[Pål Jensen]

Since you have the equipment at hand, it should be easy for you to take two pictures, one FF, 40mm, f/4, and one APS-C, 24mm, f/2.8, and show how un-equal they are.

Theres no law that says lenses need to have the same DOF wide open in order to be equal (equal lenses give the same angle of view and the same exposure at the same ISO). Even if they do have the same DOF wide open they won't have the same DOF range and hence not equal anyway (in your example the FF lens give less DOF control). This is because the DOF characteristics is a function of the format size and hence DOF and format is totally locked to each other. The DOF caharcteristic is dictated by the format so that equivalent lenses do not display the same DOF at the same numerical aperture.
In addition hardly anyone buy eg fast lenses for an EXACT DOF wide open and wide open only but because they are fast and useful in low light and for freezing action (paper thin DOF is in most cases a problem). In old Pentax lens brochures there was no word about DOF on their fast lenses but about their low light capabilities. Paper thin DOF is red herring as 99,99% (a conservative estimate) of all images do not display DOF thinner than what is available with APS. If DOF was the deal with fast lenses they would not have been called fast but narrow.

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Last edited by Pål Jensen; 06-27-2012 at 03:14 PM.

[ElJamoquio]

1) The last time I was taking portraits I shot at 200mm f/2.8 and would've loved to have a 300mmf/2.8 FF instead, the pictures would've been better. In fact even at 200mm f/2.8 FF some of them would've been better.

I also often shoot pics of hummingbirds for fun, and a lot of the time they have distracting backgrounds. I'd much rather have lower DOF for some of those pics. It wouldn't turn a 3star pic into a 5star, but it could turn it into a 4star.

2) My lenses all go to f/22, at least. I can't recall ever wanting to go past f/22 for 'just' DOF purposes (blurring pictures is another matter of course). I conclude that I will never, or at least, very, very rarely want to have greater DOF than is possible with a FF camera.

3) ISO is misleading when considering sensors of different sizes. It's better to refer to what we're actually talking about, which is (acceptable) noise, or rather, SNR.

[maxfield_photo]

In fact, many LF photographers use that format to get that endless DOF look. The control over DOF is the same for APS and FF but in most cases the APS range is more useful...

I think they use large format so that they can shoot at f/22 without having to worry about diffraction. Or another way to look at it is if they shoot with a 4x5 then a 16x20 is only a 4x enlargement.

[Rondec]

1) The last time I was taking portraits I shot at 200mm f/2.8 and would've loved to have a 300mmf/2.8 FF instead, the pictures would've been better. In fact even at 200mm f/2.8 FF some of them would've been better.

I also often shoot pics of hummingbirds for fun, and a lot of the time they have distracting backgrounds. I'd much rather have lower DOF for some of those pics. It wouldn't turn a 3star pic into a 5star, but it could turn it into a 4star.

2) My lenses all go to f/22, at least. I can't recall ever wanting to go past f/22 for 'just' DOF purposes (blurring pictures is another matter of course). I conclude that I will never, or at least, very, very rarely want to have greater DOF than is possible with a FF camera.

3) ISO is misleading when considering sensors of different sizes. It's better to refer to what we're actually talking about, which is (acceptable) noise, or rather, SNR.

I guess I don't really understand this. At 200 or 300 mm, the background is going to be out of focus, if you are close to the subject, regardless of format. Odds are hummingbird pictures on full frame are going to be cropped down to below APS-C size anyway, meaning that your full frame has no effect in this situation. For wildlife, anyway, full frame gives almost no to no benefit.

[monochrome]

OPINION: Most of us don't need a FF camera to do anything we can't do reasonably similarly with APSc at its current level of technological development.

Pentax, however, IMHO and if they want to grow beyond a niche brand, needs a FF line of cameras for brand credibility with non-Pentax users, and to "be there" when Moore's Law drives FF sensor technology to commodity status (which will come sooner than any of us can imagine).

[ElJamoquio]

I guess I don't really understand this. At 200 or 300 mm, the background is going to be out of focus, if you are close to the subject, regardless of format.

I couldn't get all that close to the subject. An extra stop of DOF-reduction would've definitely helped.

Odds are hummingbird pictures on full frame are going to be cropped down to below APS-C size anyway,

Not really. My backyard is 15x30' ( a little less than 5x10 meters for you metric types) and I'm in the center of it.

[Rondec]

I couldn't get all that close to the subject. An extra stop of DOF-reduction would've definitely helped.




Not really. My backyard is 15x30' ( a little less than 5x10 meters for you metric types) and I'm in the center of it.

i took this photo:



with DA 55-300 at 300mm. I was a little less than 10 feet from the bird (shot at f7.1) and it still required a little better than a fifty percent crop. I just don't think for birding (or most wildlife) there is any benefit to full frame in any respect. Maybe your 300mm lenses are just longer than mine...

[pinholecam]

I don't think you have understood that correctly. To start with it would be more like 300 (not 100) on ff is the same as 200on apsc.

