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04-08-2013, 02:25 AM   #1
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Purple Banding from Viewfinder

I have noticed that when I took long exposure pictures recently, some of them had purple bands on them- resulting in discolouration, differential exposure in specific places, and loss of contrast. The bands were always the same in all the pictures, so that meant that it wasn't flare or something else to do with light from the lens since that light is different depending on the photo. To find out more, I did some tests and to cut it short, I believe that the issue is caused by light entering the viewfinder and reflecting off the inside of the camera, and it only appears when the exposure is long enough, or the sensitivity is high enough for it to affect the photo.

The first image is of the effect (exaggerated somewhat)- 9 minute exposure at ISO 200 with the viewfinder exposed to an (admittedly not too bright) open window).

The second image was taken in exactly the same scenario, but with a piece of card covering the viewfinder.

As you can see, it can be quite an issue, and has ruined several photos when I haven't noticed it until too late (as it mainly happens in bright sunlight, the LCD screen upon which I view the image after taking does not have enough contrast to notice the effect, unless I look very carefully, which I don't). Just as some background, in general the pictures which show this effect are IR photos (hence the long exposure).

I post this because I am interested whether anyone else has had this issue, and particularly whether it is just my camera (a K-r), whether it is just the K-r, or whether all cameras do this to some extent, since I can find just about nothing elsewhere on the internet and this forum about this issue.

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Last edited by njleach.1; 04-08-2013 at 06:22 AM.
04-08-2013, 05:06 AM   #2
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Higher end cameras come with a plastic piece that fits in the viewfinder. This is usually the first thing that gets lost...

A piece of black electrical tape works just as well and is more convenient.
04-08-2013, 08:12 AM   #3
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Why, oh why, has Mr. Pentax never included a viewfinder blind? They have been around forever, and resolve an infinite number of exposure problems when the user's eye is not shading the eyepiece.
04-12-2013, 01:43 AM   #4
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Thanks for posting this, hope it will be useful to someone else.

The K10D and the K-5 both include a viewfinder blind. I suspect all cameras from the *ist to the K-5II have one, and perhaps/probably the range below too (K-r, K-x, K-30, etc.).
I never had this issue with the K10D, however the K-5 is prone to it (at least with daylight long exposures with a ND filter, I've had less issues with nighttime exposures). I had an 'ah-ah' moment when finding that it was due to the viewfinder.

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04-12-2013, 07:48 AM   #5
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QuoteOriginally posted by kokol Quote
Thanks for posting this, hope it will be useful to someone else.

The K10D and the K-5 both include a viewfinder blind. I suspect all cameras from the *ist to the K-5II have one, and perhaps/probably the range below too (K-r, K-x, K-30, etc.).
I never had this issue with the K10D, however the K-5 is prone to it (at least with daylight long exposures with a ND filter, I've had less issues with nighttime exposures). I had an 'ah-ah' moment when finding that it was due to the viewfinder.
When I said viewfinder blind, I was not referring to the easily lost and clumsy to use attachment blind, but a blind built into the viewfinder with a knob or lever or button to push. I apologize for not being more specific.
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