Continuation: Sensor Size, Present & Possibilities

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

joejack951 wrote:

EinsteinsGhost wrote:


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.

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?

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.

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?

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?

Personally, I find APS-C as the best compromise between larger and smaller sensors. That is not to say that I don't see a point to FF.

When you state it that way, there's nothing to argue about

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