Cropping and Resolution on 40mp sensors

[jhorse]

Something that usually gets ignored in these discussions but is good to keep in mind, is that cropping makes noise more prominent. It's not as big an issue when working with a strong exposure, but as the available light diminishes and the resulting image moves closer to one's noise tolerance threshold, cropping may push the resulting image over the line.

Good point. I assume this applies regardless as to whether one uses an in-camera crop mode, such as I sometimes use on a X100VI, or in post.

It does. Cropping effectively reduces the sensor surface area used to capture light. As a result, less total light energy is used to make the photo and that makes noise more visible.

The stronger the exposure one works with, the less likely it is that noise will become obvious & annoying. But in low light, or when using an f-stop or shutter speed that significantly limits how much light is projected on the sensor, it's something to be mindful of.

Thanks.

 

[Bill Ferris]

Something that usually gets ignored in these discussions but is good to keep in mind, is that cropping makes noise more prominent. It's not as big an issue when working with a strong exposure, but as the available light diminishes and the resulting image moves closer to one's noise tolerance threshold, cropping may push the resulting image over the line.

Cropping digitally also results in less dynamic range I believe (maybe related). This was discussed in a thread about the new GFX100RF which has a dedicated cropping function as it's hallmark.

Yes. Dynamic range and noise are two sides of the same coin. Again, I don't want to overstate the impact in scenarios where the photographer is working with a quality exposure. It's something to watch for.

 

[Truman Prevatt]

Something that usually gets ignored in these discussions but is good to keep in mind, is that cropping makes noise more prominent. It's not as big an issue when working with a strong exposure, but as the available light diminishes and the resulting image moves closer to one's noise tolerance threshold, cropping may push the resulting image over the line.

Cropping digitally also results in less dynamic range I believe (maybe related). This was discussed in a thread about the new GFX100RF which has a dedicated cropping function as it's hallmark.

As Bill says, it does not increase the noise - the noise is already there. Cropping makes the noise more prominent because it decreases the total number of pixels the images is generated with. That is the magnification that is applied to the image through cropping magnification both the good pixels and the noise the same. In the case of strong light - not a big whop since you are dealing with a high SNR. In marginal lighting it can be an issue.

On the other hand I've not noticed it being a big issue with my Q2M. I had some shots at ISO 6400 indoors and I cropped about to about 20 MP out of the 47 and didn't see a visible increase in noise. One thing that gets lost in all of this is how large the final display vs. the crop. If you display a cropped image and an uncrossed image at the same size the cropped will not be as high quality because the magnification on the crop as displayed is larger than on the uncropped. It all gets down to enlargement ratio and magnification.

 

[Chuck Eklund]

And we don't all limit ourselves to online posts. Printing requires paying attention to dynamic range/noise among a host of other things.

 

[a_c_skinner]

It makes every defect more prominent. Down to enlargement. It will reduce DR in effect as shadow noise will be more noticable.

 

[KLO82]

Something that usually gets ignored in these discussions but is good to keep in mind, is that cropping makes noise more prominent. It's not as big an issue when working with a strong exposure, but as the available light diminishes and the resulting image moves closer to one's noise tolerance threshold, cropping may push the resulting image over the line.

Every 1.4x cropping is like using a one stop higher ISO. If you are shooting at ISO 3200, f2 and crop 1.4x from the entire frame, it is like using ISO 6400 and f2.8 (but also with half the number of pixels).

I like Fuji's idea of GFX 100. Start with a large sensor area and high megapixel, and you can forgo a zoom lens (up to some extent) while still composing your intended angle of view on viewfinder (unlike shooting and cropping in post process).

 

[CamerEyes]

In a current thread about the expected new X-E5 a contributor wrote:

"Cropping from 40MP to 20MP is exactly 1.4x focal length.

I wouldn't necessarily recommend buying 40MP 'in order' to crop, but it sure does help to have that extra information."

Actually, that's exactly one of the reasons I am considering one of the 40mp bodies, either the X-T50 or X-E5 once I know the specs of the latter. Long story short, I'm looking for a lightweight combo to complement my Sony RX10iv which is a great camera but hardly light or anywhere near jacket pocketable. Either would also allow be to add a pancake prime when wanting to go really light.

In my naivety I thought that a x2 crop in software after shooting would give me a focal length of 100mm and a resolution equivalent to 20mp. As pointed out this sort of crop would be equivalent to a focal length of 50 x 1.4 = 70mm. This still useful but a little more research shows me a 2x crop would mean 10mp resolution which is acceptable for some purposes but maybe not everyone's needs.

Overall I think the 40mp sensor and 16-50 will be a good option for a lightweight kit when I don't want or need the RX10iv and, if cropped, will still give me a decent size file, especially as I no longer print big or enter competitions.

I'm really just posting this for information for anyone considering a camera with higher resolution (whether Fuji or another) and I attach below a couple of results from my research. So if you're deliberating which sensor size (in MP) to select, maybe this will help.

John

p.s happy to be corrected if I've got anything wrong


From Jonas Rask's review of the X100vi clearing showing the drop in resolution when cropping.


From another discussion found on-line

Some of my clients are now requiring 30mp raw files. So having a 40mp raw file from my X-H2 is no longer "outlandish" no longer "excessive."

 

[Bill Ferris]

Something that usually gets ignored in these discussions but is good to keep in mind, is that cropping makes noise more prominent. It's not as big an issue when working with a strong exposure, but as the available light diminishes and the resulting image moves closer to one's noise tolerance threshold, cropping may push the resulting image over the line.

Every 1.4x cropping is like using a one stop higher ISO. If you are shooting at ISO 3200, f2 and crop 1.4x from the entire frame, it is like using ISO 6400 and f2.8 (but also with half the number of pixels).

Hmm, not so much.