Hot spots in IR with different lenses

[Herbc]

I just had a Sony A7r converted to IR, as I shoot a lot of landscapes in IR.  The Sony 35mm has a serious hot spot on the converted camera.

Question: in looking for alternative lenses, is there any type of construction or coating that would be a clue as to mitigating the likelihood of hot spots?  For example, more elements in more groups, or older lenses without the modern coatings?   Perhaps older Tessar lenses? The camera of course will only do b/w IR, so no need to get fussy about color renditions, etc.

  I do plan to test what I have, of course,  but the 35mm focal length is pretty much my go to lens.

[Telecaster]

This is something I haven't got into yet with my A7r. Did you try doing IR via lens-mounted filters before you had the camera converted? If so how was IR response? I ask mainly because I wouldn't mind doing a bit of IR photography on an upcoming trip, but the weather where I live has been so unrelentingly crap I've hardly been outside long enough during the past two months to set up a tripod much less take photos. My hunch is that older lenses with less "advanced" coatings will do better IR-wise than newer ones...and since I have quite a few such lenses I'd be willing to give some of 'em a spin.

(BTW, our average high temp over the past six weeks has been 20°+ F below normal. Grrrr...)

-Dave-

[Herbc]

I did not try IR with filters.  This will be my fourth digital IR camera, but I did shoot a lot of Rollei IR 400 a few years back.  The long exposures and the winds we have here in NC gave me fits, so I gave up on the filters.  I do have the Sigma "Art" 35, I will have a go at that, and the local dealer is quite willing to loan all manner of used lenes, so I will post results probably in  a month or so.

[kaelaria]

I used to have an Ir converted Canon body, but like you found most of my lenses useless for it.  One of the reasons I stopped.  I saw years ago a list of lenses that were ok to use, but I can't find it now.  It was a short list and I don't recall what about them made them good or not.

Ah - just found the link as I was posting lol  http://www.kolarivision.com/lenshotspot.html

[Robert DeCandido PhD]

I use a Canon 5D2 all the time for IR work (modified for IR) - and it is wonderful...no hot spot issues at all with any of the lenses I use including the 24-105 F4; the Tamron 24-70 F2.8; and the CY 35-70mm F3.4 zoom...

For a list of lenses that cause/do not cause hot spots, see this post from FM forums:

http://www.fredmiranda.com/forum/topic/943179/0#8913758

and http://www.fredmiranda.com/forum/topic/1103898/0#10534625

my IR work from Central Park: http://photo.net/photodb/folder?folder_id=637107

and some in this portfolio - The Bronx River: http://photo.net/photodb/folder?folder_id=399445

[Herbc]

Glad to hear the Nikon 14-24 does not hotspot, I have that lens,  and the 85PC 

.
I have the Samyang/Rokinon 14 f2.8, will report on that as well as the Nikon 24 P/C, one of my favorites.

Many thanks for the responses.

[alan_b]

Nikon 17-35, 14-24 worked well for me.  50/1.8 has a strong spot, can't remember others.