(Fwd) RE: (Fwd) RE: IS-1 various filters and IR sharpness

[WJM]

------- Forwarded message follows -------
From:           Stan Patz <skp113@...>
To:             WILLEM-JAN MARKERINK <w.j.markerink@...>
Subject:         RE: (Fwd) RE: IS-1 various filters and IR sharpness
Date sent:       Tue, 31 Jul 2007 00:06:33 +0000

> I have a larger question for you about IR sharpness - and for the > whole group. Put aside the ethereal glow of HIE, let's talk about > resolution. In my history, I have shot 8x10, 4x5, MF 120 and 35mm IR > film from at least 3 manufacturers. I do not think I have ever seen a > truly sharp IR
photo.> > Now I am shooting digital IR on a converted Sony DSC-R1 and getting > similar results. Nothing is very sharp. ....
> > My theory is that all my optical systems have been optimized for the > visual spectrum. None of my fine lenses past or present has the > ability to critically focus wavelengths going into the IR band. Is > there any science to back this up?
 
To the group,
 
I posed the question and realized that I am in a pretty good position
to answer part of it.
 
The question about IR sharpness is a little more complicated than it
sounds because it refers to optical systems of lenses and filters
coupled to different types of film or digital sensor. Add to that the
newer twist of autofocus and we have a bunch of variables.
 
The camera I am currently using, a Sony DSC-R1 (discontinued after
about 9 months of shelf life) was modified to take either color or IR
photos, depending on which filter is in front of the lens. So I just
did some dull testing - I photographed a double page spread of the
New York Times from about 2 meters at the 100mm(equiv.) setting at
f4.8(max) and f8 with a CC1 (IR blocker), XDP (IR bandpass filter
~750nm) and no filter. I tested with both manual focus, a very iffy
procedure on this electronic viewfinder, and autofocus. Like many new
cameras, the Sony has internal focusing, so there is no engraved
distance scale or trusty mechanical ring linked to a helical gear. It
does have a nice knurled focusing ring, but it is flying by wire.
 
Yes, I shot everything RAW and used similar contrast boosting and
color suppression on the IR (and "no filter") files that I would in
normal IR photography. Much to my relief, the autofocus pix were as
good or better than manual focus. Much to my surprise, I saw no
appreciable difference in sharpness between the three modes.
 
Now that I have one test completed, I will have to look elsewhere. As
I write this, it occurs to me that I am usually shooting at the
24mm(equiv.) end of my zoom. So that is my next test - check
resolution at different focal lengths.
 
I still would like to hear from others who have made large IR prints.
Right now, my theory that all IR photos are mushy looks a little
weak.
 
Stan Patz  NYC Stan@... www.PatzImaging.com
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------- End of forwarded message -------
--                
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand

<w.j.markerink@...>
[note: 'a-one' & 'en-el'!]

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[Breukel, C. (HKG)]

>
> I still would like to hear from others who have made large IR prints.
> Right now, my theory that all IR photos are mushy looks a little
> weak.
>
> Stan Patz  NYC Stan@... www.PatzImaging.com


Stan,

I have shot quite some 4*5 MACO IR film, and I did not notice any
apperant loss in sharpness (that is judging the non ir reflecting
surfaces like stones, bricks, roads etc, leaves are a bit harder, due to
the long exposures needed with MACO ir film). I have to add that I
enlarge my 4*5 quite moderate (upto 30*40cm). That said I recently shot
some Rollei IR (hahah..IR..hardly there even with a 89b, do not have
anything stronger than that), and I got the impression that this film
was sharper. But to draw real conclusions more testing is needed, and
also the developer should be considered since it affects percieved
sharpness

Best,

Cor
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