you that changing the exposure time or aperture wouldn't?
ISO is sensor sensitivity. Higher settings multiply the numbers that come from individual sensor elements by increasingly large amounts.
Image sensors are not perfectly noiseless, of course, and the higher the ISO is, the noisier the image, which appears as random speckles of colored dots.
You don't notice the difference, though, because you're probably shooting in JPEG mode, not in RAW. In JPEG, the Rebel tries very hard to cover up its sins, and will blur away sensor noise, which is hard to notice unless you grovel over areas of fine detail at 400% magnification.
Useless editorializing: A SLR isn't a great purchase for someone who knows very little about photography. A point-and-shoot is lighter, cheaper, more durable, easier to use, and in the vast majority of situations, will produce identical results to a SLR. You then graduate to a real camera when get fed up with the various fiddly technical limitations of a point-and-shoot; and bonus, you still have the small camera, which is the one you take with you when climbing mountains, or on vacation, rather than lugging around five kilograms of japanese glass.
Tedious polemic: I dearly hope you have more than one lens. The enormous price premium of a SLR is mostly for the privilege of being able to change lenses. If you just stick with the kit lens, then you will have spent rather a lot of money to accomplish nothing a point-and-shoot couldn't do.
Just as a counterpoint (not to pick a fight), I'd disagree with a lot of what you said in the latter portion of your post.
Entry level SLRs are great, even for people who don't know anything more than point-and-shoot. The advantage of an SLR is that it will focus faster, meter faster, and ultimately take the photo faster. This is a huge advantage for parents, whose children are fast moving targets.
What's not necessarily a good idea, is buying the biggest, most expensive SLR you can find. Canon and Nikon both make entry-level SLRs that have modes specifically targeted at novice photographers who will never leave full-auto mode. Buying a more expensive model primarily gets you features. Features that you won't use. The hardware is remarkably similar until you get up in to cameras that cost thousands of dollars.
Many people believe that the huge lens is what makes SLR photos clearer in more conditions, but that's not the whole story. The lens is large because of an aspect of the SLR that you'll probably never see: the sensor. The single greatest reason for the increased image quality of an SLR is sensor size. When you shoot with a compact point-and-shoot, you're capturing light with a sensor the size of your pinky fingernail. You could shoehorn the fastest, largest, most expensive SLR lens on to a compact point-and-shoot, and the photos it takes wouldn't compare to an SLR with even a modest lens. The sensor in an SLR camera is closer to the size of a postage stamp, and this makes all the difference.
Keep in mind that compacts these days shoot comparable resolution (megapixels) to SLRs. This means that each "pixel" in a compact is microscopically small when compared to the "pixels" in a SLR sensor. This means less area for light to fall, and less light collected.
So, even with one lens, and in the hands of a novice, a reasonably priced SLR can result in sharper, more well timed photos in a more diverse range of conditions.
Also not to pick a fight, especially since your post has a lot of merit if this were 2009, but point and shoots and bridge cameras have come a long way. You can essentially get all the benefits of an SLR in the higher end point and shoots for several hundred dollars less than even entry level SLR kits. There are a number of point and shoots with the same size sensors as entry level DSLRs, same instant on, equivalent lack of shutter lag, equivalent metering, etc. etc.
For most people, the upsell to the DSLR probably isn't worth it at this point.
There's a tradeoff between the physical size of your lens, the physical size of your sensor, and your maximum optical zoom. The way you put it, you make it sound like you can have it all in a compact, but that's just not the case. A bridge camera with a substantial zoom and large sensor size will be as about as big as a DSLR with a lens of similar capability. A compact point and shoot will either have a smaller sensor or a less capable optical zoom, and probably both. I have a fairly high end compact, albeit one from late 2009 (Canon S90), and it is nowhere near as capable as an entry-level DSLR in terms of focus speed, continuous shot rate, instant on etc.; and the S95 from late 2010 isn't much more capable (720 HD video, stereo mics and firmware update).
Well of course not. You also don't get interchangeable lenses. I never said you could get it all in a compact.
