There's also more involved than just the size of the air column. In the
case of David's racing shots he's shooting with a full-frame 8 MP camera
at f/16 and panning with an 800mm lens at 1/200 second. The theoretical
diffraction limit for a full-frame sensor at f/16 is 7 MP with a perfect
lens. The lens, while good, is not perfect and so the choice of f/16 is
limiting resolution to something less than 7 MP. f/11 would likely have
been a better choice for resolution had it not been for the desire to
have a slowish shutter speed to show some motion blur. And, while he's
panning to help compensate for the slowish shutter speed, good as he
obviously is, that panning motion can't possibly be the equivalent of a
stationary lens on a rock steady tripod.
Shooter and lens delivered a pleasing result but it would be difficult
to judge the ultimate image quality of the lens based on these shooting
conditions.
Chuck Norcutt
Moose wrote:
> Dawid Loubser wrote:
>> ...
>>
>> The Tokina lens is not great - the colours suck, but it is pretty sharp, and
>> it draws beautifully (apart from the bad CA). This was from a motor racing
>> shoot, at 800mm the subject has to be MASSIVELY far away to even fit in the
>> frame without cropping it:
>>
>> http://philosomatographer.deviantart.com/art/Shelby-Daytona-60912549
>>
>> and a crop, to see the old 1960s/1970s bazookha is really not too bad in the
>> sharpness department:
>>
>> http://philosomatographer.deviantart.com/art/Shelby-Daytona-Crop-60913115
>>
>
> Much the conclusion I came to with my Tokina AT-X 150-500mm zoom. It's
> not apparently wildly sharp at the long end. On the other hand, it
> clearly resolves more detail than is available in a crop from the short
> end. <http://www.moosemystic.net/Gallery/MPhotos/BayArea/Delta/Falling.htm>
>
> Another thing to consider, assuming vibration has been controlled, is
> that many long tele shots tend to include a long column of air, dust,
> water vapor, etc., which reduces contrast and sharpness/resolution. For
> the same subject size on film, an 800mm lens will shoot through 10x the
> amount of air as an 80mm lens. I think really long lenses often get a
> bum rap for factors that aren't their fault.
>
> I really should rescan this with the 4000 dpi scanner and apply what
> I've learned in the last 2-3 years. Still, it came out rather well for a
> hurried tripod shot - no MLU/aperture pre-fire - and without the
> problems of distance. Shot at 5-6 m.
> <http://www.moosemystic.net/Gallery/MPhotos/Home/Towhee.htm>
>
> Moose
>
>> On the topic of ultra-telephoto-lenses: Have you ever seen the Tokina 800mm?
>> It's quite rare, little mention of it on the web, if you are interested,
>> this is what it looked like on my Canon Wunderbrick:
>>
>> http://philosomatographer.deviantart.com/art/Tokina-800mm-f1-8-lens-61359279
>>
>
> A monster indeed! You remind me that I haven't used the 150-500/5.6 for
> ages, mostly because of the size and weight, and it looks tiny next to
> the 800/8. With a 1.4x TC, it would be 700/8. I wonder if I ever did
> that? Probably not. Something to try someday. :-)
>
> Moose
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