Lens Calibration on IR conversion

Herb Cunningham · Jul 23, 2009

I am sending a camera to a group that does IR conversion. They recommend I get the lens I will use calibrated to the IR filter. ($125 extra). Anybody have experience with this? Depth of field is important, although my lens would be a 24mm, used on a crop sensor camera, or 1.6x.
And thus the depth of field would be pretty good to begin with.
Don't want to be cheap, but it seems a charge I might do without.

pellicle · Jul 23, 2009

Hi

Herb Cunningham said:
I am sending a camera to a group that does IR conversion. They recommend I get the lens I will use calibrated to the IR filter. ($125 extra). Anybody have experience with this?

well, not with DSLRs but I found that the contrast detect AF works a treat without any calibration on my Coolpix although on my panasonic I expect it needs a conversion as the sensor sees only blackness for the viewfinder and needs long exposures.

I guess it depends on if the phase detect can see much.

Alternatively you could do what I always did on my Film SLR and that is to work on a tripod, focus, fit filer, correct focus and take

Mike Richards · Jul 23, 2009

I assume you're referring to an SLR of some type, where the visible light focus in the viewfinder won't match the focus of the IR sensor. Not sure what it involves to calibrate the lens, but you can run a series of tests on any lens wide open on a tripod at varying focus settings to determine the offset for IR. This will be different for each lens. Once you get the offset right, you need to crank it in after focusing visually. You can then run DOF tests by varying the aperture. This is basically what I've done with a converted Nikon D100, and it seems to work out ok. I use a manual focus 28mm Nikor AI almost all of the time and got some great images. I was not offered any lens calibration when I had this done some 4 years ago, so I'd like to know what the $125 does? Does it affect autofocus lenses only?

Herb Cunningham · Jul 23, 2009

Lens calibration for IR

Mike, I am not sure about the autofocus question. Once the camera is converted (Canon 50d)
the story is that IR is adjusted automatically.

I will ask the vendor about it and post a reply.

sanking · Jul 24, 2009

Herb Cunningham said:
Mike, I am not sure about the autofocus question. Once the camera is converted (Canon 50d)
the story is that IR is adjusted automatically.

I will ask the vendor about it and post a reply.

I am very interested in how this turns out as I have a 50D and am thinking about having it converted to IR. Not so long ago I had a Canon G9 converted to IR by the folks at www.maxmax.com and I very pleased with the results, but when all is said and done I would probably be happier with an APS sensor since I am looking for MF type sharpness in print size up to 13X19. Amazingly, the converted G9 is not far off, with some interpolation.

Prior to having the G9 converted I had not done much work with IR. Now I am pretty amazed at the kind of imagery that one can find in full sun with scenes of high contrast where it would be impossible to do any interesting work with regular B&W.

Sandy King

Pinholemaster · Jul 24, 2009

I had my camera (Nikon D200) converted to Infrared. The company conversion process was set for a Nikkor 18-70 mm zoom. If I wanted to use a different lens on the camera there would be an additional $125 charge for calibrating the CAMERA to that lens.

The lens is not calibrated. The camera sensor is calibrated to the lens of your choice. Once calibrated you can attempt using other lenses, but you'll have to test them to learn whether the depth of field will carry to cover the IR focus shift that all lenses have.

Hope that is helpful. Once done, I've loved the results. The auto-focus tracks perfectly in IR.

Herb Cunningham · Jul 24, 2009

Conversion of DSLR to IR

Walt Calahan said:
I had my camera (Nikon D200) converted to Infrared. The company conversion process was set for a Nikkor 18-70 mm zoom. If I wanted to use a different lens on the camera there would be an additional $125 charge for calibrating the CAMERA to that lens.

The lens is not calibrated. The camera sensor is calibrated to the lens of your choice. Once calibrated you can attempt using other lenses, but you'll have to test them to learn whether the depth of field will carry to cover the IR focus shift that all lenses have.

Hope that is helpful. Once done, I've loved the results. The auto-focus tracks perfectly in IR.

Ok, I spoke with the vendor, and he explained that they calibrate focus with a lens wide open. If it is a zoom, they use halfway as the focal length.

Since mine is a prime, I can shoot wide open and not worry about being in focus, as that is where they calibrate the lens. Makes sense. Also means I will have to check out where other lenses might have a problem at wide apertures.
The wide open fits my agenda perfectly, as I planned to do some old buildings in shade with bright sun peeping through parts of them.

Sandy, I will post a shot or two when I get the camera back.

sanking · Jul 24, 2009

Herb Cunningham said:
Ok, I spoke with the vendor, and he explained that they calibrate focus with a lens wide open. If it is a zoom, they use halfway as the focal length.

Why would the calibration matter if you use focus with live view, which is what I would plan to do with the 50D?

Sandy King

donbga · Jul 24, 2009

pellicle said:
Hi

Alternatively you could do what I always did on my Film SLR and that is to work on a tripod, focus, fit filer, correct focus and take

Correcting the focus was totally unecessary IME, particulary when hyperfocal distance focusing.

Don Bryant

Mike Richards · Jul 25, 2009

Walt Calahan said:
The lens is not calibrated. The camera sensor is calibrated to the lens of your choice.

Doh! Should have thought of it. This makes perfect sense.

pellicle · Jul 27, 2009

Don Bryant said:
Correcting the focus was totally unecessary IME, particulary when hyperfocal distance focusing.

Don Bryant

definitely with my 24mm I agree ... I've also played with the 90mm lens and its more important there.

I'm interested to see how well a 4/3rds camera may go as an IR camera. On another forum a fellow has shown his converted 420 ... not sure how well that focuses in live view, so a G1 (or even a E-P1) might be a better choice.

meantime I'm too cheap for such and will remain on film for a while (hmm ... anyone know of a 4x5 sheet film which works like HIE??)

Herb Cunningham · Jul 27, 2009

Calibration for IR conversion on DSLR

I emailed the vendor once again, and Sandy, he said he agreed that calibration was not needed if you are using live view. The only instance he could think of was if the lens required going past the infinity mark, something I would think quite unlikely.
On the other hand, being old and not seeing the view screen well at all in sunlight, I opted for the calibration. I may wind up getting one of those snout things to look at the view screen with, though.

pellicle · Jul 27, 2009

hi

Herb Cunningham said:
On the other hand, being old and not seeing the view screen well at all in sunlight, I opted for the calibration. I may wind up getting one of those snout things to look at the view screen with, though.

this is the thing that I love about my G1 ... the EVF is of course both sheltered and diopter corrected (my dark cloth is getting too short on my 4x5 too ;-)

Lens Calibration on IR conversion

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