My point was, for most people (particularly those who this neat little program was made for), the quality in the high end point and shoots is there. The G12 I used late last year performed very well in all of the categories you mentioned. And for nearly half the price of a basic dslr kit, by the time you're all done with it.
http://www.imaging-resource.com/PRODS/G12/G12A6.HTM indicates that G12 power on to first shot is in the region of 2.7 seconds. I can turn on my D90 and take a shot in a single continuous move of picking it up and aiming it - http://reviews.cnet.com/digital-cameras/nikon-d90-with-18/45... says it's 0.2 seconds, though with AF added in, I'd say it feels more like 0.9. Somewhere between 15x and 3x faster makes a huge difference in reacting quickly in e.g. a party, or sport. The D90 gets over 4 shots per second continuously, but it seems that the G12 has a hard time getting 2. The sensor is also pretty small (AFAIK it's the same as the one in G11 and S90); that lets it get higher zoom levels at the cost of quality in low light. All that in a pretty bulky package (IMO - it's bigger than the S90, nearly twice the weight, and the S90 isn't exactly small).
What I'm getting at here is that if you're walking about on holiday in a city, something like the S90, or maybe the G11, would make sense (though I think the G11 might be a little too big for comfort, the S90 is already quite a bit). If you're specifically trying to take photos, rather than just bringing a camera along, then you have a lot more freedom with a DSLR.
My point is that, for people who don't know how aperture, ss, and iso affect exposure, the 2.5 second difference in startup time and the 2 fps difference in burst probably isn't going to make a big difference in their user experience.
Of course you're going to have more freedom with a DSLR. That's the whole point. But, if you can't figure out what the aperture dial does, the freedom is probably going to be lost on you, along with the extra $400 you're going to spend.
I'm not anti-DSLR or anything. I've probably bought and sold $50k worth of gear in the last 5 years. DSLRs are awesome and they keep getting better. But, compact cameras have gotten pretty damn good in the last couple of years. For many people, and many different applications, they will fit the bill. If you're a sports shooter, they certainly won't.
I feel like you're getting piled on, sorry. Although I guess someone would have come along and made the point.
I don't disagree with you entirely. There are APS-C compacts available that have many of the advantages of a DSLR, but I can't see where buying something like a G12 for $500 makes sense when a Nikon D3000 is available at the same price point.
My opinion is that if you need a compact, get a compact. Pick up a Canon SD1300 for $150 and go crazy. I did a (personal, not school) photography project with my SD870IS and took some of the best photographs of my life.
However, I feel that parents, especially, can benefit from a DSLR, specifically because of the speed. My mother bought a Nikon DSLR a couple years ago at my recommendation because she complained of "always missing the shot she wanted" with her Canon compact. She's been thrilled with her DSLR because she can pick it up, flip it on, and start shooting. There's no waiting for a screen to come on, she simply flips the switch that is right under her index finger, looks through the viewfinder, and pulls the trigger. When your 4 year old grandson is doing something adorable in the living room, the difference between compact speed and DSLR speed does make a difference.
I see your point completely. I will say that the best camera is the one you have with you. The reason to buy a G12 over a d3000 is because you can literally fit the G12 in a pocket (although not the most comfortable solution) or in even a small purse. You can't with a d3000. It's something you have to always consider "Do I want to take this with me?"
I was not clear above in the discussion of image quality (got sidetracked with more or less irrelevant arguments about sensor size/dynamic range/etc.). I was attempting to say that image quality as a whole from the higher end point and shoots is on par with DSLRs for almost everyone. See here for a comparison with the 2 generation old G10 v. a $40k medium format rig: http://www.luminous-landscape.com/reviews/kidding.shtml
I take up photography in stints of a few weeks to a few months. I get inspired to do some photography, take some photos, then leave it for other pursuits. The last time I took it up, my gut reaction was that I needed to replace my old Canon A1 with a modern DSLR. Prices had come down significantly, and I couldn't possibly do good work with my compact, right?
