[Rondec]

Keeping all variables equal except sensor size which has more DoF?
85mm lens
F/4.0
10' subject distance


What is the DoF the K-3? FF? 645z?

I don't understand the question. I suppose the K3 probably has the least depth of field, but I always assume the same framing between shots, otherwise the exercise feels pretty futile to me. Keeping the same framing between shots means either using a different focal length (55-ishmm on APS-C) or backing up considerably.

[Pål Jensen]

I don't understand the question. I suppose the K3 probably has the least depth of field, but I always assume the same framing between shots, otherwise the exercise feels pretty futile to me. Keeping the same framing between shots means either using a different focal length (55-ishmm on APS-C) or backing up considerably.

The problem is that some insist on normalizing everything to FF, hence excluding whatever properties other formats have, and thereby treat is as if such properties has no relevance. But if you turn this on its head and try to normalize everything to APS, you end with things FF cannot do; it is equally, if not more relevant.
It is true that FF will have about a stop less DOF at some focusing distances, but at others it won't and at some again it can't shoot anything in focus.

Now which lens will show the thinnest DOF at close focusing distance when the lenses (same type of lenses; prime vs. prime etc) show the same angle of view on their respective formats and shot at the same aperture; APS or FF?

[Winder]

I don't understand the question. I suppose the K3 probably has the least depth of field, but I always assume the same framing between shots, otherwise the exercise feels pretty futile to me. Keeping the same framing between shots means either using a different focal length (55-ishmm on APS-C) or backing up considerably.

You are changing multiple variables and saying APS-C has more DoF and that is false.


It is the 55mm lens that you switch to that is giving you the DoF of a 55mm lens and the FoV of an 85mm lens. Its not the sensor.

[Rondec]

You are changing multiple variables and saying APS-C has more DoF and that is false.


It is the 55mm lens that you switch to that is giving you the DoF of a 55mm lens and the FoV of an 85mm lens. Its not the sensor.

Really.

The whole point of photography is the image. To me, that means maintaining a certain framing of your subject in comparison shots. Whether you want to achieve that by backing up, or switching lenses is immaterial to me. I just think that if you have nice framing with your full frame capture, you will have an odd composition when you maintain everything else the same, but switch to a crop sensor.

That said, I think for whatever reason people focus on the extremes with regard to aperture, where I seldom shoot. I just don't shoot with an aperture wider than f2 and certainly don't stop down past f11. If someone else does, than they are more likely to see differences when they are using a full frame camera.

---------- Post added 04-04-15 at 11:56 AM ----------

The problem is that some insist on normalizing everything to FF, hence excluding whatever properties other formats have, and thereby treat is as if such properties has no relevance. But if you turn this on its head and try to normalize everything to APS, you end with things FF cannot do; it is equally, if not more relevant.
It is true that FF will have about a stop less DOF at some focusing distances, but at others it won't and at some again it can't shoot anything in focus.

Now which lens will show the thinnest DOF at close focusing distance when the lenses (same type of lenses; prime vs. prime etc) show the same angle of view on their respective formats and shot at the same aperture; APS or FF?

This is of course true. You can't always get "equivalent" photos between formats. You will be able to frame a lot tighter on an APS-C camera at close focus distance, than on a full frame camera. While the theory assumes that everything you can do on APS-C you can do on full frame, you just need the "right lens."

[ElJamoquio]

Surely in many situations with FF you could double the shutter time instead of increasing the ISO after stopping down to obtain the same DOF on FF as on APS-C? Of course this would often bring too many problems but there must be a fair portion of situations in which it would be fine.

Then you could double the shutter time of the APS-C camera too.

---------- Post added 04-04-15 at 09:17 AM ----------

But if you turn this on its head and try to normalize everything to APS, you end with things FF cannot do

Your premise is false. I have never taken a photo on, say, my K-5 that I couldn't also take with the A7R. The A7R is a superset of the APS-C capability.

[jsherman999]

Really.

The whole point of photography is the image. To me, that means maintaining a certain framing of your subject in comparison shots. ... I just think that if you have nice framing with your full frame capture, you will have an odd composition when you maintain everything else the same, but switch to a crop sensor.

Correct, and I'm not sure why that's so hard to understand. What's the point of worrying about "DOF differences" if the framing, the shot itself is radically different to start with?

The same lens on two formats from the same position gives you a very different image. Any DOF difference there is moot and the last thing anyone would recognize as 'different' about the two images.

That said, I think for whatever reason people focus on the extremes with regard to aperture, where I seldom shoot. I just don't shoot with an aperture wider than f2

Here's the best thing for you to do when you move to FF: just leave all your settings (besides FL) the same, just worry about exposure and shutter speed and framing as normal, and take what you get - and what you will get is the same images with 1.3 stops less DOF and about a stop better DR and noise (up from base ISO where it would be noticed, at least.) So you would't need to change anything, you could just realize the benefits.

When you run across a situation where you need more DOF, matching what you were used to with aps-c, simply stop down and you match the DR/noise of aps-c, and you will probably gain a little lens sharpness and contrast. f/1.8 vs f/2.8 or f/2.8 vs. f/4.5 on most lenses makes a noticeable difference.

