[LRflex] Re: Comparison of M8 Photos in Infra-Red.
- From: David Young <telyt@xxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Mon, 20 Nov 2006 08:52:40 -0800
Colin Howarth noted:
> > Now we have B&W mode (as selected in the M8's menu) - no IR filter
> > used.
> >
> > http://www3.telus.net/~telyt/M8_BW_Normal.htm
> >
> > And last, the M8 in B&W mode, but with the IR filter attached.
> >
> > http://www3.telus.net/~telyt/M8_BW_IR.htm
>
>Well, the BW shot without IR filter seams much clearer...
Good Mornin', Colin!
Hmmm.... you are right.
They "should" be all the same as they were taken on a tripod, using
the self timer - as I had no cable release with me.
My standard practice is to add 1 pixel of sharpening (Focus Magic) to
compensate for the loss of sharpness when reducing the size for web
use. Thinking I might have forgotten that, I tried it again.... and
then again with 2 pixels of sharpening. Still, there was no
noticeable improvement.
Even more interesting is that the colour IR image is also not as
sharp as the regular colour image. The question of the hour.... "Why?"!
In case is was a matter of bumping the tripod, I went back and
checked other scenes I'd shot for IR/normal comparisons. They are
all the same... the IR shots are noticeably "fuzzier".
This made me think... something I should have done earlier!
If you look at the shots, the main area of "unsharpness" is in the
reeds. It was fairly breezy, out by Tunkwa Lake, that day. The
colour and B&W (normal) exposures were at 1/360th of a
second. However, the IR exposures (both B&W and Colour modes) were
taken at 1/30th... allowing the winds to move the reeds and make the
photos look unsharp. (I'd simply had the M8 on "Auto".)
Still, the trees in the distance and even the outline of the hillside
look less sharp in the IR shots.
This would be explained by the fact that IR shots on ALL lenses
(except some APO ones), whether using film or digital, require
adjustment of the focusing to bring the IR wavelengths into focus on
the film/sensor plane. I had forgotten that fact, when I made the
shots, and the borrowed lens I used had no compensation mark (some
do, many do not). Thus, I made them all simply focused on
infinity. (A poor choice!)
Had I remembered, I could have carefully examined the LCD screen (on
magnify) and repeated the exposures, over and over, each one with a
slightly different focus, until the correct point was
found. However, time was limited, and memory was short. The result
is the difference in apparent sharpness.
Sorry, I should have explained all of this in my first post, but I
hadn't noticed, as I put the pages up in a huge hurry.
Still... the shots illustrate the IR sensitivity of the M8.
For comparison, here are two shots taken with the R8+DMR, using the
IR filters. Obviously, the DMR is much less sensitive to IR, as the
same exposures required +3 stops of compensation during
"development" from the DNG files. Thus, much, much more
noise. Totally unacceptable for IR use, but interesting, nevertheless.
R8+DMR - Normal colour shot...
http://www3.telus.net/~telyt/R8_Colour.htm
R*+DMR - B+W IR shot..
http://www3.telus.net/~telyt/R8_BW_IR.htm
Cheers!
---
David Young,
Logan Lake, CANADA
Wildlife Photographs: http://www.telyt.com/
Personal Web-pages: http://www3.telus.net/~telyt
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