Yellows and Reds


Lubbyman

Link Posted 03/07/2019 - 11:01
There was mention in a Your Photos thread about how difficult it can be to photograph yellow or red subjects. So, two questions:
1. (The techie one) Why are yellow and reds such a problem for sensors?
2. (The practical one) How do you deal with yellows and reds?

I'm currently struggling with a rather attractive bright red flower and failing miserably...

Steve

Algernon

Link Posted 03/07/2019 - 12:01
It's probably due to brighter shades of red and yellow being out of gamut on monitor displays. Underexposing and bringing back in the edit may help. Certain lenses are also known to handle these colours better for flowers etc.

One such lens is the Pentax-A 35-105 see ....

Evening walk with the Botanical Lens

https://www.dpreview.com/forums/thread/4403730

He also has a flickr page...
https://www.flickr.com/photos/alex_virt/albums/72157699614530184

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Last Edited by Algernon on 03/07/2019 - 12:27

Lubbyman

Link Posted 04/07/2019 - 09:43
Thanks Algi, you might be onto something.

Being out of gamut hadn't crossed my mind. I use sRGB for everything, mainly because it's supported (even if not perfectly) by every screen in the house. The K3 is set to use sRGB colour space. Now, out of gamut colours must be recorded as something, but what? If they are recorded as the nearest sRGB colour, or even spread across a narrow range of sRGB, that would certainly result in loss of detail. Some experimenting with K3 set to AdobeRGB seems to be on the horizon - but what experiments when you don't have an AdobeRGB screen? Life is full of questions...

That dpreview thread is interesting. "Decreasing brightness increases saturation of all colours except yellow which gets more saturated as brightness increases." ties in with my experience. Then the perfect punchline: "There is a scientific explanation of this phenomenon, but I can't remember it".

Thanks again.

Steve

johnriley

Link Posted 04/07/2019 - 12:06
If you start to use AdobeRGB then you may well find your images somewhat dull when posted on the web, so I'd stick to the universal sRGB.

There are a few ways around your flower problem. The first is lighting. The best natural light is bright overcast, but definitely not full sun. So give yourself a fighting chance and keep the lighting even.

Second, use Natural if shooting in JPEG. The Bright setting that comes as default on Pentax cameras is a bit too severe.

Third, watch you don't over-expose the image. I routinely apply -0.3 EV exposure compensation. If you over expose, red is probably the first colour that will become clipped and just solid, detail-free red.

Hope that helps!
Best regards, John

pschlute

Link Posted 04/07/2019 - 12:49
Adding to what John has written using a AdobeRGB image to post to the web is not a good idea.

There can be an advantage in starting off with a AdobeRGB image (or a wider gamut ProPhoto image), doing all your editing in that wide colour space and then converting the profile to sRGB before saving. This is because the wider gamut colour space is going to show less artefacts after an edit than a narrow one. But if you are going to go down that route you need to use a wide gamut monitor so you can see what your colours are doing during the editing process.
Peter



My Flickr page
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