September 19, 2014, 11:52:12 AM

Author Topic: Cropping, image quality and ISO.  (Read 993 times)

Mick

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Cropping, image quality and ISO.
« on: November 20, 2013, 03:42:17 PM »
Im not the most technical person around so I wondered about this question a friend asked about cropping and image quality.

If I have a full frame camera, an aps-c and aps-h and take the same shot with the same lens same light etc printed at the same size say A3, what would give the best image quality when taking say a shot in poor light...

The full frame shot at ISO3200 would need to be cropped so degrading the image quality, fine detail etc but has a two stop advantage over the aps-c and one stop over the aps-h who would need to shoot at higher iso to match the full frames speed so degrading the image quality. The aps-c needed no cropping but its ISO performance is worse and the aps-h mid way between the two. So I guess a 1DX, 1D4 and 70D for arguments sake. I said id use the full frame as id get the shot I wouldnt get with the others as the image quality would be so bad anyway without any cropping even with post production.

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Cropping, image quality and ISO.
« on: November 20, 2013, 03:42:17 PM »

neuroanatomist

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Re: Cropping, image quality and ISO.
« Reply #1 on: November 20, 2013, 04:02:14 PM »
Practically speaking, it would likely be a wash, assuming the sensors aren't too far apart in terms of technological age.  The cropped full frame image will have less noise, but the smaller sensor will put more pixels on target with the current higher pixel densities of those sensors.

For example, I previously did a comparison between my 7D and my 5D2.  I found that the 7D image appeared noisier than the 5D2 image but also had more fine detail.  The differences were small enough that noise reduction on the 7D image (which would reduce sharpness) or sharpening of the 5D2 image (which would increase perceived noise) would give equivalent results.

The difference is that if you don't have to crop the full frame image, you will definitely get better image quality.   You also have the flexibility to choose a shallower depth of field if you want that.
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Mick

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Re: Cropping, image quality and ISO.
« Reply #2 on: November 20, 2013, 04:17:05 PM »
Thanks Neuro. Just out of interest, if a current 1DX, top full frame, current top APS-C 70D and older 1D4 were tried out, my guess would be as you put it similar with the cropping.

Also Neuro, ive just bought a 1DX for my 500. Have you noticed you use APS-C a lot now? Do you miss that 1x6 crop?

Mick
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neuroanatomist

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Re: Cropping, image quality and ISO.
« Reply #3 on: November 20, 2013, 04:21:26 PM »
Thanks Neuro. Just out of interest, if a current 1DX, top full frame, current top APS-C 70D and older 1D4 were tried out, my guess would be as you put it similar with the cropping.

Also Neuro, ive just bought a 1DX for my 500. Have you noticed you use APS-C a lot now? Do you miss that 1x6 crop?

I think you'd see the same thing, yes.

I stopped using my 7D altogether, and subsequently sold.  I don't miss it a bit.
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Re: Cropping, image quality and ISO.
« Reply #4 on: November 20, 2013, 07:53:10 PM »
Im not the most technical person around so I wondered about this question a friend asked about cropping and image quality.

If I have a full frame camera, an aps-c and aps-h and take the same shot with the same lens same light etc printed at the same size say A3, what would give the best image quality when taking say a shot in poor light...

The full frame shot at ISO3200 would need to be cropped so degrading the image quality, fine detail etc but has a two stop advantage over the aps-c and one stop over the aps-h who would need to shoot at higher iso to match the full frames speed so degrading the image quality. The aps-c needed no cropping but its ISO performance is worse and the aps-h mid way between the two. So I guess a 1DX, 1D4 and 70D for arguments sake. I said id use the full frame as id get the shot I wouldnt get with the others as the image quality would be so bad anyway without any cropping even with post production.

The solution is to use the right lens if you are serious about IQ.   Only if you are focal length limited would you purposely use a wide lens and crop to APS-C size.

I will crop if my 400mm plus 1.4X TC is not long enough, or if I have seconds to get a shot off and must use whatever lens is on the camera. 

The person also needs to consider the converse, What would he do if he used the same lens on a APS-C or APS-H camera that filled the Frame on his FF Body?  He might not be able to do anything to recover the image.  I'm only pointing this out, because in reality, its not something a photographer would do, he'd get the right lens, or move forward or backwards.


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Re: Cropping, image quality and ISO.
« Reply #4 on: November 20, 2013, 07:53:10 PM »