Shodddy attempt at IR

acparsons · Jul 2, 2015

I attached an IR filter to my d300(not converted). Here is what I came up with after PP. I think that it's grainy due to the long exposures. Had a hard time focusing, 1. I focused manually before putting the filter on and 2. I used auto focus after the filter was on. Tips on focusing and PP would be great.

1

try by Machiavelliar, on Flickr

2

iui by Machiavelliar, on Flickr

3

fd by Machiavelliar, on Flickr

4

DSC_7031 by Machiavelliar, on Flickr

5

DSC_7003 by Machiavelliar, on Flickr

480sparky · Jul 3, 2015

Do not use AF or change focus after you put the filter on.

wfooshee · Jul 4, 2015

Did you have to boost these any in post? That will exaggerate any noise.

Noise is the least of the issues, though. I'm not sure your filter is any good. All of the images have a bright area in the center, and on #4 there is an obvious reflection of the white object at the top of the building to your right. 1 and 2 seem focuses OK, but the others are not. I don't know how to use an IR filter, though, I'm not sure what the focus compensation would be.

Back in the film days, shooting IR film, you'd focus in the viewfinder, then look on the lens's distance scale and move the focused distance over to the red dot (or line on a zoom lens) to compensate for the fact that IR light focuses differently than visible light.

acparsons · Jul 4, 2015

I had to tweak the colors and channels in post. I think might have over-sharpened a bit. I'm not sure if the white spot is a smudge on the filter or another issue. I'm thinking it's something to do with the camera sensor.

Here is one that I took with a D70s a couple of years ago, turned out better.

DSC_0935 by Machiavelliar, on Flickr

petrochemist · Jul 5, 2015

wfooshee said:
Did you have to boost these any in post? That will exaggerate any noise.

Noise is the least of the issues, though. I'm not sure your filter is any good. All of the images have a bright area in the center, and on #4 there is an obvious reflection of the white object at the top of the building to your right. 1 and 2 seem focuses OK, but the others are not. I don't know how to use an IR filter, though, I'm not sure what the focus compensation would be.

Back in the film days, shooting IR film, you'd focus in the viewfinder, then look on the lens's distance scale and move the focused distance over to the red dot (or line on a zoom lens) to compensate for the fact that IR light focuses differently than visible light.

The bright spot in the center is known as a 'hot spot' and is down to internal reflections in the lens. It's a very common problem in IR photography, so there are many lists of lenses that are free of hot spots, around on the net. Aperture can have a significant effect on hot spots, and it seems even the camera body can. I've had issues with hot spots using the kit zoom on an unmodified Micro 4/3 body yet non at all when using the same lens on a modified camera.

If you don't have live view, focusing is generally trial & error. Phase AF rarely detects IR wavelengths. Contrast AF uses the main sensor so should cope with the wavelength shift provided there's enough light for the AF to work.

Older lenses with IR focusing marks (as mentioned above) tend to be better wrt hot spots too.

I don't think the images are too shoddy for early experiments, if it wasn't for the hot spot no 4 would be really nice IMO.

acparsons · Jul 5, 2015

Great advice. Thanks.

Derrel · Jul 6, 2015

Bjorn Rorslett's Nikkor Lens Evaluations often mentions lenses that have particularly good, or poor, IR performance. That lens has a really pronounced IR hotspot...it's definitely leaving an impression on the IR images it makes...

Tailgunner · Jul 6, 2015

480sparky said:
Do not use AF or change focus after you put the filter on.

This^

Set up the focus first w/o the IR filter and then cut off the AF and install the IR filter. I can't help much more since I'm just now messing with IR myself. I will say that some filters are better than others as well as some bodies do better than others. It seems like older bodies are preferred vs newer models. Also, another issue with IR or long exposers is light leakage. It's better to use live view if possible and cover the view finder. I have seen some people wrap their lens up as well as cover their camera bodies. I know for me, covering the view finder was a big help. I would get all kinds of light leakage otherwise with it uncovered.