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Re: [OM] Overextending your reach

Subject: Re: [OM] Overextending your reach
From: "Chris Trask" <christrask@xxxxxxxxxxxxx>
Date: Thu, 29 Sep 2011 15:44:34 -0700
>
> >    I'm going to set up a more definitive test later, but the first thing
I
> > need is a good colour chart or even better one of those lens test
charts.
> > Next time I drop in at the local camera shop I'll see if I can obtain
one.
> > I don't have a colour printer, so it's no point in downloading one.
But,
> > I
> > do have a small Munsell colour circle in my copy of Sidelinger's "Color
> > Manual" that I could use.
> >
>
> I did my normal RAW image processing on the two images, and will post the
> links below.  To me, the Telyt has less contrast, but more detail.  Your
> tastes may vary from mine.
>

    I went over to the local camera shop and all they had was a very
expensive set of those sheets with the colour rectangles, which was not what
I had in mind.  Instead, I stopped at a nearby artist supply shop and got a
pocket colour wheel used for mixing oils and water colours plus a stiff,
dead-white piece of card stock for a background.  The colour wheel has small
lettering plus a bar code, which are ideal for this little exercise.

    Now, a bit of a correction here.  My 3-element X2 teleconverter is a
Soligor, not a Sigma as I have been saying earlier.  The 7-element X2
teleconverter is a Sigma.  Our scapegoats and lackies regret the error.  :{b

    The lens used here is once again a Tokina 28-70mm RMC.  For the baseline
photo the FL is 70mm and the aperture is f:8.  For the photos with the three
teleconverters the FL is 35mm and the aperture is f:5.6.  Shutter speed is
1/500.  Focusing is done at f:3.5.

    Clarity was judged by way of an area of fairly fine text, which afforded
evaluation inevery direction on the subject plane.  Compared with the
baseline photo, the clarity with the Sigma 7-element X2 teleconverter is all
but exactly the same.  The Vivitar X2 telemacro is a close second, while the
Soligor 3-element X2 is last.

    With regard to colour, the Soligor was a bit lighter in the reds and
oranges while the Sigma and Vivitar were virtually unaltered.  Yellows,
greens, and blues were the same for all three.

    This test reaffirms my years-long impression of the 7-element Sigma, and
gives me added confidence that the Vivitar telemacro is a worthy piece of
field macro equipment.

Chris

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