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Wednesday, 07 August 2013

Comments

Ctein,

Does the relatively poor dynamic range of the Olympus E-P1 cause much trouble when it comes to infrared photography?

I shot briefly with an E-P2 a few years ago and was never very happy with the sensor's ability to capture high contrast scenes without blowing out highlights or blocking up shadows that showed lots of noise when trying to bring them back a little.

I ask because infrared images often seem pretty "hot" to me, lots of delicate and bright whites. The last image in this blog post illustrates the problem well with what appear to be blown-out highlights in the grass.

Good summary of the challenges. Your list does not actually surprise me :-) My experience has been that it's easy to find tele lenses that perform well, while wide angles are a different story. I remember how my old Nikkor 85/1.8 was razor sharp, while getting a wide that holds corners well was a big challenge, especially in wide band photography. Now that I've optimized for a very compact IR kit, I'm finding problems with evenness of illumination in superwides and strong IR filters, my RG780 giving me very dark corners. Such is life.

But while I read this post, the foremost thought I had was that it's all relative. Slightly blurred corners? one could crop or compose differently; a nuisance for sure, but workable. Similarly, the serious hot-spot of the 60/2.8 doesn't look nearly as bad as I got from a good and not complicated normal lens. But hot-spots depend a lot on subject matter. Sure changing the way one shoots due to lens deficiencies is a nuisance, but sometimes it's easiest to just live with certain limitations.

I use a converted GX1 and have similarly found some lenses not to perform well. The Panasonic 14-45 is poor at the wide end but much better at 45mm. The Olympus 9-18 is pretty impressive although also suffers a little at the wide end. MyOlympus 45mm is also very good as is the Panasonic 45-200.

Something else I have noticed is some of the UV filters I have used have degraded the image or caused hot spots. I have now switched to using clear glass protectors.

Great to find someone else also using Micro 43 Infrared. Thanks for sharing your findings.

Dear Josef,

Not, not at all a problem. Please read last week's column. Also, there are no blown out highlights in Figure 4.

pax / Ctein

Thanks for the useful info about which of your m4/3 lenses are IR-capable. I shall add a link to this column (and the last) in our IR reference Sticky.
It's nice to see you shooting IR. "-)

Ctein,

For the uninitiated, could you please explain "hot-spotting?" What is it, what should I be looking for in the example, and what causes it, optically?

Ctein, please keep up the IR posts, it great to read more on this.
I am not too surprised by the Olympus lenses doing well. I think the new coatings allow IR through, and its rumored that Olympus uses the IR to assist for rapid contrast focusing. So the camera and lenses I would expect to do well in IR now.
I must say you eyes must be different than mine. I don't see a severe hotspot in figure 4, actually I don't think I see any hotspot. The ones I have found/seen over the years are blatant. As in a bright sun now magically appears in your shot. The circle of light was never there before.

hi there Ctein,
I just received my IR-converted EP2 a week ago, got it modified by a Canadian store in Quebec. I have been using it with my Olympus zooms, 9-18mm and the telephoto 40-150mm with great results. I suppose when I say "great results", I am so accustomed to to working on images in photoshop that it is normal for me to spend time with a single image, just like in the past when spotting archival silver prints.
Anyway, it's a great change from my Fujifilm IS-1, factory-made as full-spectrum IR, which had the most annoying lens-flare.....
IR isn't for everyone, but there is a beautiful creative dimension if we put in the work...

Dear Will and DavidB,

Well there are two kinds of hot spotting, although both are caused by the inability of the lens design and anti-reflection coatings to suppress stray infrared light.

The kind I'm describing is an overall diffuse glow, where the center of the field is suffused with veiling light. That's what you see in figure four. The dark tree trunks and shaded grass there aren't brighter because of any real-world lighting effects. They should look as dark as the similar objects at the periphery. Clearly they don't! It'll happen to a greater or lesser degree with any scene, no bright lights in the frame required.

Because anti-reflection coatings often don't work well in the IR, you can also get flare and ghosts, just like you would from pointing any lens at a very bright light source, but much much worse in the IR. That's a more normal problem, and you deal with it in the IR the same as you would in the visible-- "Doctor, it hurts when I do that." "We'll, then don't do that!"

pax / Ctein

The 12-50 "kit" lens that I bought with the EM5 is also surprisingly good with no hotspots. I've used it on a converted GF1

I'm running into this exact issue trying to find good m4/3 lenses for IR. I have the 14-42mm zoom and while I am satisfied with it, I would like to have something a little more compact for travel (like the 20mm or the 14mm). I found some people saying the 20mm was a fine IR performer, but here you are proving them wrong, so I'm not certain what to think about the 14mm (which the same people said was good as well). I'm starting to think the reviews merely look for hotspots. Sigh, I wish there were more m4/3 IR shooters so we could have more reliable reviews.

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