View Full Version : Focus Shift For Infra-Red

Baxter Bradford
10-Mar-2002, 02:57
I am keen to try Mono IR film initially on 6x12 roll film back on my Ebony RSW (therefore no focus scale), before I try to source 5x4 sheet. I am not sure how to compensate for the focus shift once I've correctly set-up the shot in the normal way on GG. I normally take an SQA with me so might be able to use the focussing on this in some way.

I shoot landscapes using 120mm and 90mm lenses and generally am looking for full front to back sharpness.

I can't recall seeing any mention of this in the books I've read, but am prepared to buy books if necessary.

Also in UK we are awaiting this years batch of Konica IR, are there any other films in 120 (and 5x4) which I ought to consider.

Sandy Sorlien
10-Mar-2002, 12:09
Keep in mind I have not used the IR film you mention, nor any LF IR film, but am very familiar with the Kodak 35mm version, having used it constantly for 15 years.

I would not worry about focus correction unless you are using a visually opaque deep red filter or are doing closeups with limited depth of field. Visual light and infrared light sometimes focus at a different place because the wavelengths are different (IR waves are longer). But unless you're using one of those opaque IR filters, your exposure will be a mixture of both kinds of light. So if you're using a medium red (recommended for most applications) or orange or yellow filter, and you correct for IR, then the visual light may be off. A decent amount of depth of field will take care of both.

The Konica film (also the Ilford SFX) is not a true infrared film - it's red sensitive, but not very far into the IR spectrum. So you don't have to do any focus correction for that, even with the opaque filter.

It is more important to bracket for exposure than adjust for focus.

Steve Clark
10-Mar-2002, 12:50
I thought Konica was out of the IR business. Does anyone know if it will in fact be available? Thanks, Steve

Dave Erb
10-Mar-2002, 12:58
Baxter -

The only IR film I'm aware of is MACOPHOT IR 820c Infrared film, available in both 4 x 5 and 120 sizes. It has different characteristics from the Kodak HIE film, but is a useful substitute. I had heard that Konica had planned to stop making their IR film as of late 2000, but found some in stores in May, 2001.

As for focusing, the books I've read aren't real helpful either. Typically with large format, stopping down to f-22 or smaller should reduce the out-of-focus problem. Given that you appear to be using wide angle lenses, you may be able to get away with a wider aperature.

Best of luck.


Chet Kwapisinski
10-Mar-2002, 23:54
Not sure why this morning's post did not materialize.

Hello Baxter,

Since IR has a longer wavelength you need to adjust your focusing a smidgen. If I remember correctly, the formula is .0025 % (1/400) of the focal length which should bring the infrared image into sharp focus. I normally have no problem with sharpness as typically set my aperature around f22 on 4x5 as well as 6x7 (f16) and do not adjust my plane of focus. Also consider looking at Maco 820 as it presently comes in 4x5 and no ther IR film is commercially available in that format. Both Konica and Maco are fine grain and slow compared to HIE. You may find someone has some frozen some 4x5 HIE and sells it periodically proir to being discontinued by Kodak.

If you plan to get into IR, I suggest the following site to learn about experiences of others as well as a plethora of technical info. Everything you wanted to know about IR but were afraid to ask.....




Chet Kwapisinski
11-Mar-2002, 00:07
I forgot to mention that I have experimented with many of the various infrared "type" films" and various developer combinations and for those that want to shoot HIE in a 120 format (cut down from 70MM) or for that matter 220 HIE. My source for this film can be located at:


I do not want to provoke a discussion on IR but what sets HIE apart from the other films (in addition to degree of IR spectrum) in the lack of an antihahlation backing on the film. With certain developers and appropriate dilutions Konica and Maco can be developed to approximate the "wood effect" etc.... IMHO... good luck to all. Baxter, KOnica IR can be loaded in normal light but HIE primarily in total darkness unless your source of film is at the URL above where subdued lighting works very well based on my limited experiences. Cheers, Chet

Sandy Sorlien
11-Mar-2002, 13:15
Chet, what do you mean by the "wood effect?" Is that a typo? The "wool" effect maybe? The "good" effect?" the "mood" effect? I'm being silly but I never got any "wood" effect with HIE.

The word "effect" is starting to look a little strange too.


Mark Kallfass
12-Mar-2002, 06:59
I`ve solved the problem of focus shift in this way:

put the Kodak Wratten No. 87C an the lens, focus the sun - it works fine! Then m ark your lens extension - pictures of landscape are shape.

