Continuation: Sensor Size, Present & Possibilities

Started Apr 10, 2013 | Discussions thread
EinsteinsGhost
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Re: On DOF
In reply to joejack951, Apr 10, 2013

joejack951 wrote:

EinsteinsGhost wrote:

joejack951 wrote:

EinsteinsGhost wrote:

joejack951

Even if it is "most of the time" (and that's highly debatable) how is it an advantage to not be able to go more shallow with DOF as you can with full frame? There's nothing stopping you from stopping the lens down on full frame after all to get the same DOF as APS-C.

The FF advantage on shallower DOF is primarily at wide angles.

No, it exists at all focal lengths. For any given field of view and aperture used, FF has an advantage when trying to minimize DOF. Smaller systems suffer even more at the extremes because there aren't as many high end lens choices there as there are for FF.

With APS-C sensor, and faster lenses, I usually end up ensuring proper DoF while maintaining a good isolation. That is the beauty of being able to control DoF.

Yes it is, and you get even more control with FF. Try matching a 24mm f/1.4 on FF (a combination that even wide open has a good amount of DOF) with a crop camera.

Provide me with a photograph you've taken with such combination so we have something to work with.

The following image has no value but only to demonstrate DOF, which is barely "a fly deep":

You've demonstrated the one place where the add DOF of a smaller format can be an advantage: close up/macro photography. At a larger distance to subject, the more shallow DOF of FF can be very welcome.

You do realize the point I made, that the same lens on FF would have a deeper DoF at the same distance, no?

Uncropped, yes. Cropped to the same framing, they'd be identical. Moving closer with the FF camera to match the APS-C framing, it would be more shallow.

So, to match or beat an APS-C DoF achieved optically, you'd have to digitally crop the image out of FF, right?

And that is APS-C. The same lens on 35mm sensor will actually have a deeper DoF due to a wider FoV.

Only if you didn't move any closer to keep the subject framing the same (in which case, assuming you were not limited by minimum focus distance, you'd have less DOF in the FF shot). If you cropped the FF file to match the APS-C image, you'd have the same DOF.

You would have to move closer with FF (if the lens' minimum focusing distance allows) to get the same framing and DoF in that case.

You are confused. Everything held equal, cropping a FF file to an APS-C file's framing yields the same DOF. As soon as you start moving closer with the FF camera (and cropping less up to the point where no crop is needed), the FF shot will have less DOF. Go try for yourself at www.dofmaster.com

The only confusion there is about you not being able to differentiate between digital cropping (FF file) versus optical results out of APS-C.

But yes, there is nothing stopping one down from stopping down. In fact, stopping down is pretty much needed under most circumstances. I almost never shoot with a fast lens wide open but on rare occasions (usually, lighting):

That is comparable to 50mm f/2.8 on FF.

And you'd be s*** out of luck if you wanted the equivalent of a 50mm f/1.4 on full frame.

There is no need for that. This was taken with NEX-3 and 35mm f/1.8 lens (wide open):

Why exactly would you need 50mm f/1.4 on FF?

Is this a serious question?

Yes. What would you use 50mm f/1.4 on FF for a similar situation? Would it be to lessen the isolation effect, or to improve it? For that matter, do you always shoot wide open?

And that takes us to another issue. Stopping down can sometimes necessitate higher ISO which would take away, most if not all, DR and noise advantage of FF.

Yes, it most certainly does. But as I also pointed out, not all lenses are f/1.X or even close. An f/4 zoom on FF is the equivalent of an f/2.7 zoom on APS-C. If you often shoot that APS-C zoom wide open, you could have much more range (reference typical APS-C f/2.8 zooms that range from 16-50 or similar and FF f/4 zooms that go from 24-120) at the same quality (actually a little better depending on the camera being compared).

If you get sufficient DoF at f/1.x, you won't need to stop down. This happens with smaller sensors or shorter focal lengths (as in the illustration above). With APS-C, it is not uncommon for me having to stop down to f/4 or so, to get enough DoF. Do you always have to shoot wide open at f/1.x to get sufficient DoF?

There are times when wide open at f/1,4 on full frame (or wide open at f/2.8 or f/4 depending on the lens) that I wish I had less DOF, or am happy with the amount I have. Using an APS-C camera would then mean that I'd have more DOF than I desired.

Give me an example.

Why is it so hard for you to understand that, as perfectly illustrated above with your pictures and question about necessity of a 50mm f/1.4, just because you are happy with your APS-C results doesn't mean that everyone else has to be?

This isn't about trying to make you happy, or sad. This is about discussing pros and cons of systems.

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