So there ^ you have,

1) better DR/noise with 1.3 stops less DOF, *or* if you need to 'match DOF' and stop down,
2) same DR/noise with 1 stop better sharpness/contrast (at mid to high apertures at least.)

In addition to the above benefits, you're seeing the image magnified less, so the lens probably will seem slightly 'sharper' than you gave it credit for before, and you'll have a better VF, probably faster AF lock and more accurate AF, resulting in even more keepers... A newer/better body (presumably) used to get those better-IQ images.

That's it. Shoot like before, don't worry about it, adjusting FL only. See what you get. I'm 90% certain you'll like what you see more than before, and as time goes on you'll have a hard time giving up the difference.

.

[Pål Jensen]

Your premise is false. I have never taken a photo on, say, my K-5 that I couldn't also take with the A7R. The A7R is a superset of the APS-C capability.

Thats fine, but what you have or have not shot is irrelevant in this discussion.
You CAN shoot images on APS that you cannot do on FF with "equivalent" lenses and that is important when you compare formats.
Whats relevant is up to the user.

[Winder]

The whole point of photography is the image. To me, that means maintaining a certain framing of your subject in comparison shots. Whether you want to achieve that by backing up, or switching lenses is immaterial to me.

Then use your 15mm as a portrait lens and just get close enough to keep the framing the same and see what happens. A 55mm lens can never render like an 85mm lens any more than a15mm lens can render like an 85mm. Different focal lengths render scenes differently. There more to lens selection than FoV.

[mecrox]

So there ^ you have,

1) better DR/noise with 1.3 stops less DOF, *or* if you need to 'match DOF' and stop down,
2) same DR/noise with 1 stop better sharpness/contrast (at mid to high apertures at least.)

In addition to the above benefits, you're seeing the image magnified less, so the lens probably will seem slightly 'sharper' than you gave it credit for before, and you'll have a better VF, probably faster AF lock and more accurate AF, resulting in even more keepers... A newer/better body (presumably) used to get those better-IQ images.

That's it. Shoot like before, don't worry about it, adjusting FL only. See what you get. I'm 90% certain you'll like what you see more than before, and as time goes on you'll have a hard time giving up the difference.

.

Yes, keep it nice and simple and enjoy any advantages from what you get, since there are advantages. I am sure this is the best approach, not making comparisons all the time.

[Pål Jensen]

Then use your 15mm as a portrait lens and just get close enough to keep the framing the same and see what happens. A 55mm lens can never render like an 85mm lens any more than a15mm lens can render like an 85mm. Different focal lengths render scenes differently. There more to lens selection than FoV.

Thats right. There is in reality no true equivalence.

[ElJamoquio]

Thats fine, but what you have or have not shot is irrelevant in this discussion.
You CAN shoot images on APS that you cannot do on FF with "equivalent" lenses and that is important when you compare formats.
Whats relevant is up to the user.

If you provide an example, I will be happy to point out the error in your example.

---------- Post added 04-04-15 at 10:01 AM ----------

Then use your 15mm as a portrait lens and just get close enough to keep the framing the same and see what happens.

Your implication is true.

A 55mm lens can never render like an 85mm lens any more than a15mm lens can render like an 85mm. Different focal lengths render scenes differently. There more to lens selection than FoV.

If you allow different sensor sizes, your example is false. With equivalent settings, equivalent lens design, equivalent tolerances, etc., the two pictures will be indistinguishable.



(unless you're looking at quantum lengths, and I don't think your eyes can do that)

[osv]

You CAN shoot images on APS that you cannot do on FF with "equivalent" lenses and that is important when you compare formats.

so where are the examples of this phenomenon?

[jsherman999]

so where are the examples of this phenomenon?

Crickets.

Actually he'll probably give a long-telephoto example and then declare it against the rules to simply choose a telephoto 1.5 longer on FF.

[Winder]

With equivalent settings, equivalent lens design, equivalent tolerances,

Which 15mm has an equivalent lens design to an 85mm and we will compare.

[normhead]

Your premise is false. I have never taken a photo on, say, my K-5 that I couldn't also take with the A7R. The A7R is a superset of the APS-C capability.

Yes but you don't shoot telephoto... if you shoot all three lens lengths, telephoto, wide and standard, you might choose a different set of compromises. Your A7r only shoots 15 Mp in the crop area, a K-3 shoots 24 MP. So whatever your longest lens is, it would seem 1.5 times longer with a K-3, and you'd get about 20% more resolution doing on a subect that fits within the crop area, using the K-3. Which is why so many people who shoot wildlife, Nikon as well and Pentax, shoot crop sensors with their long lenses. Many of the shooters I know who have both use their APS-c for bird and small mammal images.

On many of our images we are cropping APS-c images. When you end up with a 7 MP image shooting full frame and I have a 12 MP image using a K-3, you're going to see a difference, and it's possibly going to be the difference between a saleable print and one that just looks good web size. People have experienced this.