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Puzzling pixel dimensions


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Hi

Here's a thing.

I set my camera (Canon Powershot SX60 HS) to record both JPG + CR2 (RAW) and shoot.

Load both resulting pics into Photo and look at the information bar at the top I find the following:

 

Image_5391.JPG

4608 x 3072px, 14.16MP RGBA/8

 

Image_5391.CR2

4672 x 3500px, 16.35MP, RGBA/16

 

If I look at the image properties in Windows File Exlorer - Properties/Details I find:

Image_5391.JPG

Dimensions: 4608 x 3072

 

and for the RAW image:

 

Image_5391.CR2

Dimensions: 4608 x 3072

 

(This is with no editing of the RAW file in Develop Persona)

 

This has me puzzled.

Any suggestions?

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Hey D23, this is because the SerifLabs raw engine doesn't look at crop information when decoding the raw file. To explain:

 

In-camera JPEG processing discards edge pixels because it's more computationally expensive to interpolate them. Therefore, for parity, crop instructions are written into the exif data of the raw files so that the decoded raw image can be cropped to match. Because the SerifLabs engine ignores these crop instructions, you'll often find the X and Y dimensions of a raw file gain anything from 30 to 90 pixels extra (this is referring to the majority of DSLRs and CSCs).

 

Most of the time this is fine, but I'm aware that the Powershots are an odd case. Either the lens's image circle doesn't appear to fully cover the sensor, or the lens exhibits some quite strong vignetting and distortion at the edges - hence why it is usually cropped off. In your case there seems to be excess vertical resolution. Out of interest, if you open a raw file in Photo, what's at the top and bottom of the image? Is it mostly vignette/distortion or does it seem usable?

 

The other use case for cropping information in the exif data is if your camera has different aspect ratios like 4:3, 3:2, 16:9, 1:1 etc. Unless your camera has a multi-aspect sensor (e.g. the Panasonic GH2 and GH1), all these ratios do is simply crop the image from its original aspect ratio. If you're shooting JPEG, this crop is performed destructively in camera. If you're shooting raw, however, the entire image is still written, and instead it's up to the raw processing software to apply the crop. In this case, Photo doesn't.

 

Apologies that all I can offer at the moment is a long-winded explanation! I do think it would be a good idea to have a configurable exif crop option so that users have a choice, and will mention this to the developers.

 

Hope that helps!

Product Expert (Affinity Photo) & Product Expert Team Leader

@JamesR_Affinity for tutorial sneak peeks and more
Official Affinity Photo tutorials

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Out of interest, if you open a raw file in Photo, what's at the top and bottom of the image? Is it mostly vignette/distortion or does it seem usable?

Thanks.

For a photo shot in 16:9 the only thing noticeable at the top & bottom (& sides) is a shaded border about 16 pixels width. Other than that it's fine.

A photo shot in 4:3 exhibits nothing noticeable.

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