Well, rather than rushing out and buying a DSLR, I decided to go shoot with my compact SD870IS. I'm so glad I did. It gave me a chance to re-focus on the basics without worrying about what settings I was using. I left the camera in full auto and focused instead on LOOKING at what I was about to shoot. I was really pleased with the result, and I'm 100% convinced that it improved my photography as a result.
Some examples of the photos I shot with the SD870IS:
I could not have taken the shot of the grasshopper with a DSLR because A) I wouldn't have been able to grab the camera, mount a macro lens, and get ready to shoot in time, and B) the DSLR wouldn't have fit in the space I had to put the camera to get that shot.
Then again, I couldn't have taken these shots with the compact because I couldn't quickly change settings for good DOF (first photo) and I'd have missed the moment because of speed (arguably for both).
I just checked BHphoto and the G12 costs more than an entry level Canon,Nikon or Sony dslr with a kit lens. So while the G12 is a great camera (I have a G10) and there are many good reasons to buy on, price isn't one of them
Yes, they're about the same price. Once you kit out the DSLR with a lens that covers a comparable range as the pocket cam, you're at a couple hundred more. Plus you've got to carry two (possibly three) lenses around.
imho the 2 biggest differences between a DSLR and a compact is the focus speed and the dynamic range. DLSRs have larger sensors, so by laws of physics, they gather more light and will always have more dynamic range than compacts or smartphones
I can think of four off the top of my head. Sigma DP1, sigma DP2, Leica X1, and the Fuji X100. The first two will cost you as much as an entry level DSLR, the latter two a lot more. Non of them can be considered a reasonable equivalent or replacement for an entry level dslr. What cameras where you thinking about?
We bought the camera in 2005. The quality of entry-level digital cameras was horrendous at that time. The primary concern was that it would take pictures without lag, so you're exactly right.
When a photon hits a pixel it produces an electrical signal. You can think of the ISO as the amount that signal is amplified. So, if you want to keep aperture and shutter speed at certain levels, you can adjust the ISO to produce a usable image. The tradeoff is that when you amplify a signal a great deal, it gets noisy.
Changing the ISO at time of exposure actually increase the amplification at the sensor level. Changing the exposure in post processing just shifts bits around (the advantage of RAW is that, depending on the camera, it captures between 12-16 bits vs. 8bits for jpeg images and it's not compressed so shifting the bits around doesn't have quite as noticeable an effect).
ISO is a trade-off between noise and speed. Sometimes you need the speed, like at a nighttime party or sports, and sometimes you need the perfect details, like shooting landscapes.
In general, you want to shoot at the lowest ISO which works in any given situation.
A longer exposure can result in object or camera shake blur. Wider aperture reduces depth of field, making it harder to focus.
Sometimes, you'll need all three to get enough light in the shot: A hot sensor, a longish exposure, and a wide aperture.
The beauty of digital photography is that you can take pictures all day at no cost and see your results instantly. So instead of running this program, get your friend with an SLR to go on an outing with you and let you do most of the shooting.
Go outside and fill up a memory card while you systematically work through the settings. After you get the hang of exposure you can start in on the different settings for metering, autofocus, manual focus, jpeg processing, black and white, motor drive, use of flash, different lenses, not to mention composition choices, interacting with the subject, use of filters, creative panning or rotating. Real photography is more fun than tweaking sliders on a flash app.
add.: it gives a good foundation regarding teaching exposure itself, but, apart from not explaining (nor visualizing) that focal length and perspective are two separate attributes of optics, it also misrepresents the meaning and function of the ƒ value in a very common way often repeated even by seasoned photographers, in that it suggests (and indirectly claims) that ƒ only has to do with the aperture of the lens, and that ƒ is an indicator of what depth of field you will have. In reality, ƒ only tells you how much light is passed to the film plane; it does not tell you the state of the lens' aperture, nor does it say anything about the depth of field. This misleading explanation regarding ƒ is widespread even in literature.
Actually this is not quite correct. F is ratio of aperture to focal length. As such, it does not tell you the absolute values of either, but it definitely does relate to DOF (although this will be affected by the focal length value - e.g., for the same F, you could have DOF of a few mm at short focal length, and a few dozen metres with long zoom lenses).
