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12-23-2010, 09:42 AM   #1
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Red cast in high ISO - Solution found!

Hi all,

Can all k5 user test it out for me whether you guys also having the same problem that I am facing now?

This red color cast only appear when using high ISO, for an example, 12800 above. sometimes has, sometimes not.... Please try until ISO51200.

This red color cast sometimes at upper part of the photo, sometimes bottom part.

p/s: photos from ISO80~ISO6400 are all perfect. No flash in this photo.

Regards,

Tom

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Last edited by kamayok3; 12-23-2010 at 10:52 AM.
12-23-2010, 10:02 AM   #2
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Compact flouescent bulbs cause this. Very common, and it happens with all camera makes.

The shutter speed is high enogh you are catching the colour flicker of the light source.

Slow the shutter to under 1/60, or use a flash and this will go away.

Nothing is wrong with your camera, and it is not a problem of high ISO.

Or change your light bulbs back to tungsten filiment...
12-23-2010, 10:06 AM   #3
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QuoteOriginally posted by KungPOW Quote
Compact flouescent bulbs cause this. Very common, and it happens with all camera makes.

The shutter speed is high enogh you are catching the colour flicker of the light source.

Slow the shutter to under 1/60, or use a flash and this will go away.

Nothing is wrong with your camera, and it is not a problem of high ISO.

Or change your light bulbs back to tungsten filiment...
Is it? Just because of the shutter speed or not using flash causing it?

Hmmmm........ will try it again then.

Regards,

Tom
12-23-2010, 10:10 AM   #4
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Yes.

I'm not making this up. There are plenty of other posts with this question. It is not the first time I have seen this either. Usually the photo is a high ISO test shot of a cat in a kitchen.

Try a series of test shots, start at 1/1000, and work down to 1/20, and you will see the worst colour shift when the shutter speed matches the light source flicker frequency.

https://www.pentaxforums.com/forums/pentax-video-forum/114684-k-7-vertical-ba...ite-video.html
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/93553-inconsist...alance-k7.html
https://www.pentaxforums.com/forums/pentax-dslr-discussion/84163-yellow-streaking.html

Also white LED lights:

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/124514-strange-...id-happen.html
https://www.pentaxforums.com/forums/pentax-dslr-discussion/93809-modern-led-s...-problems.html


Last edited by KungPOW; 12-23-2010 at 10:21 AM.
12-23-2010, 10:14 AM   #5
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Okay...Thanks for the great advice. So, I am in P mode. So, what is the best mode should I use when shooting in extreme high ISO? Any recommendation?

Regards,

Tom
12-23-2010, 10:22 AM   #6
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It wouldn't surprise me at all if there is some imaging deficiencies in the extended ISO range. That is why, by default, extended ISO is turned off.
That way, you can make the choice of not shooting at these very high ISOs or you can choose to accept that the imaging is less than perfect.
As others have said, if you are shooting under florescent lights, you need to be shooting around 1/25 of a second to avoid colour banding off the lights.
Your image is also underexposed, BTW.
12-23-2010, 10:28 AM   #7
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QuoteOriginally posted by Wheatfield Quote
It wouldn't surprise me at all if there is some imaging deficiencies in the extended ISO range. That is why, by default, extended ISO is turned off.
That way, you can make the choice of not shooting at these very high ISOs or you can choose to accept that the imaging is less than perfect.
As others have said, if you are shooting under florescent lights, you need to be shooting around 1/25 of a second to avoid colour banding off the lights.
Your image is also underexposed, BTW.
Thank you for the explanation. Maybe this is the first time I am using a semi pro DSLR. Will do all the testing more and see the result.

Regards,

Tom
12-23-2010, 10:35 AM   #8
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Good point on the underexposure.

At high ISO's, you will get better results by over exposing, and then pulling the exposure back in post process then you will by underexposing and trying to push the exposure up.

The technique is called "expose to the right". Watch you histogram so that you don't blow out highlights.

Expose Right

Also remember that at extreme conditions, things like the exposure meter on the camera will not be as acurate as in normal light conditions. Again, this happens with all camera makes.

As for what mode to shoot with, it really makes no difference. If you wanted to try the shutter speed experiment, you need to control shutter speed, so either use AV, M modes. Change you custom options to allow 1/3 stop steps.

12-23-2010, 10:40 AM   #9
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QuoteOriginally posted by KungPOW Quote
Good point on the underexposure.

At high ISO's, you will get better results by over exposing, and then pulling the exposure back in post process then you will by underexposing and trying to push the exposure up.

The technique is called "expose to the right". Watch you histogram so that you don't blow out highlights.

Expose Right

Also remember that at extreme conditions, things like the exposure meter on the camera will not be as acurate as in normal light conditions. Again, this happens with all camera makes.

As for what mode to shoot with, it really makes no difference. If you wanted to try the shutter speed experiment, you need to control shutter speed, so either use AV, M modes. Change you custom options to allow 1/3 stop steps.
Okay. Understood now. Nothing wrong with the K5 unit then. Thanks and Merry Christmas to all of you.

Tom
12-23-2010, 11:38 AM   #10
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QuoteOriginally posted by kamayok3 Quote
Is it? Just because of the shutter speed or not using flash causing it?

Hmmmm........ will try it again then.

Regards,

Tom
It's shutter speed. Use 1/30th or slower and it will not occur.
12-23-2010, 06:15 PM   #11
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Thanks guys. Will always remember.

Tom
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