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05-15-2013, 11:16 AM   #1
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Pentax FA80-320mm Lens

I recently brought the above lens second hand as a short term measure to take photos of the local cricket team. the problem is when i set my camera to take continuous photos i get no way near the 6fps i get with standard 18-55mm lenses. Could members give me any reasons for this. is it because the lens is faulty or is because its an old make and cannot transfer data to the camera quick enough.



Last edited by crlester; 05-15-2013 at 12:13 PM.
05-15-2013, 12:03 PM   #2
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You might require a flash. My best guess is that with the kit lens, you get a lot of background imagery, such as lights, resulting in a higher shutter speed. With a tighter frame, you'd underexpose with the same settings.

My recommendation would be either bump your ISO up towards 3200/6400, and proceed to set your camera to underexpose by a stop. You can batch process them to have +1 stop exposure in a program like Lightroom.

Alternatively, you can just invest in a cheap flash, or save up and buy a 70-200 2.8 from Tamron/Sigma.
05-15-2013, 12:52 PM   #3
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QuoteOriginally posted by crlester Quote
is it because the lens is faulty or is because its an old make and cannot transfer data to the camera quick enough.
Try the same type of shot at 50mm or so and see if it makes a difference. It is likely that on the long end the camera is not locking focus as fast as it would with the shorter kit lens. Some lenses seem to be faster to focus than others. I've not used that lens but I do have a FA 28-105mm that is remarkably slow to focus compared to my DA series lenses.

And it might not be anything wrong with the lens at all. Focusing at 320mm is going to be harder than focusing at 50mm because of camera shake if nothing else. See if the lens focuses quick enough at short focal lengths first. If it does then the problem is just the long length. If the problem persists even at 50mm then I would say it is the lens.
05-15-2013, 02:18 PM   #4
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The burst rate will depend on many factors. The AF can certainly be one them. The 18-55 has a lot of DOF, especially stopped down on the shorter lengths. It likely doesn't have to adjust focus at all where if you are shooting a moving subject with a long lens, it most likely does. Obviously, your shutter speed needs to be fast enough for a 6fps burst.


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