Help! Strange effect when using a '10 stop'!

foodpoison

foodpoison

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Name
Sean
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Here's the first image:

3785208093_fac47a75ae_o.jpg


Exif:
f/18 | 20 seconds | ISO100 | 10mm

Here are the other 2, and a weird thing is happening...

3785208323_d7142b8019_o.jpg


Exif:
f/22 | 160 seconds | ISO100 | 10mm

3786016398_7126d91602_o.jpg


Exif:
f/18 | 160 seconds | ISO100 | 10mm

Notice on the last 2 the slight change in colour? I'm pretty sure it's not my camera but I will check.

Started happening with my '10 stop welding glass filter'
 
Strange, have you tried the filter up the other way and seeing if the top 3rd is exposed differently?, I haven't noticed anything like that with mine.
 
not too sure about your problem but i do see a few dust spots in the clouds in #2, straight up from the highest tree in the middle, as well as the left side and extreme right.
 
Did you get some light leak? I can see a white haze gradually get worse in the middle of the last two. :shrug:
 
That's strange, I got exactly the same sort of problem when I tried welding sills on to my car using a Hoya ND4 :LOL:
 
Moved to equipment from landscapes as it is about the filter not the picture content.
 
ahaa I saw the haze but thought you were on about bins mysteriously going AWOL or something!

There seems to be a definite line across the grass where it starts.. weird.
 
ND10 type filters (welding glass) does give a colour shift, if the camera was set to AWB maybe it was having difficulties ?
 
im assuming it is the purple in the trees? all the colours are slightly different, could it be your white balance? over correctedon one of the sliders? as for the vignetting i would guess it was because it is at 10mm, and looking through more glass at the edges:shrug:
 
I recall very hazily somethng from college many years ago that when using colour film for long exposures you can get colour shift and that this can be accentuated when using filters. Bearing in mind the welding glass isn't the same thing as a specific filter, could it just be that its the properties of it that are confusing the cameras system and causing it over longer and longer exposures? :shrug:
 
It's definitely light leakage!
I struggled with the same problem and was getting a reflection of my lens onto the back of the filter which appeared as a magenta cast, because the camera's white balance has compensated for the green cast to the filter by adding a bucket load of magenta....I'm guessing it's just reflecting the convex shape at the centre of of your lens.
 
Maybe it is because the welding glass is a cheap piece of glass rather than a camera specific filter,dunno......:shrug:
 
I got a little bit of light leak on my trial last night FP. I was using a dish cloth pegged around the gap, and it slipped :LOL:. I'm going to find a pair of Chris thick black socks tonight and butcher them. Cut the toe off and slide in onto the lens barrel before attaching the filter holder. Then it should simply be a case of slipping it over the gap once in position. Oh and of course, I'm going to utilise that bit of rubber on the camera strap to cover the viewfinder to.
 
did you cover the viewfinder?
 
Could be a lot of things. White balance is one - don't use AWB, lock it to daylight or whatever or it is liable to shift. Light leakage is another, either from around the filter, or through the viewfinder (my guess here). Or both.

How are you calculating the exposure? How are you timing it?

I assume you are shooting digital, and not film with your AE-1?

Edit: crossed post with OP. Yes, light coming through the viewfinder which leaks around the piggy-back mirror, can affect parts of the image, depending on the angle. You must cover the viewfinder.
 
Not using AWB, I'm setting my own custom white balance based on images I've taken with no white balance alterations. I doubt the light leakage is coming in through the filter since it is sealed completely by blu-tac. If it was through the viewfinder surely it would be a splodge in the centre of the image?

Calculating the exposure by taking a control image with no filter, and then adding the filter and taking the shutter speed down by 13 stops (roughly the density of the filter). I'm using a 3rd party version of the Canon TC-80N3 to time the exposure in minutes and seconds - very accurate.

Shooting digital with my 40d - exif data probably isn't intact as I'm saving a copy of the original JPEG.
 
Just had a thought, it could be light entering the edge of the glass and penetrating down through it, if the sun was directly above you it could have travelled through the edge so far down lightening the upper part of the filter, just a thought :shrug:
 
Ajophotog said:
Just had a thought, it could be light entering the edge of the glass and penetrating down through it, if the sun was directly above you it could have travelled through the edge so far down lightening the upper part of the filter, just a thought :shrug:
Click to expand...

Not a bad thought either (y) Maybe. All sorts of strange things can happen with a long exposure like that in bright sun.

On the light entering the viewfinder, just take a 30 seconds exposure with the viewfinder exposed to a bright sky. Or with a torch shining through it.

With my 40D, I get a rather nice looking sunset effect, brighter in the centre and starting with blue streaks then fading to red orange, with a yellow bit on one side. Bottom third of the frame is black, but the coloured bits are very bright.

Edit: Just tried it on my 350D and it produces a grey all over fog, with bright streaks at each end.
 
Foodpoison - did you close the view finder? If not, you will eventually see a colour cast start to emerge in all sorts of ways, unatural / uneven. Light leaks massively through the view finder on super long exposures, especially during the day.

Gary.
 
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