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stray_227
30-Oct-2013, 04:45
I'm still having focus issues with Efke 820 Aura film - both Medium and Large format. I'm making "the adjustment" - on the little red line and infinity mark on Mamiya 43mm wide angle but also on Kodak Ektar 14" 8x10.

Any thoughts or better guidelines ?

thanks

shawn

polyglot
30-Oct-2013, 05:11
Assuming your images are coming out focused too close, don't make the adjustment. The IR mark on most lenses pertains to much longer wavelengths like 1um (1000nm) that IR820 just can't see.

While there is a small focus error between 650nm (red) and 780nm (the peak sensitivity of IR820+R72), it is very small. Probably smaller than the focus difference between red and blue light with a decent lens.

ataim
30-Oct-2013, 07:19
Also make sure to stop down quite a bit. My normal work flow is to compose and focus under normal conditions, then add the ir720 filter. With it in place that you can still see the ground glass, its pretty dark and I have to be under the cloth for about 30 seconds for my eyes to adjust enough to see. Then I will refocus. But its only a 2-3 millimeters at the most using a 90 mm lens and around 3-4 millimeters on others (4x5), if at all. When I first started using IR film I was WAY over compensating for focus shift and not stopping down enough.

vinny
30-Oct-2013, 10:41
I've never compensated for large format efke ir films. Compensation does vary between individual lenses but it's so small that I don't worry about it. My prints aren't soft.

Jody_S
30-Oct-2013, 10:44
My imagesetter film is sensitive well past 850NM, I've always shot at f16 or smaller and never had to make an adjustment for focus.

uphereinmytree
30-Oct-2013, 11:44
I agree with 'no large format focus adjustment needed for efke IR film' I always get sharp images. More sensitive IR films would need adjustment and I do the adjustment when shooting 120 IR in a 645 camera.

drew.saunders
30-Oct-2013, 17:32
When I shoot Efke IR820, I try to focus on the something that's close that I want to be in focus, but don't specifically change focus, and use f/16 or 22 for 4x5. For your 8x10, I'd suggest f/32, 45 or 64, plus a lot of patience!

Leigh
30-Oct-2013, 17:52
At the shooting apertures commonly used for LF work, the IR shift will usually be well within the depth of field.

- Leigh

stray_227
30-Oct-2013, 18:55
Thanks folks - lot of good advice which I really appreciate! I've just gotten to the point where I think I have the exposure down - which took a LONG time - this film is tuff and I'm a rookie - but I'm committed. Will have to deepen my tests on the focusing front now.

thanks again for all of the great comments!


On a different but related topic - if people have specific developer suggestions for this film I'd love to hear about that as well

shawn

Joseph O'Neil
5-Nov-2013, 08:41
Stop down as much as you can. Also, I find that focusing with IR is more critical if you are using longer focal length lenses (210mm or longer for 4x5, for example) and if you have any of it around, the old Kodak HIE was more sensitive than the newer IF films. I think, not sure, the old HIE went to at least 850nm

If you ever do a IR conversion on a digital SLR, feel free to e-mail me off forum, I did that with one of my D7000s, and it is great fun. For what it is worth, if you can shoot 4x5 IR, you will take nicely to a digital IR conversion.

good luck

Carsten Wolff
6-Nov-2013, 07:00
AA suggested, you'll e.g. find it in "The Camera" I think, to advance the focus by 1/32nd of the focal length....but its easily been 10 years since I read that. I can't remem ber any mention on what that is based on and for what part of the IR spectrum that may apply, but one can assume for the run-of-the-mill b/w IR film at the time.

vinny
6-Nov-2013, 07:35
As I said earlier, the compensation for all lenses isn't the same. That's coming from schneider optics, not something I read on the back of a cereal box. The 150 apo-symmar I had required something like 1-2mm of extra bellows but they didn't specify any film/filter combination.

polyglot
6-Nov-2013, 22:28
AA suggested, you'll e.g. find it in "The Camera" I think, to advance the focus by 1/32nd of the focal length....but its easily been 10 years since I read that. I can't remem ber any mention on what that is based on and for what part of the IR spectrum that may apply, but one can assume for the run-of-the-mill b/w IR film at the time.

He probably did say something like that (I had 1% in mind but whatever) and it was probably true when he said it. However with modern lenses that exhibit more uniform behaviour with respect to wavelength (a result of reducing chromatic aberration, mostly), the correction is far smaller. A 3% extension would probably be a gross overcorrection with most plasmats.

Joseph O'Neil
7-Nov-2013, 08:09
If you plan to shoot something that is important or "mission critical " by any means, go out and waste a few sheets fo film testing. Settle on one or two lenses only (makes life simpler), do a bumch of shots of the same thing, and mark on your camera with something temporary (like post it notes) your various focus setting, take notes, develop film, see which focus setting worked best, mark with a sharpie on your metal rail those focus marks.

Takes a while and costs you some sheets of film, but save you time and money in the long run
joe

Jim Peterson
7-Nov-2013, 13:54
For your medium format (Assuming Mamiya 7 with 43mm) this is what I have done and it came out good. I was looking for everything in focus for landscapes. Don't know if that is your application. Anyway I set the f stop at F16 then put the infinity mark on 8, used a Hoya R72, a tripod, and shot in late May or early June. Most of the exposure times turned out to be 1 1/2 to 3 seconds between about 10:00 AM and 2:00 PM. Hope that helps.