I have't any problems with Kodak IR Sheet film and even the old ORWO I 950 Platt e has the right sharpness!

There is one problem: some people (not colour-blindly!) (are not able to see the red light which is coming through the filter (it depends on your seniblity of y our eyes).

Mark Kallfass

Dave Mueller
12-Mar-2002, 16:11
Sandy, The "Wood effect" is what you call the lightening of foilage in IR. It is named after the guy who discovered it. Check WJ's Infrared Page for lots and LOTS of info.


Chet Kwapisinski
13-Mar-2002, 00:26
Trees and grasses appear to glow white and radiate when illuminated by an IR light. This effect is often called the ?Wood Effect.? It doesn?t refer to wood but to R.W. Wood, a pioneer in the field of infrared film. Wood actually is fairly dark on IR film.


16-Jan-2017, 11:41
Have a question about focus compensation: do I compensate towards or away from the lens? Do I want to focus to infinity, or closer inwards?

And would anyone know how to calculate the same compensation for UV? I bought an old 135mm EL-Nikkor and B+W 403 filter six months ago and finally am ready to give it a try.

16-Jan-2017, 12:38
Have a question about focus compensation: do I compensate towards or away from the lens? Do I want to focus to infinity, or closer inwards?

And would anyone know how to calculate the same compensation for UV? I bought an old 135mm EL-Nikkor and B+W 403 filter six months ago and finally am ready to give it a try.

Closer for infrared, away for UV. The correction is more critical for close-up work. For distance scenes the depth-of-focus and smaller physical aperture for depth-of-field usually makes up the difference.

May we ask what film and lighting you are using?

16-Jan-2017, 16:08
EB/RA Carestream film is what I'm using for the UV stuff. Figured to use it in full winter daylight.

15-Nov-2019, 18:16
I'm back, years later, struggling with focus compensation for UV. I'm supposed to be focusing as if the subject is slightly further away from the camera, right? I'm using an enlarger lens, which means that the lens should have less distance between it and the film than when the subject is in focus in solely visible light, correct?

16-Nov-2019, 08:12
I have never bothered about changing focus for IR film (Maco), I usually stop down to f16 f22, and I have not noticed a focus shift, the DOF takes care of it in my case, I mostly shoot landscape. I guess the same will hold true for UV, the detectable wave lengths will be close to visible I assume.

good luck,


16-Nov-2019, 21:28
I have also never compensated, using the opaque IR filters and Konica imagesetter film. Never been an issue with normal landscapes, I imagine critical focusing on a portrait with a wide-open f3.6 Petzval might require a minute correction. When I initially tried, I checked my old Canon FD lenses of similar focal length to what I was using in 4x5, because they had a red dot on the focus scale to help adjust. So I figured that if the 200mm lens required focusing at 15ft to get 18ft in focus, I could simply focus my lf camera on a measured object accordingly. It didn't work, my initial experiments were all failures, so I stopped down to f16 and just shot normally.

Jim Jones
17-Nov-2019, 08:37
Rudolf Kingslake recommended moving the lens closer to the subject by about .5% of the lens focal length in his 1950 Lenses in Photography. However, this is a generalization. The corrections for specific lenses published at that time by his employer, Eastman Kodak Company, sometimes very considerably from that general formula, even among lenses of one design but various focal lengths.

Pere Casals
17-Nov-2019, 08:56
Every lens has a different shift for IR, some are corrected for ir not requiring a shift

A solution is stopping more to extend DOF

17-Nov-2019, 13:41
Every 35mm and medium format lens I have looked at with an IR focusing mark requires the lens to move further away from the film for the IR, ie the lens has a longer focal length in the IR. Presumably the lenses would have a shorter focal length in the UV.

This is sort of understandable because dispersion makes the index of refraction of glasses decrease at longer wavelengths, so at longer wavelengths a simple glass lens has less refractive power and a longer focal length. https://en.wikipedia.org/wiki/Dispersion_(optics) However, multiple element optics may not follow any simple formula. if you look at the IR focusing mark for a very complex lens like a zoom, it may have a much larger IR focus shift than a fixed focal length lens. Fixed focal lengths are more usable at the extremes of wavelength, and it's not possible to simply transfer the distance from one lens to another of different design, so educated guesses, stopping down, and experimentation are your friends. Some lenses are more suitable than others - it also depends on the glass types and coatings.

