long exposure strange colours issue...from viewfinder

mikep

i first noticed this issue when trying some very long exposures - 30 minutes or so - and i figured that it was due to the sensor getting warm or something. so i just figured to reduce the exposure time. the following picture is a 30 minute exposure with the lens cap on, just so its clear, two reddish bands running across the image :



i went out today and tried some shots with a 10 stop filter, but to my surprise the very first shots i took at a mere 30 seconds, produced the same issue. this is today at 30 seconds :



oh no! i thought, and dropped to 10 seconds, and for the rest of the day, it was hit and miss. sometimes my 10 second exposures had no strange colors, and sometimes they did have them, it seemed to be quite random. sometimes it is there, and sometimes it is not so i am guessing that perhaps it is not related to heat?

10 seconds today :



just 5 minutes after taking the above picture, i took another few 10 second exposures with no problems at all. for comparison, this is a normal shot so you can see that the boat is not red at all in real life :



its annoying to buy the equipment for long exposures, then find out you cant take them half the time ;D

anyone seen this, got any ideas?

aquarian_light

Were these all with the same lens? take a 10 minute exposure with just the body cap to eliminate any artifacts from the lens. an exposure that long, if there are any light leaks it will just get exaserbated by the long exposure. Because that's almost what it looks like is a light leak from the lens, possibly at the mount. So to test this theory, take some with just the body cap, take some with a different lens, take some in a pitch black room. Becuase it looks like an over exposure just on those bands with a gamma tint.

aquarian_light

Were these all with the same lens? take a 10 minute exposure with just the body cap to eliminate any artifacts from the lens. an exposure that long, if there are any light leaks it will just get exaserbated by the long exposure. Because that's almost what it looks like is a light leak from the lens, possibly at the mount. So to test this theory, take some with just the body cap, take some with a different lens, take some in a pitch black room. Becuase it looks like an over exposure just on those bands with a gamma tint.

mikep

the first time i noticed was with the 70-200, on very long (30 minute and 15 minute) exposures

todays were with a 24mm, at 10 - 30 seconds

so different lenses have seen the exact same pattern of colour

Ironheart

@mikep what camera? Are you covering the viewfinder?

mikep

d700, i never thought of that though, might be the viewfinder leaking light in

but its odd how two pictures, 5 minutes apart, same setup, one has it, and one doesnt. maybe one i was stood in the sun and one i was stood in the shade, might have made a difference ....

testing with body cap on now

ill do one with the camera lying on its back, and one with the viewfinder pointing at the light

proudgeek

I encountered a similar situation (although not the sort of color cast you're seeing) when I first purchased by 10 stop ND filter. I couldn't figure out why all my images were so underexposed. The answer was that light was coming in through the viewfinder and essentially "bypassing" the lens so my shutter speeds were far faster than I was expecting. It wasn't until I started covering the viewfinder that I started getting "true" shutter speeds.

mikep

problem solved!

it was just me being dumb

its light leak from the viewfinder. just didnt occur to me as it was making such odd colours, and such uniform patterns.

one time that lovely purple colour made one of my pictures of a sunset look nicer actually maybe its a "tool" to be used at the appropriate time?

anyways, here is two 30 minute exposures with the body cap on. the top with the viewfinder under the light, and the bottom with the viewfinder blocked

aquarian_light

huzzah! I love being right lol
I knew that looked like a light leak. that's why they have that shutter than can close off the viewfinder. At least on the models that have that it's a very valuable tool!

John

Wow, this question was answered quickly.
It is indeed a good example of light entering through the viewfinder.
For camera's with a viewfinder shutter it's best to use that.
For camera's without one you can just use a piece of thick black cloth to cover the viewfinder. That works just as well. Or, when you only need a second or two exposure time, you can just keep your eye in front of the viewfinder. That should provide adequate shielding. (You can also use this trick with longer exposure times but that might get boring really quickly.)

chakoo

Sometimes even with viewfinder cover, I saw light leak when sun is at back of the camera. Then I use a black cloth to cover the viewfinder completely or I stand between sun and camera viewfinder.

Rx4Photo

A small strip of gaffer tape works wonders here. Keep a couple of small strips on one leg of your tripod for emergency use.

Golf007sd

@mikep: Glad it as a quick fix.

Question: the whole concept of taking a shot that is 30 minutes long still puzzles me. For what reason would you have the shutter open for such a long exposer?

I also hope you have a few spare batteries with you. A 30 minute exposure then followed by a 10 or 15 minute will surly cut in to your shooting adventure. :P

John

@mikep: Glad it as a quick fix.

Question: the whole concept of taking a shot that is 30 minutes long still puzzles me. For what reason would you have the shutter open for such a long exposer?

I also hope you have a few spare batteries with you. A 30 minute exposure then followed by a 10 or 15 minute will surly cut in to your shooting adventure. :P

Perhaps I can answer that question.
Long exposures turns moving water into a soft texture.
It's most often used for waterfalls and rivers but works wonders on costal regions and harbors as well.

Yes, it eats up batteries and yes, it's best to turn long exposure noice reduction on but if you know what you're doing the results can be very nice.

Ironheart

Yes, but isn't 1 or 2 or 5 minutes sufficient? 30 seems a bit long.

PB_PM

I agree, it shouldn't take more than 2-5 seconds to get smooth water.

Golf007sd

@John: thanks for the response. However, I have found that an ND filter will acomplish the same objective far more efficantly in much, much shorter time frame. It is one of the key usage of an ND filter.

spraynpray

30s works for me on a river so waterfall shots could be even quicker - this is only 6 seconds:

mikep

i was just experimenting with some slow moving clouds going across a sunset

it was interesting to see the path that the clouds took over a 30 minute period, although the noise was too much for it to be useable. it was a nice picture actually, enhanced by the lovely purple from the light leak

spraynpray

Hands up all those who use the little rubber viewfinder cover that comes in the box with the body?

proudgeek

You mean the one I threw out because I never thought I'd need it?

mikep

i dont even remember such a thing

Ironheart

@mikep, the D700 has an eyepiece shutter. On page 6 in the manual the control lever is specified as control #3.
On page 205 Nikon recommends using the shutter whenever your eye is not behind the viewfinder.

Beso

Question: the whole concept of taking a shot that is 30 minutes long still puzzles me. For what reason would you have the shutter open for such a long exposer?

I also hope you have a few spare batteries with you. A 30 minute exposure then followed by a 10 or 15 minute will surly cut in to your shooting adventure. :P

In addition smoothing water, creating different textures, etc., some use a long exposure to shoot star trails. Light leakage would probably not be as much of a concern shooting in a dark environment but very little light leakage over a 30 minute exposure adds up.

natascha

Hi All,
Just new to SLR - I've a Nikon D7100 and just wanted to say thanks for this info. It's been driving me nuts. I've been having the same problem with exposures over 20sec on beach scenes. Can't wait to try again. Thanks - cheers Natascha.

Paperman

So we have found the cause .... The question is, is it normal ?

I thought we covered/closed the viewfinder because the light entering from behind might fool the exposure meter. Not because light might enter & fall on the sensor ruining the image....