F stops!

bartjeej

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bart
It makes up SOME with high ISO sensitivity, but only a stop or so over the best of APS (I shoot the RX1 waaaaaay beyond 3200, usually topping out at 12,800 for street work, but I shoot the Nikon A at 6400, so about a stop), and I'd say it loses a lot more than a stop of DOF, for lack of a better way to characterize it. The RX1 has to shoot at f8 to get close to the DOF I get from the Nikon A at f3.5, so that's about two and a half stops of exposure, which is more than the better sensor can compensate for.


Edit - Bart, I think this addresses your post as well...

-Ray

True, but only about 1 stop of that DOF difference is down to the sensor size difference; the rest is due to the difference in equivalent focal length. If you'd compare FF and APSC at equivalent focal lengths (as I indicated in my post above), my point still holds: in terms of deep DOF, there're no disadvantages to shooting FF, but there are advantages for shallow DOF.
 

Ray Sachs

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you should be able to figure it out...
True, but only about 1 stop of that DOF difference is down to the sensor size difference; the rest is due to the difference in equivalent focal length. If you'd compare FF and APSC at equivalent focal lengths (as I indicated in my post above), my point still holds: in terms of deep DOF, there're no disadvantages to shooting FF, but there are advantages for shallow DOF.

When you say "equivalent focal length", do you mean actually equivalent (ie, 24mm on full frame and 24mm on APS, which would be more like an effective 36 on APS) or do you mean the same effective focal lengths giving the same field of view (ie 24 on full frame and 16 on APS, which is an effective 24 on the APS)? For sure, if you mean ACTUALLY equivalent, there's no difference between DOF with full frame, APS, m43, or anything else at equivalent apertures. But then you're dealing with fairly radically different effective focal lengths or fields of view. I like to shoot on the street within a fairly narrow range of effective focal lengths, so I'm gonna get more depth of field with APS than full frame and more yet with m43 at roughly equivalent fields of view.

-Ray
 

Luckypenguin

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I'm guessing what Bart in getting at is that in theory you can afford to stop a lens on a FF camera down one more stop than one of equal field-of-view on an APS-C camera to equalise depth-of-field, and rely on the FF cameras greater ISO performance (theoretically one stop) to get a similar end result.
 

Ray Sachs

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Probably. But most DOF calculators show nearly a two stop difference to equalize DOF at the most common settings I tend to use and I'm comfortable shooting APS within one stop or less of ISO sensitivity of full frame (the RX1 at least - maybe the D4/Df sensor would give me more), so I'm still getting a doubling of the shutter speed for roughly the same DOF with APS. Which is meaningless in good light, maybe even decent light, but in low light it matters...

-Ray
 

bartjeej

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^ most DOF calculators would be wrong, then :p
I was talking about equal field of view. Your Nikon A with its 18.5mm f/2.8 on APSC will have roughly the same DOF (and exactly the same field of view) as 28mm f/4.2 on FF*, and also the same DOF as your RX1's 35mm at f/6.7 (ignoring the not-quite-35mm-thing). As you can see, only about 1 stop of the difference is caused by the different sensor size; the rest is down to the difference in field of view.

So if you had a FF camera with a 28mm lens and you stopped it down to f/4.2, and upped the ISO by just over 1 stop, then you'd have the same DOF, same shutter speed, and same sensor output as your Nikon A at f/2.8.

*the reason that it's just a bit more than a stop is because APSC is just a bit more than one stop smaller than FF
 

Ray Sachs

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you should be able to figure it out...
^you're right, this has gone on longer than it should have, and it's not THAT important either. Guess I'm still in thesis mode:redface:

Screw 'em - they're free to not read it if they find it so boring. I'll close with this link from another thread, just recently re-activated that I'd all but forgotten about, where Amin makes the same fundamental point I'm trying to make regarding the RX1 and X100s. It's academic and boring unless it's a specific detail that affects how you shoot, in which case it can be quite interesting, or at least important to work out... I've shot with all of it - I friggin LOVE full frame in the form of the RX1 for a LOT of shooting. For street shooting I prefer a smaller sensor, all other things being roughly equal.

https://www.photographerslounge.org/showthread.php?t=18002&page=3&p=121965#post121965

-Ray
 

bartjeej

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^the funny thing is, that Amin is saying exactly what I'VE been trying to say, too:laugh1:
for the same DOF, the ISO 16000 RX1 shots 'probably aren't gonna be much nicer than the X100 ISO 6400 files'. Not much nicer, but no worse either - eg, about the same. So, no disadvantage to shooting the FF sensor.
 

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