Pentax-A 645 80-160mm

Halco · 04-29-2010, 04:16 PM

I've shot a few rolls using this lens exclusively, and seem to have arrived at a bit of a problem. In the short half of the range I can get consistently sharp images, but from that to the long end I just can't seem to pull off something as sharp as the short end. (Or even decent for that matter.)

I'm not sure if I just I can't nail the focus, or if its a lens issue. Anyone have similar problems?
Thanks

andycogbill · 04-30-2010, 06:41 AM

At the risk of stating the obvious, it could be a shutter speed issue. How are the shots on a tripod?

Halco · 04-30-2010, 09:10 AM

I shoot only on a tripod nothing slower than 1/250 sec.

Halco · 05-14-2010, 01:05 PM

I seem to be getting good results with a new focusing technique, however the zoom seems to expose differently at different focal lengths. For example, at 80mm exposure is perfect, 135 and above, its over by 1/3-0.5 of a stop. I've tried it on two different 645 bodies and it seems to be a lens issue. Any ideas? Contacts?

Matus · 05-14-2010, 03:21 PM

I have no experience with this lens, but your exposure problem sounds like problem with the aperture not being stopped down as it should during the exposure. Do you see this problem also when shooting wide open (no stopping down the lens)?

Cleaning the contact can not harm for sure ...

Halco · 05-14-2010, 07:35 PM

I'm not sure, I try not to use it wide open if possible. It seems strange that it never occurs at 80mm though. Some shots are alright, but other times they're obviously blown out.

04-29-2010, 04:16 PM	#1
Halco Senior Member Join Date: Aug 2009 Posts: 128	Pentax-A 645 80-160mm I've shot a few rolls using this lens exclusively, and seem to have arrived at a bit of a problem. In the short half of the range I can get consistently sharp images, but from that to the long end I just can't seem to pull off something as sharp as the short end. (Or even decent for that matter.) I'm not sure if I just I can't nail the focus, or if its a lens issue. Anyone have similar problems? Thanks

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04-30-2010, 06:41 AM	#2
andycogbill Forum Member Join Date: Dec 2009 Location: New York, NY Posts: 74	At the risk of stating the obvious, it could be a shutter speed issue. How are the shots on a tripod?

04-30-2010, 09:10 AM	#3
Halco Senior Member Join Date: Aug 2009 Posts: 128 Original Poster	I shoot only on a tripod nothing slower than 1/250 sec.

05-14-2010, 01:05 PM	#4
Halco Senior Member Join Date: Aug 2009 Posts: 128 Original Poster	I seem to be getting good results with a new focusing technique, however the zoom seems to expose differently at different focal lengths. For example, at 80mm exposure is perfect, 135 and above, its over by 1/3-0.5 of a stop. I've tried it on two different 645 bodies and it seems to be a lens issue. Any ideas? Contacts?

05-14-2010, 03:21 PM	#5
Matus Junior Member Join Date: Apr 2010 Location: Germany Posts: 27	I have no experience with this lens, but your exposure problem sounds like problem with the aperture not being stopped down as it should during the exposure. Do you see this problem also when shooting wide open (no stopping down the lens)? Cleaning the contact can not harm for sure ...

05-14-2010, 07:35 PM	#6
Halco Senior Member Join Date: Aug 2009 Posts: 128 Original Poster	I'm not sure, I try not to use it wide open if possible. It seems strange that it never occurs at 80mm though. Some shots are alright, but other times they're obviously blown out.