thescatteredimage 6:06am, 8 November 2009
Hello. Just started having a crack at digital IR. I'm using a Canon 5D mark ii, Zuiko 28mm/2.8 and Hoya R72. Im only using the olympus lens because the filter I have doesn't fit on any of my Canon lenses. Hoping to get an IR filter to fit a few more lenses soon.

Exposure time is 30sec, aperture f8 or f11. I tried with bigger apertures down to f2.8 and there was no real difference.

The colour cast around the edges is of course blueish before swapping the red and blue channels.

Does anyone know what the problem here is? Anyone know how to fix it?
notrub1943 8 years ago
Unfortunately, this particular lens appears to have a pronounced "hotspot." Run a search on this forum's threads for this phenomenon; it's fairly common. You can experiment with different lenses to possibly minimize or eliminate the "hotspot." Good luck.
thescatteredimage 8 years ago
Hmmm ... I thought it seemed rather large for a hotspot. Also, the colours seem correct in the spot in the middle, but way too pink on the outside. Anyway, I'll take that on board, maybe this lens isn't any good for this application.
vintod 8 years ago
The size of the hotspot depends on the aperture. At what settings was this shot taken?
paneraica 8 years ago
Hot spot can be small and dense or large and light as in your images.

I posted a few posts down asking the same questions, so might be worth checking out.

Trying to avoid them also

thescatteredimage 8 years ago
vintod .... that's what I assumed, but as I mentioned in the original post, changing the aperture down to f2.8 made no discernible difference ... meaning that there's a similar pattern at f11 and f2.8.

paneraica ... yeah. Checked out that thread too, thanks. Probably will just get another filter and try a different lens.

thescatteredimage 8 years ago
Problem sorted ... lens issue.

Canon 5D mark ii + Zuiko 28mm/f2.8 + Hoya R72 = not great for IR for the reasons outlined in this thread.

Thanks peoples.
vintod 8 years ago
What I came to notice was that with an aperture like 2.8 the hotspot will be large but it will have softer edges. An aperture like f/11 would give me smaller hotspots but I would have more of a solid line at the edge (for me this was easier to fix in post or hide in the composition).

I suppose either (hard edges or soft edges) can be fixed in post processing with some PS magic, but the best bet is probably just to grab a different lens; google around for a while and you will find several lists of lenses that do not hotspot to this extent.

From what I've read, if a lens is going to hotspot, there's really not much you can do to stop it. If swapping out lenses is not an option, then just keep trying different hoods, always stay away from the light source, use faster shutter speeds, clean out any dust, and remove any other unnecessary glass from the front of the lens to minimize it as best as you can.
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