It's entirely correct. ƒ relates to DoF only in that it's relative to the maximum aperture of a specific lens. Without knowing the specifics of the lens, you cannot know from arbitrary ƒ value if the aperture has been contracted (narrowing the flow of light, thus increasing the DoF), if it's just really dark glass in the lens, if someone has a TC mounted that steals 1-2 exposure stops, or if someone has simply used a gray filter or two attached to the end of the lens. I can produce two identical exposures, both of ƒ/8.0, where one has a narrow DoF and the other 4 aperture steps deeper DoF, by simply using a gray filter in one shot, and contracting the aperture in the other. In a third example I can use a very, very dark lens such as f.e. what Leica used to produce in the 60s, still exposing at ƒ/8.0 in wide-open aperture, reaching the same exposure and achieving a narrow DoF (contrary to what anyone would think just knowing it's ƒ/8.0), but without having stopped down a single step and without having used gray filters.
ƒ relates to DoF only in that it's relative to the maximum aperture of a specific lens.
No, the f/ratio is f/D, which determines the divergence angle of the ray bundles that end up on the detector plane, and this is what determines the depth of field. You can not produce two exposures that have the same focal length and f/ratio that have different depths of field. Adding an ND filter will just make one image darker, it will not change the depth of field. You can't change the aperture without changing the f/value, because the f/value determines the aperture.
You can not produce two exposures that have the same focal length and f/ratio that have different depths of field
Just to nitpick, you can if you change the size of the film/sensor. f2 on a medium format camera looks very different than f2 on a digital P&S sensor. But other than that you are correct.
"You can not produce two exposures that have the same focal length and f/ratio that have different depths of field."
I am not sure why we are both establishing to one another that DoF is determined by the dispersion of the light hitting the film plane when we already know this. My Mamiya Sekor 50mm ƒ/6.3 has a DoF not even tangibly different from my Nikkor 50mm ƒ/1.4, unless I stop the latter down to ƒ/6.3 which produces two identical exposures at same ƒ/ratio but with very different DoF.
You aren't suggesting that your Sekor 50mm at F/6.3 has a DOF simliar to your Nikkor 50mm at F/1.4 for a subject at similar distances? A 50mm @ F/1.4 is a tight portrait lens, that frequently trips me up and ends up with a lot of unfocussed pictures (well, focussed on the Tip of a nose, or an ear-hair) - whereas a 50mm @ F/6.3 is in an entirely different story. I don't recall having too many out-of-focus pictures at F/6.3 on any of my 50mm lenses.
Can you, perhaps, explains where you are getting your definition of "F-Stop?" Charitably, I'd like to believe you are just using a little known definition of the word, and I'd love to see your source material. I'm sure it will open my eyes to a different perspective on photography than what I've been operating with the last fifteen years.
No; the larger sensor size of the Mamiya as a medium format camera will give less depth of field for a given aperture than the 35mm Nikon.
Otherwise you're right, so in the odd circumstance the poster has a Nikkor 50/1.4 medium format or Mamiya small format 50/6.3 then their depth of field characteristics will be as you said. I'm also pretty sure that even on 6x7 50mm @ f/6.3 wouldn't give DoF characteristics anywhere near 50mm @ f/1.4 on a DX sensor (as the extreme examples to artificially push them closer together), and they'd have a radically different field of view.
I agree with the parent. F-Stop is the ratio of the Focal length to aperture diameter. Increasing that ratio, increase the depth of field. Decreasing that ratio, decrease the depth of field.
Instinctively, F23 will put everything in focus (which is why we use it to identify dust spots on our CCDs, whereas F1.4 on anything reasonably close is going to have a DOF measured in inches.
Can you come up with a counter example where DOF doesn't change in this direction?
Apologies if I'm missing your entire point - I've been starting at it for five minutes, not sure if you are going a different direction.
"Can you come up with a counter example where DOF doesn't change in this direction?"
