The danger of hot spots with infra red photography

[DPNow]

*Choose your lens for near infra red photography with care* I have long been interested in infra-red photography and have even used infra-red film...

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[Patrick]

Re: The danger of hot spots with infra red photography

*Choose your lens for near infra red photography with care* I have long been interested in infra-red photography and have even used infra-red film...

Click to read the whole article...

I experienced this when I had the Canon 10D converted some years ago (I think you will find I posted something to this effect then) I had a problem with just one lens, the Sigma EX f2.8 10-20. Which I considered a shame as the wide angle & infra red combination looks particularly good.
I had the hot pot, plus it would not give sharp images, I thought the camera to be at fault, had the focusing re-calibrated for IR but it didn't sort the problem. The Sigma EX 17-35 was spot on, so I drew the conclusion that it was super wide angle lenses were the issue, but you are reporting a longer lens giving the hot spot problem.

Patrick

[Ian]

Re: The danger of hot spots with infra red photography

I have used two Olympus super wide angle lenses without any hot spot problems (the Zuiko Digital 7-14mm (14-28mm FF equivalent) and the m.Zuiko 9-18mm).

As my article says, the issue is not specific, it could be any focal length and any price lens.

Ian

[Patrick]

Re: The danger of hot spots with infra red photography

I have used two Olympus super wide angle lenses without any hot spot problems (the Zuiko Digital 7-14mm (14-28mm FF equivalent) and the m.Zuiko 9-18mm).

As my article says, the issue is not specific, it could be any focal length and any price lens.

Ian

As things can be so random perhaps it may even extend to specific examples of any given lens.
Reason for saying this my Sigma 10-20 gave a hot spot on the converted Canon, a friend who uses a converted Nikon also with a Sigma 10-20 has no problem.
Don't know how fare you can take your research to find out.

Patrick

[Ian]

Re: The danger of hot spots with infra red photography

As things can be so random perhaps it may even extend to specific examples of any given lens.
Reason for saying this my Sigma 10-20 gave a hot spot on the converted Canon, a friend who uses a converted Nikon also with a Sigma 10-20 has no problem.
Don't know how fare you can take your research to find out.

Patrick

This is an interesting point - thinking about it, the camera itself could be a factor if the mirror box (if present) and other surfaces behind the lens reflect infra red.

On our Four Thirds User site we can try our best to compile a compatibility list as it is a specialist site but it would be an enormous task to cover all brands.

Ian

[devilgas]

Re: The danger of hot spots with infra red photography

i got those hotspots when using an IR (R72?) 55 or 58mm filter. it only fitted to the canon kit lens, and given the IR blocking filter was still in place on the camera, the lens was opened right up. i just thought it was a reflection between lens and filter.
i think the 10d that patrick mentions is the one that is now in my possession, so having seen this, i'll need to try that camera with different lenses this afternoon (obviously without the 72 filter). it also reminds me that i still haven't seriously tried IR astrophotography with it, so will need to look at that tonight maybe ;-)

[Patrick]

Re: The danger of hot spots with infra red photography

i got those hotspots when using an IR (R72?) 55 or 58mm filter. it only fitted to the canon kit lens, and given the IR blocking filter was still in place on the camera, the lens was opened right up. i just thought it was a reflection between lens and filter.
i think the 10d that patrick mentions is the one that is now in my possession, so having seen this, i'll need to try that camera with different lenses this afternoon (obviously without the 72 filter). it also reminds me that i still haven't seriously tried IR astrophotography with it, so will need to look at that tonight maybe ;-)

I had a collection of five Sigma EX lenses, it was only the 10-20 that suffered the problem plus it did not get sharp results, the same lens on a none converted camera was tack sharp
I would therefore be interested in your tests using different lenses, the people in Norwich that converted it insisted problems only showed with super wide lenses, clearly this now appears not to be the case.
Rummer has it 4/3 cameras are particularly suited to IR conversion interesting to to find out if this is indeed true.

Patrick

[Ian]

Re: The danger of hot spots with infra red photography

An advantage with all compact system cameras as opposed to DSLRs is that the AF is determined by the image sensor so in theory your shots will not suffer focus error because of the infra red focus shift. SLRs have separate sensors for AF and these would need to be recalibrated and filtered.

Ian

[Patrick]

Re: The danger of hot spots with infra red photography

An advantage with all compact system cameras as opposed to DSLRs is that the AF is determined by the image sensor so in theory your shots will not suffer focus error because of the infra red focus shift. SLRs have separate sensors for AF and these would need to be recalibrated and filtered.

Ian

The camera was sent back for focus recalobration but the problem persisted, all the other lenses gave nice sharp results. The lens I used most for IR was a 17-35, as sharp as you could wish for, and no hot spot.
I must say it surprises me that filters could cause a problem.

Patrick

[Graham_of_Rainham]

Re: The danger of hot spots with infra red photography

This may well be of interest: lens hot spot data