24-200mm + Z5 JPEGs not using full sensor area

Started 4 months ago | Discussions
Kenneth Almquist Regular Member • Posts: 140
24-200mm + Z5 JPEGs not using full sensor area

I shot the picture here with the Z5 set to raw+jpeg mode.  The first picture below is the out of camera JPEG and the second is a raw conversion.  There are two reasons I know of why all of the pixels in a raw image may not show up in the JPEG.

First, demosaic algorithms are simpler if they don't have to deal with the edges of images.  In the case of the Z5, the sensor is 6040x4032 pixels, but the JPEG images are only 6016x4016 pixels.  I converted the raw image using dcraw which can demosaic the entire raw image including the edges, but I cropped off the extra pixels to get a 6016x4016 image, the same size as the JPEG.

Second, the Z5 corrects for lens distortion, which will cost a few pixels because correcting lens distortions results in a non-rectangular image which then has to be cropped to get it rectangular again.  The Z5 allows you to turn off distortion correction for some lenses, but not for the 24-200mm lens.

However, the out of camera JPEG shown is missing more of the raw image than would be lost by distortion correction.  The camera is in effect performing a crop in addition to the distortion correction, and then scaling the image to get back to 6016x4016 pixels.

I initially spotted this in a shot taken at the 200mm focal length and thought this might be Nikon pretending that the lens had a maximum focal length of 200mm when it actually fell slightly short., but the shot below is at the 49mm focal length.

Out of camera JPEG

Raw conversion

This isn't a huge deal, but it did surprise me, and it means that unless you shoot raw you are getting slightly fewer usable pixels from the camera than you might expect.

 Kenneth Almquist's gear list:Kenneth Almquist's gear list
Nikon D7200 Fujifilm X-H1 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF-S DX Nikkor 18-300mm F3.5-6.3G ED VR Fujifilm 16-55mm F2.8R LM WR +2 more
Eric Calabros
Eric Calabros Regular Member • Posts: 194
Re: 24-200mm + Z5 JPEGs not using full sensor area

If this is the case, it shouldn't crop at say 100mm. Zoom lenses have the least amount of distortion at the middle of the range.

Anyway its apparently the cost we're paying for edge sharpness in compact package. Nearly all Z zoom lenses patents I see have huge vignetting wide open and a lot of distortion.

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