Re: Pentax A-35-105/3.5 Zoom Focusing Question
For my money, this holding of focus while zooming out is how zooms are supposed to work. Vivitar made some good lenses that were 'Vara-focal' and not true zooms that maintain focus as you zoomed. I understood that relaxing that requirement was what let them get better performance. Regards, Bob S. [EMAIL PROTECTED] writes: > This is an excellent zoom lens and the focus does track very well through the zoom >range. > Since the aperture remains constant through the zoom range, depth of field >diminishes as > you zoom in from 35 to 105 mm. The narrow DOF makes critical focus easier. At 35 mm, >the > DOF is wide and critical focus is more difficult, but it usually doesn't matter as >much > because the DOF is very wide (compared to DOF at 105 mm). What I'm saying is that the > focus doesn't change when you focus at 35 or 50 mm and zoom in to 105mm. I'm just >saying > critical focus acceptable at 50 mm is easier done at 105mm > because of the narrower DOF. > The SMCA 70-210 f/4 is the same way. - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: Pentax A-35-105/3.5 Zoom Focusing Question - THANKS BOB !!
Ok.. NOW I get it :-) Thanks for the explanation Bob.. Cheers, Dave Original Message: - From: Bob Blakely [EMAIL PROTECTED] Date: Tue, 30 Jul 2002 09:47:47 -0700 To: [EMAIL PROTECTED] Subject: Re: Pentax A-35-105/3.5 Zoom Focusing Question This is an excellent zoom lens and the focus does track very well through the zoom range. Since the aperture remains constant through the zoom range, depth of field diminishes as you zoom in from 35 to 105 mm. The narrow DOF makes critical focus easier. At 35 mm, the DOF is wide and critical focus is more difficult, but it usually doesn't matter as much because the DOF is very wide (compared to DOF at 105 mm). What I'm saying is that the focus doesn't change when you focus at 35 or 50 mm and zoom in to 105mm. I'm just saying critical focus acceptable at 50 mm is easier done at 105mm because of the narrower DOF. The SMCA 70-210 f/4 is the same way. Regards, Bob... --- "In the carboniferous epoch we were promised perpetual peace. They swore if we gave up our weapons that the wars of the tribes would cease. But when we disarmed they sold us, and delivered us, bound, to our foe. And the gods of the copybook headings said, 'Stick to the devil you know.' " mail2web - Check your email from the web at http://mail2web.com/ . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: Pentax A-35-105/3.5 Zoom Focusing Question
This is an excellent zoom lens and the focus does track very well through the zoom range. Since the aperture remains constant through the zoom range, depth of field diminishes as you zoom in from 35 to 105 mm. The narrow DOF makes critical focus easier. At 35 mm, the DOF is wide and critical focus is more difficult, but it usually doesn't matter as much because the DOF is very wide (compared to DOF at 105 mm). What I'm saying is that the focus doesn't change when you focus at 35 or 50 mm and zoom in to 105mm. I'm just saying critical focus acceptable at 50 mm is easier done at 105mm because of the narrower DOF. The SMCA 70-210 f/4 is the same way. Regards, Bob... --- "In the carboniferous epoch we were promised perpetual peace. They swore if we gave up our weapons that the wars of the tribes would cease. But when we disarmed they sold us, and delivered us, bound, to our foe. And the gods of the copybook headings said, 'Stick to the devil you know.' " --Rudyard Kipling From: "Frank Knapik" <[EMAIL PROTECTED]> > Hello. I find that this zoom focuses better when I zoom the lens out to 105, focus, >then zoom wide. It always stays in focus. I find that if I focus lets say at 50mm then zoom out to 100mm, I have to refocus. Has anyone else experienced this? I do find this lens to be a very sharp zoom. I took it to NYC on my LX, mostly using a tripod, and was very impressed with the results. Thank you. - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
RE: Pentax A-35-105/3.5 Zoom Focusing Question
Francis, I too have noticed the same thing - seems to focus just fine at 105 and then zoom out. Try it the other way around and it's "time to refocus". I thought this was just me but obviously there are at least 2 of us who have this little concern. It's not a big deal really but I guess this is due to the fact that it's a 2 touch zoom rather than a "standard" zoom. Any other inputs would be helpful Dave Original Message: - From: Frank Knapik [EMAIL PROTECTED] Date: Tue, 30 Jul 2002 12:01:49 -0400 To: [EMAIL PROTECTED] Subject: Pentax A-35-105/3.5 Zoom Focusing Question Hello. I find that this zoom focuses better when I zoom the lens out to 105, focus, then zoom wide. It always stays in focus. I find that if I focus lets say at 50mm then zoom out to 100mm, I have to refocus. Has anyone else experienced this? I do find this lens to be a very sharp zoom. I took it to NYC on my LX, mostly using a tripod, and was very impressed with the results. Thank you. Francis mail2web - Check your email from the web at http://mail2web.com/ . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: Pentax A-35-105/3.5 Zoom Focusing Question
That's true of most zooms. At 12:01 PM 7/30/2002 -0400, you wrote: >Hello. I find that this zoom focuses better when I zoom the lens out to >105, focus, then zoom wide. It always stays in focus. I find that if I >focus lets say at 50mm then zoom out to 100mm, I have to refocus. Has >anyone else experienced this? I do find this lens to be a very sharp zoom. >I took it to NYC on my LX, mostly using a tripod, and was very impressed >with the results. Thank you. > >Francis >- >This message is from the Pentax-Discuss Mail List. To unsubscribe, >go to http://www.pdml.net and follow the directions. Don't forget to >visit the Pentax Users' Gallery at http://pug.komkon.org . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Pentax A-35-105/3.5 Zoom Focusing Question
Hello. I find that this zoom focuses better when I zoom the lens out to 105, focus, then zoom wide. It always stays in focus. I find that if I focus lets say at 50mm then zoom out to 100mm, I have to refocus. Has anyone else experienced this? I do find this lens to be a very sharp zoom. I took it to NYC on my LX, mostly using a tripod, and was very impressed with the results. Thank you. Francis - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
