Depth of field


Time for an update: I still use film, though. Not vast quantities, but I have a darkroom, and I'm not afraid to use it.

I enjoy every image I take: I hope you'll enjoy looking at them.
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Depth of field

4 Nov 2020 10:34AM   Views : 490 Unique : 340


And my mind’s been working hard since I wrote yesterday’s blog. The words keep on whirling round my head, like the introduction to my least favourite school book, Clement V Durrell’s 'O' Level Algebra tome… My maths teacher thought Durrell was wonderful: I… looked for a more helpful text.


Anyway, the pragmatist in me took two cameras out for my morning walk, intent on a real-life comparison. And my findings are that it’s not the biggest deal ever, but there’s just a little less depth of field with a bigger sensor, all other things being equal.


My comparison was between an Olympus OM-D EM-1 with a 45mm f/1.8 Olympus lens and a Sony Alpha 7R III with a Sony 85mm f/1.8 lens. I shot as near identical frames as I could with the two cameras, at a variety of apertures. Some of the results are here.


My conclusion is that the good Professor is making a point about close-up and macro pictures, rather than photographs in general. And I need to tease it out a bit more. But given my relationship with algebra, I shall leave most of the maths to other people…


From the top: Sony, f/1.8; Olympus f/1.8; Sony f/5.6; Olympus f/5.6; Sony f/22; Olympus f/22.


Take care out there!

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dudler Avatar
dudler Plus
20 2.1k 2048 England
4 Nov 2020 10:35AM
Not convinced? Go on - try it yourself. You may learn something interesting and useful about how your own lenses work...
James124 Avatar
James124 Plus
8 81 59 Portugal
4 Nov 2020 10:55AM
Another difference is the Olympus lens/sesnsor combination is just a touch warmer than the Sony.
AltImages Avatar
AltImages 3 4
4 Nov 2020 11:07AM

Quote:Not convinced? Go on - try it yourself. You may learn something interesting and useful about how your own lenses work...

Yes. That's the important bit. People can produce technically better images than Cartier-Bresson, Weston etc with their phones. But the best photos come from the photographer's brain not the camera. That's where the Professor was correct in his article, when he said what's inside the camera doesn't matter!
dudler Avatar
dudler Plus
20 2.1k 2048 England
4 Nov 2020 11:39AM
Quite what the differences between the sensors are is not so clear: apart from the f/5.6 shot, I'd left the Olympus on something other than daylight, and therefore had to correct in the RAW conversion. The Sony images are as shot.

Overall, I feel that the Sony gives me colours I like better than the Olympus, and WB is more predictable, but this is all very personal, and correctable in camera or in editing.

The search, as Paul suggests, is for a way to channel brain-stuff through the camera...
dark_lord Avatar
dark_lord Plus
19 3.0k 836 England
4 Nov 2020 12:47PM
A very interesting comparison John, and exactly right as the framing and content are identical. The difference is most visible in the background detail.
That, for photographers in practical and results terms is what's important.

Looking at this from a different angle, and it's likely the maths will bear it out (my brain shuts down when maths are involved), the images would look identical (colour resonse aside) if the aperture in both cases was the same (I'm talking physical size in mm). Essentially meaning a higher f number is needed on the larger sensor for the same 'look'.

I reckon a very similar principle would apply to a comparison with full frme and medium format.
dudler Avatar
dudler Plus
20 2.1k 2048 England
4 Nov 2020 2:02PM
I THINK that what the good Professor was saying may be that if the 'size of the hole' is the same, and the angle of view is the same... Still working on it. Happy to email a scan if you want.

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