I’ve been learning about photography. I’m totally unsuccessful from an artistic point of view but I’m finding the mechanical aspects really interesting. Mostly as a result of this amazing free online course (warning, I found the course quite maths heavy, and I did a PhD that focused on maths)
Since I started looking more carefully at photos, I’ve felt like the pictures I put on Instagram looked different there. Light something had changed in the contrast or similar. I wanted to do a quick experiment to find out if it was my eyes playing tricks or indeed some interesting optical illusion.
So I found a handy wikipedia page and took a screenshot of it.
I then converted that screenshot (which was png on a mac) to jpeg so it could be put on Instagram:
It was posted (it’s since been deleted because it’s very uninteresting to my followers) and I took a screenshot of the image on both my phone and on my mac. PS: fairly obviously, I didn’t use a filter or adjust anything)
I lined up all the pictures and took one large screenshot:
…then used Darktable’s color picking tool to check each colour (using area rather than spot measurement:
…and it turns out it isn’t an optical trick: the colours do come up differently when tested:
The order of samples is:
- Screenshot png
- Screenshot jpeg
- Instagram on desktop
- Instagram on phone
…and clearly the ones that Instagram does are different from the ones that aren’t. So what is going on?
- I don’t think that noise is making a difference (I do think that inprecision in my measurements is causing the tiny differences between the jpeg and png versions).
- I don’t think it’s the monitor making the difference – the test could have been done entirely without looking at the monitor so that’s out.
- I don’t think it’s something about firefox – because that wouldn’t explain why the iPhone screenshot is different by the same amount.
- It’s not a darkroom import artifact – all the colors were on the same image screenshot before darkroom got involved.