Photographically relevant optical illusion

[John Chardine]

I really enjoy NASA's Astronomy Image of the Day, here:

http://apod.nasa.gov/apod/ap121007.html

The post for today 7 October shows an optical illusion that must affect the way we look at images all the time, and therefore how we process our images, present them in print form and critique here at BPN. Perhaps I am overstating this?

[Ed Cordes]

John, you bring up a very valid point. I have often wondered if we really are objective in judging the colors on our monitors. Even when using calibrated equipment there seem to be a lot of other variables affecting my judgement. One example is that my eyes seem to "eat up" saturation. If I over saturate an image for a certain effect, my brain seems to get used to it and then other images seem rather dull in comparison. Sometimes I think my brain sees what it "wants to see" in colors. I apparently have a certain bias going into the image processing session that carries through the day. Then if I ask my wife to look at an image or I go back to it a day or so later I see it in a whole different light - so to speak!

So, what is real? With the variation in ambient light and outdoor color temperature I'll venture a guess that even if you were somehow able to bring the original scene into your processing room there would be huge variations in the perception of "the real" scene.

A few years ago I posted an image of a mom and colt zebra from the Ngorongoro Crater. The image was very early morning light (warm) and the animals were covered in the dry reddish dust of the crater (that year there was a drought). Many criticized the image as the white stripes of the zebra were not white but had a color cast. In my mind, there was not a color cast but a true representation of the dust and morning light on the white stripes and the general acceptance by some in the audience that zebra stripes should be white. if I processed the image for white stripes it would not have represented what my mind remembered of the scene. However, who is to say my mind remembered correctly???

[Don Railton]

All I can say John about that 'illusion' is WOW...! I would have put good money on the colours being different... does this mean we need to spend 10 minutes looking at a grey card before we start processing our images so our eyes can go through some sort of 'auto calibrating" process...?

DON

[Tom Graham]

Here is the image constructed as you watch, see the grey "change" before your eyes.
http://en.wikipedia.org/wiki/File:Op...reysquares.gif
At what point do A and B change for you? Wish it would animate slower, anyone know how to slow down the GIF? Or select GIF frames individually?
Tom

[Tom Graham]

GIF frames - a video editing program I use was able to separate the gif frames. (There are 25 total).
Here are 3 of them as the illusion progresses -


The "B" square "changes" slowly. As it becomes surrounded by dark squares.
You don't believe the "B" grey square is constant? Put it into PS, each of the three measure 120.

Tom

[Doug Brown]

Quite fascinating! Thanks for sharing!

[Jon Rista]

John, you bring up a very valid point. I have often wondered if we really are objective in judging the colors on our monitors. Even when using calibrated equipment there seem to be a lot of other variables affecting my judgement. One example is that my eyes seem to "eat up" saturation. If I over saturate an image for a certain effect, my brain seems to get used to it and then other images seem rather dull in comparison. Sometimes I think my brain sees what it "wants to see" in colors. I apparently have a certain bias going into the image processing session that carries through the day. Then if I ask my wife to look at an image or I go back to it a day or so later I see it in a whole different light - so to speak!

So, what is real? With the variation in ambient light and outdoor color temperature I'll venture a guess that even if you were somehow able to bring the original scene into your processing room there would be huge variations in the perception of "the real" scene.

A few years ago I posted an image of a mom and colt zebra from the Ngorongoro Crater. The image was very early morning light (warm) and the animals were covered in the dry reddish dust of the crater (that year there was a drought). Many criticized the image as the white stripes of the zebra were not white but had a color cast. In my mind, there was not a color cast but a true representation of the dust and morning light on the white stripes and the general acceptance by some in the audience that zebra stripes should be white. if I processed the image for white stripes it would not have represented what my mind remembered of the scene. However, who is to say my mind remembered correctly???

I think you've hit on something important. While your observers saw an "incorrect" color balance, they were also "out of context". The image of the checkerboard in shadow is a demonstration of the fact that color perception requires context. In the case of your Zebra, there was a certain context that conditioned the mind to understand why the color was correct. I think, as photographers, since we spend so much time with the visual side of things, we sometimes forget that there is often a need to include additional context, such as in the form of words, to help our viewers see the image correctly. I've often thought about including a small description card in prints that I frame, under the photo in its own space in the matting. Just to help put people in the right context, so they view the image with the right mindset and perspective.

I think including a short description of our works early on, as metadata when we are importing and organizing our digital libraries, it'll help us keep things in the right context as well, even long into the future.

[Tom Graham]

"...need to include additional context, such as in the form of words, to help our viewers see the image correctly..."
I think it depends on the purpose of the image.
If it is to instruct/inform/record, then yes explanatory text is helpful or required. (As in a scientific article).
If purpose of image is to present a moment in time evoking in the viewer emotion or questions, then the image needs no text.
If I feel that I can't make an image to fully represent the scene (e.g. much of wildlife), then I shoot video.
And BPN I think is about the second category, presenting a moment that the image itself communicates.
Tom