p.2 #1 · Does the crop mode on A7R III give me more depth of field?
hsiunghsiung wrote:
Bringing this question back just in case.
So an a7riii with a 35mm f1.8 lens in aps-c/s35 mode will shoot like a 52.5mm focal equivalent at f2.8 depth of field equivalent if the subject is in the same place right?
Ex:
The image will look the same in terms of composition and depth of field with subject in the same exact location from the camera:
-An a7riii (in aps-c mode) + 35mm f1.8
-An a7riii (in FF mode) using a 52.5mm f2.8 lens (theoretical lens).
p.2 #3 · Does the crop mode on A7R III give me more depth of field?
hsiunghsiung wrote:
let's just say roughly f2.7/2.8, but besides that detail, the example with those two setups will have similar look right?
Yes, it will be very similar. You might notice the flaws if you put the same in crop mode as it’s more demanding resolution wise (I generally see more axial CA and SA as well) but you’re also not using the outer 1/3 (or so) or the lens where things can fall apart more on FF (vignetting, sharpness, coma, bokeh).
But yes, in terms of FOV and DOF it will be very similar.
p.2 #5 · Does the crop mode on A7R III give me more depth of field?
mawz wrote:
The difference between APS-C and FF is also slightly over 1 f-stop (it's 1.5 crop, 1.414 crop would be 1 stop exactly)
That said, 35/1.8 is equivalent to 52.5/2.7
35/2 however is equivalent to 52.5/3 not 2.8
I don't doubt you're wrong, but how are you arriving at that precise number? I have always heard/seen it as 1.5, though I understand it's an estimate I guess.
p.2 #6 · Does the crop mode on A7R III give me more depth of field?
nehemiahphoto wrote:
I don't doubt you're wrong, but how are you arriving at that precise number? I have always heard/seen it as 1.5, though I understand it's an estimate I guess.
The aperture whole stop series is a root 2 progression and the square root of 2 to 3 decimal places is 1.414
You can easily check this. Multiply any whole aperture value by 1.414 and round to 1 decimal place and you'll get the next full stop value. Past f5.6 round to whole numbers (like shutter speed, there's a few discontinuities in the printed values to make the numbers more intelligible)
As to the rest, a 35/2 has a 17.5mm physical aperture. 35*1.5 is 52.5 and 52.5mm/17.5mm is 3
35*1.414 is 49.49 and 49.49/17.5 is 2.8 rounded to 1 decimal place. That means a 1.414 crop value would give f2.8 equivalent from a 35/2
This is also why we have 1.4x TC's and not 1.5x ones. 1.4x gives 1 stop penalty.
It should be noted that non-Canon APS-C crop actually drifts between 1.52x and 1.56x depending on the exact sensor used. It's referred to as 1.5x for convenience.
p.2 #7 · Does the crop mode on A7R III give me more depth of field?
mawz wrote:
The aperture whole stop series is a root 2 progression and the square root of 2 to 3 decimal places is 1.414
You can easily check this. Multiply any whole aperture value by 1.414 and round to 1 decimal place and you'll get the next full stop value. Past f5.6 round to whole numbers (like shutter speed, there's a few discontinuities in the printed values to make the numbers more intelligible)
As to the rest, a 35/2 has a 17.5mm physical aperture. 35*1.5 is 52.5 and 52.5mm/17.5mm is 3
35*1.414 is 49.49 and 49.49/17.5 is 2.8 rounded to 1 decimal place. That means a 1.414 crop value would give f2.8 equivalent from a 35/2
This is also why we have 1.4x TC's and not 1.5x ones. 1.4x gives 1 stop penalty.
It should be noted that non-Canon APS-C crop actually drifts between 1.52x and 1.56x depending on the exact sensor used. It's referred to as 1.5x for convenience....Show more →
Excellent answer and explanation. I knew about the teleconverters and the focal length, but I didn’t understand the underlying math or know the exact aperture multiplier. Thanks again.
p.2 #8 · Does the crop mode on A7R III give me more depth of field?
For the heck of it I wanted to see how good the IQ was by using A7rIII + 200-600 + 1.4 + crop mode
Is my math correct? Am I shooting @ 1260mm, and what would be the MP count ?
p.2 #9 · Does the crop mode on A7R III give me more depth of field?
IndyFab wrote:
For the heck of it I wanted to see how good the IQ was by using A7rIII + 200-600 + 1.4 + crop mode
Is my math correct? Am I shooting @ 1260mm, and what would be the MP count ?
p.2 #10 · Does the crop mode on A7R III give me more depth of field?
According to Norman Koren (the inventor of the Imatest lens testing software), the idea that smaller formats have greater depth of field is a myth: why? because any apparent increase in DOF of the smaller formats is lost, because they have to be enlarged more compared to larger formats; that is to say, for the same sized print, there is no difference in DOF between the formats.
