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05-14-2010, 06:40 AM   #16
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QuoteOriginally posted by adwb Quote
OK found it on page 60 through 63 , as you correctly said he talks about the effect that different apertures have on certain colours. essentially all he is saying is that if you over or underexpose a image there will be shift in the hue of a colour which is obvious.What he is however pointing out is that this affect some colours more than others yellow being a good example as it will go from a shade of yellow to a ochre if underexposed enough while other colours may not have such a severe reaction.
As this is a book on how to try to get the best exposure with out resorting to hours of PP it a valid point to make , as compensation for a given light situation may rectify the overall exposure but can have side effects.
There are some images to demonstrate this and if they certainly do show how you need to be aware of this phenomenon.
General under exposing darkens and allows recovery later when very often over exposure is not as recoverable.
take three images one 2 stops under; one normal ;and one 2 stops over , you will get the two stops under back to normal most times but often won't with the 2 stops over, IMHO.

Alistair
Well that is saying that EXPOSURE (by way of adjusting the f/stop) affects the colors. I'm sure you could get this affect by keeping the aperture constant and adjusting the shutter speed. Basically, the amount of light hitting the sensor (or film) is what's affecting the colors, and NOT the aperture.

I (and perhaps others?) were assuming that the exposure was kept constant, and adjusting the aperture (and the shutter speed to keep the exposure constant) was the "direct" cause of the color differences.

I don't have the book, I was just taken aback by the OP's "revelation" that f/stop can affect colors. It appears he was wrong, and that EXPOSURE affects colors (which is pretty much common knowledge)

05-15-2010, 07:36 PM   #17
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QuoteOriginally posted by egordon99 Quote
Well that is saying that EXPOSURE (by way of adjusting the f/stop) affects the colors.
I totally agree. I'm not that experienced with DSLR (just above 2000 shots) but what egordon said makes a lot of sense. If you're shooting at f22 100 iso and x time, you'll have the same colours as f2, 100 iso and x=compensation of f22 to f2.
(is that clear enough?). So, the same amount of light (what egordon said) is hitting the sensor.

But: look at a yellow wall in a dark room and the same in a very bright room. Even if the eye adjusts the way we percept colours in a magnificent way, it is still changing. We can go from [: oker] - egg yellow (some orange) to a bright yellow colour.
So the point is over or under exposing "a certain colour"(again: even if overall exposure is correct).
Take a black/white scene or snowscape. Spot metering (all auto settings -> so said correct exposure) on the black or the white will give different colours for black and white. As for snow, you better over-expose.
So if you use scene metering (sorry, it's late ^^), so the complete image, for white people, they will look too white, so better under expose. For black people, they will look too dark. Sabatella explained it also.. Please, don't make jokes about yellow people
Of course, if your background changes, you may have to reverse the process:
if you have a bright background and a louisanian bluesman (black skin of course), you'll probably have to under-expose with segment metering (ah! found my vocabulary again). Otherwise, he'll look a bit grey, especially if you're shooting B&W.

I think, to resume, that colours changein function of the f-stop if overall exposure changes. And in some cases, even with segment metering, the exposure will change.
I noticed this in low light concert conditions. Corrected under-exposed shots don't give the same correct-exposed shot's colours (there were red and yellow ( who said yellow? ) spotlights.
But I think I'll have a look at those books! One never stops learning.
If you can't learn no more, it is because you're too old to learn.
(some 'translation' of a japanese saying)
NB: sorry, this post may be long, but have some difficulties with explaining sometimes ^^

Last edited by ezechiel; 05-15-2010 at 07:43 PM.
05-16-2010, 06:30 AM   #18
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Books...

These books contain so much information, how the heck can one remember it all.??My head is swimming...

I can just picture the scenario....please wait five minutes before I take your photo whilst I try to remember everything I read in the book and fiddle with my multi knobbed /switched/buttoned dslr......

Oh yeah....and ten different lenses..

and one hundred lighting conditions..
05-16-2010, 02:30 PM   #19
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QuoteOriginally posted by Daveinozbikes Quote
These books contain so much information, how the heck can one remember it all.??My head is swimming...

I can just picture the scenario....please wait five minutes before I take your photo whilst I try to remember everything I read in the book and fiddle with my multi knobbed /switched/buttoned dslr......

Oh yeah....and ten different lenses..

and one hundred lighting conditions..
That sounds like every time I try to take a portrait of my wife. I end up with a series of photos starting with technical flaws and great expressions, and finish with a technically perfect photo of the "stop taking photos of me or I will break that damn thing" expression. By the way, printing that last photo as a little joke may not be a good idea.

Practice does help, so instead, I use my dogs. They're just laying in the sun anyway.

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