APSC lens with a full frame sensor - variable aspect ratio

[KitW]

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Following the recent speculation about a putative CL2 being introduced after all, but with a full frame sensor... I was wondering how beneficial it would be if you could set a variable aspect ratio when using an APSC lens on a full-frame body. I did two simulations to help visualise the gains you might expect. I imagine this is already out on the internet somewhere, but I didn't find it so made my own version.

The first picture is a random full-frame image, cropped to APSC as if taken with an APSC lens.

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Edited February 13, 2024 by KitW

[KitW]

The animated picture shows how the total area of the crop changes between a panoramic crop (1/3 the height of a normal APSC landscape crop), passing through a square crop, to a vertical APSC crop. The assumption is that it is acceptable to crop to the same circumferential margin for any given crop. Obviously if you cut the bottom and top 1/3s of the image off, you end up losing a lot of the pixels. However, you gain a reasonable percentage laterally. The lateral bar graph shows the area of the crop as a percentage of the area of the full-frame.

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Edited February 13, 2024 by KitW

[KitW]

The third picture/animation shows how the areas of the crops change:

1. In white, a full frame sensor cropped to various aspect ratios between 9:2 and 2:3
2. In green, a full frame sensor optimally cropped to maximise the area obtainable with a given aspect ratio
3. In red/yellow, an APSC sensor cropped in the same way as the full frame sensor

There is always a benefit to being able to choose a custom crop - in some cases significant. This is particularly the case for a square crop (64% more pixels than the APSC crop; 28% wider/higher), but even in the panoramic crop you end up with a significantly wider image (17%). For the square crop, the optimised crop is only 25% narrower than full frame (2/3 the pixels) of full frame.

Perhaps it's not earth shattering, but for something that is just software it seems a shame to pass it up...

I have bigger versions of the animation available, but these are the biggest I can upload to this website.

 

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Edited February 13, 2024 by KitW

[KitW]

Less vignetted versions of the first two files:

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[jaapv]

Very nice and clear. It would help if we knew the actual coverage circle of the lens, which can be considerably larger and switch off the automatic crop in the camera. 

[dpitt]

13 hours ago, KitW said:

The third picture/animation shows how the areas of the crops change:

1. In white, a full frame sensor cropped to various aspect ratios between 9:2 and 2:3
2. In green, a full frame sensor optimally cropped to maximise the area obtainable with a given aspect ratio
3. In red/yellow, an APSC sensor cropped in the same way as the full frame sensor

There is always a benefit to being able to choose a custom crop - in some cases significant. This is particularly the case for a square crop (64% more pixels than the APSC crop; 28% wider/higher), but even in the panoramic crop you end up with a significantly wider image (17%). For the square crop, the optimised crop is only 25% narrower than full frame (2/3 the pixels) of full frame.

Perhaps it's not earth shattering, but for something that is just software it seems a shame to pass it up...

I have bigger versions of the animation available, but these are the biggest I can upload to this website.

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Yes, and some lenses will even perform better, so you would have more coverage than expected. In the same way, some FF lenses can cover digital MF formats.

6 hours ago, jaapv said:

Very nice and clear. It would help if we knew the actual coverage circle of the lens, which can be considerably larger and switch off the automatic crop in the camera. 

Yes, it is unfortunate that the SL crops automatically to APS-C when you mount a TL lens. I understand there will be more vignetting if you want to use FF, but if you like square formats a TL lens is almost equal to a FF lens (only 25% less pixels).

Also, I would like to decide for myself what is good enough for me when using a TL lens on a FF sensor.
So where a square crop on my 24MP SL results in 16MP with FF lenses,  any TL lens will cover 12MP square, and possible something between 12 and 16 MP.

[KitW]

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You could also argue that vignetting is reduced with decreasing aperture,  so you could widen your image as you stop down. But at some point you would be making rhe process of photography more complicated. It's nice to pick up a lens and know you have a particular field of view, rather than having to think 'this will do the trick, but only if I use f5.6'.

At least if you are using the existing image circle, you should be guaranteed quality images. I am curious though, as to how much more you might reasonably get.