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Re: [OM] Mt McKinkey (Denali) and an Infinity focus question

Subject: Re: [OM] Mt McKinkey (Denali) and an Infinity focus question
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Fri, 26 Jun 2009 06:50:24 -0400
I'm with Ralf on this one.  Trying to get a sharp image of a mountain 50 
miles away at 600mm equivalent would be difficult even with careful 
technique on a tripod let alone a moving train.  And I'm not 
particularly bothered by the focus stopping ahead of infinity.  The 
hyperfocal distance for an E1 at f/5.6 and 300mm is about 0.6 miles.  If 
you were focused at least that far out you got infinity.  You might have 
gotten better results at f/8 or even f/11 if the lens performs better 
there but by f/11 on an E1 diffraction is beginning to take a toll. 
Also shooting at f/8 of f/11 would have required a slower shutter speed 
or higher ISO and I think slower shutter would have been detrimental.

So, although I'm not surprised by the results I do see one thing that 
bothers me.  At about 40% of the image height from the bottom are two 
snow patches at extreme right and left of the image.  There seems to be 
a distinct difference in sharpness between the two with the left side 
showing more clearly defined edges.  Whether this is lens or something 
else I can't tell.  Like Ralf did, I suggest some controlled tests on a 
tripod.

Chuck Norcutt


Lawrence Woods wrote:
> I just got back from a trip to Alaska, and have been plowing 
> forward through the accumulated OM digests - am now up to June 
> 16th - but wanted to post a few pictures and ask a couple 
> questions.
> 
> These pictures were taken from a moving train when we were 
> about 50 miles from Mt. McKinley. I've fiddled with them using 
> Lightroom, which I don't really know how to use yet, going for 
> a postcard effect.
> 
> The pictures are from my E-1, ISO at 200.
> 
> 14-54 lens @ 42mm, f/7.1, 1/800 
> http://users.rcn.com/rmwoods/OM/P6150189_1K.jpg
> 
> 70-300 lens @ 70mm, f/4, 1/2500 ISO 200
> http://users.rcn.com/rmwoods/OM/P6150205_1K.jpg
> 
> 70-300 lens @ 300mm, f/5.6, 1/2500 ISO 200
> http://users.rcn.com/rmwoods/OM/P6150178_1K.jpg
> 
> And another mountain
> 14-54 lens @52mm, f/4 1/2000 -1EV
> http://users.rcn.com/rmwoods/OM/P6150209_1K.jpg
> 
> The 300mm picture is something of a disappointment in terms of 
> sharpness and contrast.  Is this just in the nature of a 600MM 
> FOV and the accumulated atmosphere between the subject and me?  
> Or would stopping down have helped? 
> 
> When both lenses autofocused, they stopped well short of the 
> infinity stop.  This was true at all focal lengths.  I tried 
> manual focusing, and the sharpest I could focus seemed to be 
> at the same point the autofocus picked.  Is this normal, or do 
> my lenses need to be recalibrated?  A 50 mile subject distance  
> ought to be infinity in my book, even for a 300mm lens.
>    
> 
> ----- Larry Woods
>       lmwoods@xxxxxxx
-- 
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