FujiSigmaNolta
old hand
Reged: 21/06/2005
Posts: 1160
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Hi all,
I didn't know where to post this, but I was trying out one of my Sigma SD10s which I removed the hot mirror from. I went out today to take some IR photos and this camera is great for that, it can even focus through the filter and all. Now the question is, should I take a meter reading before the filter or with the filter on? I did it without first and I was getting massive over exposure, then I put it about 3-5 stops down and the results looked OK on the camera screen as I could see detail and it looked like they would come out alright, but when I ran it through the software they were very underexposed and had lots of noise. So I had to resort to using 3rd party NR software (which being a purist, I hate doing) and resizing to hide introduced softness (ditto). I also had the WB mistakenly set at "Incandescent". Would this would have contributed to the added noise? Any help/suggestions appreciated.
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Regards,
FujiSigmaNolta
My Flickr mess
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 3752
Loc: Really Here In Name Only
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The meter is balanced for visible light with an average colour temperature (daylight) and will almost certainly misread when the visible light is removed with a "black" IR filter. I think you're going to have to bracket, it would make most sense to meter without the filter & work from that, I'd suggest trying -1 -2 -3 stops find out which one looks best & refine from there.
Softness - have you remembered to correct the focus by using the distance scale visible & IR indices? It may help to stop right down but getting the right focus in the first place is surely the key.
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FujiSigmaNolta
old hand
Reged: 21/06/2005
Posts: 1160
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Quote:
The meter is balanced for visible light with an average colour temperature (daylight) and will almost certainly misread when the visible light is removed with a "black" IR filter. I think you're going to have to bracket, it would make most sense to meter without the filter & work from that, I'd suggest trying -1 -2 -3 stops find out which one looks best & refine from
I have done so, but it seems that I on average underexposed for about 5 stops, just looking at the pics now. The Sigma does have an issue though, when you use the wrong white balance. Even in normal photography it is imperative that you use the right white balance settings.Correction is difficult if you don't and can lead to increased noise at times, which I think it may have been one of the contributing factors.
Quote:
Softness - have you remembered to correct the focus by using the distance scale visible & IR indices? It may help to stop right down but getting the right focus in the first place is surely the key.
The lenses I used apart from one did not have the IR index scale but the Sigma SD10 without the hotmirror does a great job autofocussing through the IR filter I have to say,the softness was introduced because of the excess noise and the subsequent use of Noise Reduction software. I have a few that survived and here's one:
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Regards,
FujiSigmaNolta
My Flickr mess
My Blog
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