[Leica] IMGS: IR Attempts

[Ken Carney]

Hi Howard,

Yes, that is correct.  In my initial tries with digital IR I thought a 
wide-angle at infinity would make things simple, but as you note there 
are different infinities for the wavelengths.  With regard to autofocus, 
I can't offer a technical explanation.  Since the autofocus is based on 
contrast differences, I just assume those work as well in the IR as they 
do in normal light.  Here is a more complete explanation from Lifepixel.com:

https://www.lifepixel.com/focus-calibration-options

Here are some samples mostly all taken with the Fuji XE-1 or XE-2 and a 
Hoya R72 IR filter (and autofocus):

http://www.kencarney.com/infrared

The Fuji cameras have a weak IR filter.  The downside is long exposure 
times and a tripod or monopod (as much as 1/2 second).  I will probably 
soon have a third Fuji XE body which I will probably have converted to 
IR only, and take advantage of normal exposure times.

Ken


On 8/31/2016 8:24 PM, Howard L Ritter Jr wrote:
> Ken—
>
> If you think you can't focus IR because you can’t go beyond infinity, you’re going in the wrong direction. IR focuses as though the subject is CLOSER than it is, so you want to use a DOF marker that focuses the lens at a shorter distance than the subject actually is. For my lens (same as Tina’s) the best “distance" for a subject at infinity is 2-3 meters. Even there I can’t get as sharp an image as with visible light.
>
> No, this 21mm f/2.8 Elmarit doesn’t have an IR index. I’ve seen them, and would have sworn that my older Leica glass did, but not so my vintage 50 ‘lux, DR ‘cron, or 5cm ‘cron. I have no idea where I used to see them, but clearly IR is out of fashion now.
>
> I’m intrigued to hear that you can get properly focused IR images with an AF lens. Are you shooting digital? I’d have thought that the IR filter routinely used as a sensor cover glass in digital photography (except for the M8!) would have prevented this. Or are you using film? If digital, what camera? And what filter are you using?
>
> —howard
>
>
>> On Aug 31, 2016, at 8:50 PM, Ken Carney <kcarney1 at cox.net> wrote:
>>
>> Looks like you're pretty close.  I think the key to IR is autofocus, not an option here.  You might try a few shots at different focus settings to see what works with the M8/21.  I know my Fuji X 14mm is OOF when it is at his hard stop infinity setting, with a 720nm filter, but autofocus if fine.  Also in LR I like to pump up the whites and decrease the blacks some.  It is great that you can make IR images at those settings, freeing you from the tripod.  I take it that the 21 does not have an "infrared" focus mark?
>>
>>
>> On 8/31/2016 6:49 PM, Tina Manley wrote:
>>> LUG:
>>>
>>> After seeing the great IR photos posted here lately, I finally dug out my
>>> old M8s (the ones that fell in the river but are still working fine),
>>> charged up the batteries, and found a B+W 092 filter in the drawer that fit
>>> my 21/2.8 Elmarit.  I went out around the farm and photographed a few
>>> things.  Lots of problems.  Nothing looks sharp.  What am I doing wrong?
>>> None of the EXIF is right.  Most of these were made at ISO 160, around 5.6,
>>> and usually 1/30 or more exposure.
>>>
>>> http://www.pbase.com/tinamanley/image/163998663
>>>
>>> and the next 5.   Is there a trick to focusing with the dark filters?  I do
>>> like the tones so I would like to learn how to do this, but it has to be in
>>> focus to work for me!!  I got some great photos of the cat yawning that are
>>> so out of focus I won't bother to post them!!
>>>
>>> TIA
>>>
>>> Tina
>>
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