The difference in DOF that people are on about is the difference between the OOF areas produced by a 77/1.8(on ff) and a 50/1.8(on apsc). Both these set ups will have the same field of view. BUT the 77/ff image will have thinner DOF. (both setups would be in the exact same place)

I think that some people are deluded that the wider ff frame will make the bokeh better. It won't. The difference is made by using a different (longer) lens for the same shot. Thus producing a thinner DOF. Because we all know that the shorter the focal length is, the larger the DOF is. (as an example, a 15mm/f4 will have much more in focus (longer DOF) than a 300/f4). And to take a particular fov image on FF requires a 1.5ish-times longer focal length lens.

That is assuming that you want to stick to about the same subject to camera distance.
Juggle the options (ie. distance, FL, f-stop) and there is some 'play' that allows the photographer to get a 'like' photos for some focal lengths.

Personally, my observation is that for travels and in more unfamiliar places, a photographer tends to want a bit more DOF.
No point spending a chuck of cash to travel to France and take so many shots with so thin a DOF that it could have been one's own backyard.
More personal shots (ie. nearby gardens, family, friends, shots that don't matter than much and can be experimental (eg. streets; still life), less DOF is often chosen for isolation.

[ElJamoquio]

i took this photo:



with DA 55-300 at 300mm. I was a little less than 10 feet from the bird (shot at f7.1) and it still required a little better than a fifty percent crop. I just don't think for birding (or most wildlife) there is any benefit to full frame in any respect. Maybe your 300mm lenses are just longer than mine...

Sarcasm abounds.

My framing of the shots I've taken are different than yours; that should be obvious. I want to show some other features in the shot, but not show the background distinctly.

[normhead]

I couldn't get all that close to the subject. An extra stop of DOF-reduction would've definitely helped.

AN example with full exif might provide some other insight into your problem.

Sarcasm abounds.

Well actually a 300 mm lens that moves the front element in and out compared to a fixed length 300 mm lens will provide considerably more magnification at 10 feet. Maybe he was being sarcastic but, my SIgma 70-300 @ 7 feet and 135 mm, provides the same magnification as my 60-250 at 250mm. Not every 300 mm lens is equal for this type of shot. 300mm lenses (or any lens) will only produce consistent magnification at infinity. At 10 feet there are wide variations.

[ElJamoquio]

AN example with full exif might provide some other insight into your problem.

How so? I was as close to the subject as I could be, didn't want any further cropping, in some cases wasn't using all of the zoom range, and had more DOF than I would've liked. FYI I don't have permission to share, I could probably get it, but I'm not sure how it would help understand a fundamental technical limitation of APS-C when compared to FF.

Not every 300 mm lens is equal for this type of shot. 300mm lenses (or any lens) will only produce consistent magnification at infinity. At 10 feet there are wide variations.

OK; but I was comparing 'like' lenses, i.e. a FF vs APS-C. As long as they're similar (both primes, for example), your reminder is true but not a first order effect.

[cmohr]

You don't have permission to share pictures you took for fun of hummingbirds in your own backyard???? Thats funny.

[richard balonglong]

You must be joking. At F:1.4 you get so thin DOF on an APS camera with an 85mm lens that you can hardly get the whole face in focus.
I know professional protrait photographers. Their fastest lens is F:2.8....

I think you don't get it. An 85mm lens @ f/1.4 mounted on both aps-c and full frame and both have the same distance from the subject, it has the same dof but on the aps-c has only a tighter composition because of the crop factor.
And about pro portrait photographers, are you sure that their fastest lenses are at f/2.8 only? I don't think so. I've been working on portrait photography contracts and been along with top portrait photographers working for fashion magazines, the fastest lenses are always at f/1.2, and the slowest are always at f/2.8...

[Kryscendo]

To be honest, I have been planning on an APSC system of camera body and lenses and a FF system of camera body and lenses. I know you can use FF glass on APSC, but come on, even with Nikon or Canon, people who move up- often move up in big ways so they end up needing to purchase a new tele, or a new prime or two anyways.

[jsherman999]

Personally, my observation is that for travels and in more unfamiliar places, a photographer tends to want a bit more DOF.
No point spending a chuck of cash to travel to France and take so many shots with so thin a DOF that it could have been one's own backyard.
More personal shots (ie. nearby gardens, family, friends, shots that don't matter than much and can be experimental (eg. streets; still life), less DOF is often chosen for isolation.

You know, that sounds simplistic, but I find it to be true as well in my own personal shooting, which is probably part of the reason I travel with my aps-c kit as much or more than my FF kit. I'm usually not shooting in low-light as much when I travel, size matters a bit more, and I'm not isolating my subjects quite as often.... because I want more 'environment' in the shot when it's a new environment.

For example, these shots wer wide-open (35ltd @ f/2.8) because I needed the light, not because I wanted less DOF - in this case, a bit more DOF worked a little better to help define the background maybe a tad more:



In this one, however, I had hoped to retain the cloud structure while making the shoreline down there a bit more dreamy, removed, and the woman more isolated - 35mm @ f/2.8 on aps-c didn't quite get me what I was after, but I still like the flavor of the shot (35mm f/2.8):



On this one, I had been in Tennessee reading Civil War photography books all day and wanted to try some 'Civil war' looks out - or as close as I could get with what I had - and FF gave me a nice subject float here, from that distance and FOV (50mm f/1.8 on FF):



But of course, you can always stop down with FF if you do want to increase DOF (50mm f/8 on FF)