topic Re: Canon Rebel T7 - Varying Image Dimensions in EOS DSLR & Mirrorless Cameras

Canon Rebel T7 - Varying Image Dimensions

applegaa — Tue, 14 Nov 2023 01:36:03 GMT

Why does the T7 produce images with a variety of dimensions instead of a fixed size? I thought that the image dimensions were determined by the sensor size and would be consistent. But, here's a sampling of the dimensions I've seen in tonight's batch:

6027 x 4018,

6015 x 4010,

6120 x 4080,

5935 x 3957

Re: Canon Rebel T7 - Varying Image Dimensions

kvbarkley — Tue, 14 Nov 2023 02:34:36 GMT

Because of the bayer array, there are more raw pixels than JPEG pixels, and processing can be a bit variable with the handling of these. If you want consistent sizes, you need to shoot JPEG.

Re: Canon Rebel T7 - Varying Image Dimensions

Peter — Tue, 14 Nov 2023 03:04:44 GMT

Lens correction turned on?

Re: Canon Rebel T7 - Varying Image Dimensions

applegaa — Tue, 14 Nov 2023 03:30:47 GMT

That still doesn't make sense to me. If it can handle x number of pixels one time, why can't it handle that same x number of pixels another time? RAW is supposed to straight from the sensor and the number of pixels on the sensor doesn't change between shots just because their recorded values change, so it should be consistent.

That said, I'm not saying your wrong. I'm just saying it doesn't make sense to me. It's also disappointing that I can't create an improved version of the 6000 x 4000 JPEG file that my camera created because the RAW file is only 5935 x 3957.

Re: Canon Rebel T7 - Varying Image Dimensions

Peter — Tue, 14 Nov 2023 20:01:24 GMT

Open your raw file in darktable, go to active modules and the module raw black/white point. Go to its hamburger menu and hit passthrough. Now you will see the whole sensor area including the hidden optical black area. The image will look dull, so if you want a normal look with optical black area you need to set the three black points to 2048 and the white point to 12277 for ISO 100 or 15092 for everything else.

6096 x 4051 px for your T7, including the masked area.

Why the different sizes? Well, some things need to be done, like:

Optical black area needs to be cropped out. It should be something like 70 columns from left and 34 lines from top for your camera.
The borders need to be cropped a little bit. A few columns and lines. darktable removes 8 columns from left, 8 lines from top, 4 columns from the right and 6 lines from the bottom.
Distortion correction will crop even more depending on lens.

Re: Canon Rebel T7 - Varying Image Dimensions

applegaa — Tue, 14 Nov 2023 14:52:41 GMT

I enable the Distortion option under lens correction as part of my default recipe. Sure enough, if I disable it, the raw images return to their 6000 x 4000 dimensions, matching the out-of-the-camera jpegs.

Thank you!