I gave three examples above. I can elaborate: DoF changes depending on how you strangle the light by contracting the diaphragm the lights passes through (thus preventing light from dispersing), not from having a higher ƒ value. A really dark lens is a good example of this. Some can have a light throughput that begins at ƒ/6.3, or even ƒ/8.0, yet at wide-open aperture they produce as narrow DoF as f.e. my Nikkor 50mm ƒ/1.4 does, which is 5 exposure steps brighter - or, as you reason, 5 aperture steps more open. Why? Because their apertures are wide-open in both cases.
Sorry, but you are wrong about this. Look at http://en.wikipedia.org/wiki/F-number
You seem to be thinking of something similar to what the Wikipedia article calls "T-stops", a calibration of the absolute transmission of different lenses. That's something different from the f/ratio.
Are you nitpicking? You can point to aperture stop theory and the history of the f-numbers etc. indefinitely, but ƒ is and will remain synonymous with light transmission (or "T" as you keenly insist; thank you, I am familiar with it) in every single practical situation of photography, no matter how much you try to balance the needle on its tip.
hackermom, I mean this with earnest sincerity - so please take it in that nature; In fifteen years of photography, photography classes, photography magazines, and photography books - I have never, ever, had anyone suggest that ƒ is synonymous with light transmission.
It is possible, that I, and every photographer, photography magazine, photography book, photography instructor, technical reference, manufacturer, and Wiki-Page, has been using the term incorrectly all this time - but could you stop for a second and possibly consider that perhaps you might be the one using it somewhat differently than everyone else?
At the very least - look at a camera, and note that when you set the "F-Stop" to, or read it to be, say, F/3.5, it does precisely the same thing to the camera if you are in a completely pitch-dark room or outside on a very sunny day.
That alone should suggest that F-Stop is not a measure of light, but instead of something else, and, perhaps also consider that it is, as I have suggested numerous times on this thread, the ratio of the focal length to aperture diameter.
You can't adjust your F-Stop with dark lenses. F-Stop is not a measure of light coming in, it's a measure of the focal length to the aperture. Light conditions prior to hitting the aperture (Either by flashes, sunlight, or dark lens) are entirely separate from the concept of F-Stop.
For a given focal length on a subject in focus at a reasonable distance (not at infinity), increasing the F-Stop will always increase the DOF.
Can you explain why the ratio of aperture to focal length would change simply by using dark lenses or grey filters? The implied meaning of "ƒ only tells you how much light is passed to the film plane" is that ƒ would change merely by adding or removing a filter, rather than adjusting aperture or focal length.
ƒ is in every practical use an indicator of how much light comes out of the lens, nothing else. Two lenses of identical diameter and identical focal length can at wide-open aperture have two completely different ƒ values (due to, among other things, the brightness of the glass used in the groups of lenses inside), yet produce identical DoF. This is why ƒ tells you not the state of the aperture, which is primarily what affects your DoF, but rather how much light reaches the film plane.
F is not an indicator of light coming out of the lens. It is the ratio of the Focal Length to your aperture diameter. Nothing else. It says nothing about the amount of light coming out of your lens. And, indeed, cannot.
Two Lenses of identical diameter [edit: aperture size] and identical focal length, by definition of the concept "F-Stop", will always have the same F Values. Period.
This explanation is going to confuse non-photographers because for modern 35mm format lenses the difference between the maximum f-stop (which is purely the ratio between the focal length and the diameter of the aperture) and the maximum t-stop (the actual amount of light transmitted through a lens) are minimal (no where near full t-stops of light loss). Two lenses with the same focal length at the same f-stop with the same distance to the subject are going to produce the same DoF[1] and same exposure.
[1] To really understand how to calculate DoF for the format you are shooting with and the size you are viewing at, you also need to understand Circles of Confusion (CoC). The same (effective) focal length lens at the same aperture/focal distance and printed at the same size is going to give dramatically different DoF if one camera is 35mm format and the other is large format (8x10).