19-Nov-2019, 11:39
So stopping down should work, because I need to compensate by focusing the image as if it was further away, since technically it is focused "too close" when focused in the visible range?

I just had some really disappointing results with two reels of 35mm, and I'm trying to understand whether my models are moving, or whether I'm missing focus compensation. I always shoot stopped down to f/11. It's easily possible for the models to move, because I have to first focus in visible light, and then throw the visible range-blocking filter on the lens, after which I turn on the LEDs. There's ample time for them to shift, even as they try as hard as they can to stay still. However, I'm also wondering now if the split-image focusing screen is causing problems, because I've noticed that it doesn't work very well with the lenses I use for UV photography- one half of the split image is always a little dark, making it very hard to see whether the two halves are aligned, and the image surrounding the split image doesn't always seem to be in focus when the split image is.

19-Nov-2019, 15:19
I don't have any direct experience with UV photography. Pretty much every lens is going to have a focus shift in the UV and IR, and the sense of the focus shift will usually be shorter focal length in the UV, meaning when you focus the lens in the visible the value on the focusing scale will be "too close" in the UV. Stopping down helps because stopping down gives you greater depth-of-field / depth-of-focus to compensate for focus errors. I would try adjusting your focus to shorten the distance between lens and camera by a small amount, and stopping down more than f/11.

The other thing is, clearly you should do a focus test with your UV setup and a static subject. If you try a yardstick at an oblique angle to the camera, you can measure the focus shift (like, lens focused in the visible at 1 meter on the center of the yardstick, but the part of the yardstick that comes out in focus was at 1.1 meters from the camera), and then you'll just know what the shift is for your particular lens.

Split images darken when the lens is slower than f/5.6 or so, for geometrical reasons.

Gary Beasley
19-Nov-2019, 16:15
So stopping down should work, because I need to compensate by focusing the image as if it was further away, since technically it is focused "too close" when focused in the visible range?

Thats backwards of the way it works. The ir mark sets the lens slightly farther away, so you should compensate an unmarked lens by focusing slightly closer (which moves the lens further away).

19-Nov-2019, 16:34
Gary, I'm talking about shooting in the UV, which I presume is the opposite from the technique for shooting IR. Thanks reddesert, I had no idea about the split image. I can post some examples of the 35mm exposure I think are quite off:


Please ignore that the poses and subject matter are bizarre, these were mostly trials. At first I had thought that perhaps my scanning mount was out of focus, but even when corrected, the scans are still pretty blurry. These were all taken tripod-mounted, at 1/8 of a second or faster. I'm either over- or under-compensating, paired with perhaps a failure to I know that these two reels were off, because the reel before them produced results like this:


Nothing about my methodology changed significantly. I don't do anything to my scans in BW except make minor adjustments to contrast and brightness.

19-Nov-2019, 16:44
Here's another example of the sort of fine focus I can achieve when stopping down on 35mm (and when all the unknown variables that I am trying to deduce go right).

4x5 is even more difficult. I'd say I only get about 1/3-1/2 of those in focus, on average, when I'm shooting UV. Generally I fall short a bit, like here:


But I've also managed to nail it, like here:


I have no idea what is going on between these exposures, except that perhaps the models are moving ever so slightly in the interim where I install the filter and turn on the lamps. What makes this more frustrating is that generally these scenes are simple enough that there isn't enough material, either behind or in front of the subject, for me to discern whether I fell short or focused too far.

Gary Beasley
19-Nov-2019, 18:11
Have you tried laying a ruler out and shooting visible and uv without changing the focus? You might see the focus shift directly in the image and be able to figure out the problem.

21-Nov-2019, 11:59
For 4x5 that would quickly become prohibitively expensive.

21-Nov-2019, 13:36
For 4x5 that would quickly become prohibitively expensive.

You're burning film right now without knowing the focus shift.

You need to set up a static subject - try a yardstick (meter stick if not US) laid out at say a 45 degree angle to the camera, with its center at your normal portrait distance, so that the left side is closer to the camera and right side is further away. Measure the distances at some fiducial points, for example say the 18 inch mark is 60 inches from the film plane, the 12 inch mark is 56 inches from the film plane, the 24 inch mark is 64 inches from the film plane. Focus in the visible on the center of the yardstick at the 18 inch mark. Expose the film in the UV at your normal working aperture. Examine the negative with a loupe to find the point that is in best focus. Now you know your focus shift for your combination of lens, filter, and film, rather than having to guess from unknown rules of thumb.