One thing we should also remember that because of the finite size of either silver halide particles in films or pixels in image sensors, it would not make sense to use very high F values - it would just not serve the purpose since once CoC is comparable with the size of the minimal light-sensitive particle/element, further increase in F will just reduce the amount of light without any increase in sharpness (e.g., a line which has the same width as the light-sensitive element would be recorded in the same way as a line which is only half as wide). For cameras with lenses that have very short focal length (such as, e.g., mobile phone cameras) pretty much everything is in focus (beyond a few dozen cm) even at low F (if you can control it, that is) - just because CoC diameter is so small it is comparable with pixel's dimensions of the image sensor. They are, in effect, "permanent focus" cameras.
Kudos. But if you are a newbie, then perhaps it would be more useful for you, in order to learn how to use an actual DSLR in the field, to reduce the 'Lighting' to more difficult situations ('Overcast', 'Bright Indoors' etc.) and...
1.) set up the simulator to Tv mode and play with the 'Shutter Speed' and ISO primarily
...and after this:
2.) set up the simulator to Av mode and play with the 'Aperture' and ISO primarily.
In this way you will learn how far you can go in real situations and what results you might expect.
HTH
(EDIT: Ok, you can play with the distance & focal length but I think that for the 1st step it is better to concentrate on the points above).
thanks,
so why would Tv mode be more educational than M (which I am guessing stands for Manual) which also allows for playing with shutter speed and ISO ?
Indeed there are cases in which one can use the M (Manual) mode. But usually these cases are rather corner cases, especially for us, the beginners. Basically you ditch the DSLR's photometric engine which does most of the time a very good job, (except some rare situations in which the illumination is very tricky, you want to achieve very special effects etc.).
Besides that, it is enough more difficult to play with four variables (Aperture, ISO, Speed AND the exposure indicator (usually a vertical beam in viewfinder)) compared with two variables (ISO & Aperture or ISO & Time respectively) or with just one (Aperture or Time - if you have the ISO set to Auto).
The main difficulty here isn't that someone (you) can cope (or not) with four variables in a simulator but to adjust them quickly and exactly in the field given the very short amount of time which you (the photographer) have at your disposition to take "the shoot".
That's why the most photojurnalists (from which, more or less, is your truly also) avoid the M mode. OTOH, I have very close "brothers" which are 'studio creatures' which prefer the M mode.
And now to respond directly to your question, having the Tv (or Av mode) will give you a much 'closer to real' simulation (especially if you are on-field, on-street, on-sports etc. photographer) and will allow you to concentrate rather on the effect you want to achieve (for ex. how to simulate a good moving effect of the child's rotating toy) in the smallest amount of time (think that in the real world, the children aren't so frozen like the one in our simulator :-) ) and not to concentrate so much in obtaining a correct exposure. Usually the metering system does the job rather well. These systems have enough advanced features today to help you in avoiding the M mode with its quirks: exposure modes, over/underexposing by 1/2, 1/3 EV etc.
HTH
PS: Disclaimer: No, I'm not against the M mode. But I want to stress its limited usage today. Of course IMHO.
It would be nice if it showed non-Canon terminology (Canons say "Tv" while almost all other cameras say "S", for example), at least as an alternative. It should also visually indicate the value being automatically chosen in the different modes.
No P (program) mode. This is actually the most useful shooting mode on many DSLRs, especially for novices. It lets you trade off aperture vs. shutter speed.
__Advanced Nitpicking__
No auto ISO mode. (Great feature of Pentax cameras -- it's like M but the camera picks the ISO that will work.)
No ISO-priority mode.
It doesn't allow for things like camera shake and the child's motion (you might pick 1/60 of a second to capture the child sharply, while needing 1/250, say, for the pinwheel).
It's not worth allowing ridiculously high (small) apertures (e.g. f29) -- if you're not going to do diffraction, so I'd stop at f22. It would be nice to have faster (bigger) apertures than f2.8 to really show the benefits.
It shows autofocus points, but they don't do anything. It would be interesting to allow the user to pick a focus point and assume the metering is weighted on that position, but that's getting pretty advanced.