Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-29-2013, 12:26 PM   #1
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Pentax A 70-210mm is blurry at infinity at 210mm

It is sharp closer in and at shorter focal lengths but at the long end and at infinity it is unusable. Anyone else see this? Is it worth sending back to Pentax for recalibration?

06-29-2013, 12:32 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,944
QuoteOriginally posted by Rob22315 Quote
It is sharp closer in and at shorter focal lengths but at the long end and at infinity it is unusable. Anyone else see this? Is it worth sending back to Pentax for recalibration?
It shouldn't be blurry, but does your focusing ring turn past the infinity part? The true point of infinity focus may be before or after the mark on the ring, depending on the ambient temperature.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-29-2013, 06:02 PM   #3
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
QuoteOriginally posted by Adam Quote
It shouldn't be blurry, but does your focusing ring turn past the infinity part? The true point of infinity focus may be before or after the mark on the ring, depending on the ambient temperature.
I tried taking photos with objects at a variety of distances believing that something should being focus but nothing was. I also tried focussing shorter than infinity and still nothing was in focus. At shorter distances - around 20-30 feet, the lenses did great. Beyond that, mush.
06-30-2013, 05:47 AM   #4
Site Supporter
p38arover's Avatar

Join Date: Mar 2012
Location: Western Sydney, Australia
Photos: Gallery | Albums
Posts: 3,000
Is this in MF or AF mode?

06-30-2013, 07:06 AM   #5
MSL
Pentaxian
MSL's Avatar

Join Date: Feb 2012
Location: Greater Toronto Area
Photos: Albums
Posts: 3,359
It is a MF lens.
Any chance of posting samples of roughly the same scene with minor adjustments to the focus distance, and telling us what aperture you used.
06-30-2013, 08:44 AM   #6
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,134
QuoteOriginally posted by Rob22315 Quote
It is sharp closer in and at shorter focal lengths but at the long end and at infinity it is unusable. Anyone else see this? Is it worth sending back to Pentax for recalibration?
I owned a 70-210 for many years on my film cameras, and now my daughter is using it on her K200d, and it has always been sharp for both of us.
06-30-2013, 09:19 AM   #7
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
Thanks all for posting. I'll post some samples within a day. This lens has a good reputation so it's possible I got a bad copy or it's operator error.
06-30-2013, 03:45 PM   #8
Site Supporter
p38arover's Avatar

Join Date: Mar 2012
Location: Western Sydney, Australia
Photos: Gallery | Albums
Posts: 3,000
QuoteOriginally posted by MSL Quote
It is a MF lens.
Oops! Silly me. I read it as Pentax F 70-210 (I have one), not Pentax A......

07-01-2013, 05:58 AM   #9
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
After reading through the replies last night, I took the camera/lens and slapped it on a tripod to shoot some photos around the neighborhood. The photos were fine (I'll post the results tonight), even out almost to infinity. Zooming in 16x and the detail was good, much better than on Saturday.

One of the problems with Saturday morning's shoot is that I was judging distance by the focus ring which basically shows 15 ft, then infinity (or perhaps it's 15 meters !?#$%). There's still ample throw in the focus ring beyond 15 ft - I was shooting around the neighborhood at distances much greater than 15 ft (or meters) and still not bottoming out the focus ring.
07-01-2013, 06:06 AM   #10
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
An important aspect is where do you set your Shake Reduction? This setting will determine some aspect of sharpness and when using on a tripod, SR should be turned off...

FWIW - I don't have the A 70-210 but do have the F 70-210 and I needed to reset the focus at infinity. The lens could focus accurately on most distances but never infinity...
07-01-2013, 10:42 AM   #11
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
QuoteOriginally posted by theunartist Quote
An important aspect is where do you set your Shake Reduction? This setting will determine some aspect of sharpness and when using on a tripod, SR should be turned off...

FWIW - I don't have the A 70-210 but do have the F 70-210 and I needed to reset the focus at infinity. The lens could focus accurately on most distances but never infinity...
I turned SR off when I put the camera on the tripod last night. I tried SR on and off when I was shooting handheld on Saturday morning. I also tried a variety of SR settings (some less than 200, some at 200, some longer than 200) but didn't see much difference in the results. The length of the A 70-210 doesn't change when zooming and the forward-most element is quite a ways from the camera so I wasn't sure if setting the SR to the actual focal length was proper. Besides, I don't want to have to reset the SR every time I zoom. I also tried it handheld with the SR off.

Maybe I simply need to resign to using this lens with a tripod or monopod.

How did you reset the focus at infinity?
07-11-2013, 02:19 PM   #12
Veteran Member




Join Date: Oct 2010
Location: Baltimore
Posts: 2,542
QuoteOriginally posted by Rob22315 Quote
I turned SR off when I put the camera on the tripod last night. I tried SR on and off when I was shooting handheld on Saturday morning. I also tried a variety of SR settings (some less than 200, some at 200, some longer than 200) but didn't see much difference in the results. The length of the A 70-210 doesn't change when zooming and the forward-most element is quite a ways from the camera so I wasn't sure if setting the SR to the actual focal length was proper. Besides, I don't want to have to reset the SR every time I zoom. I also tried it handheld with the SR off.

Maybe I simply need to resign to using this lens with a tripod or monopod.

How did you reset the focus at infinity?
I would not know how to set infinity on your A 70-210 and you should be able to use it handheld rather easily.

In regards about the Shake Reduction setting, I believe it will make a difference. Awhile back, I was out trying a new Super Tak 35/3.5, took plenty of photos that looked good but when I uploaded, almost all but one was slightly out of focus. I blamed the lens and then my aging K10 but when I looked more closely, I realized I set SR to 120mm instead of 35mm!

Here is the photo and you can read my ongoing comments:



This is an image with correct SR set, same lens:



As far as what setting to use for a zoom, this has been discussed many many times here at PF. Personally, I have 2 Pentax-A zooms I predominately use, the 24-50 and 35-105. I set each at the lowest setting, 24mm and 35mm, and generally has worked well for me. You should check your lens for possible haze etc., take a flashlight and shine through lens either from rear or front, it should be nicely clear, if it looks a bit dirty or foggy, it maybe hazed. But don't forget manual focusing is something that needs to be practiced, alot

Link to a discussion re: SR settings: https://www.pentaxforums.com/forums/pentax-beginners-corner-q/183199-shake-re...al-length.html
07-14-2013, 04:34 PM   #13
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
Thanks all!!

Here are two shots I took in my neighborhood on a tripod along with 100% crops. Looks to me like it's my inability to handhold this lens rather than a bad lens.
Attached Images
       
07-15-2013, 01:04 AM - 1 Like   #14
Veteran Member




Join Date: Jan 2010
Location: Southern England
Posts: 495
If you don't want to keep redefining focal length for best SR effectiveness, you can use the formula 2*min*max/(min+max) for a compromise value. For the 70-210 lens this means you should choose the "100mm" option.

You can now shoot with confidence that you'll always be getting some SR effectiveness, whatever focal length you choose. Worst effectiveness is obviously at the extremes (i.e. the min and max focal lengths), but if memory serves me, even in these situations, you'll be getting 1 stop's worth of SR.

If you do decide to try to match the value to the actual focal length you're shooting at, be careful that you don't forget to change it when you change your zoom setting for subsequent shots. Because if your value is more than 2x the actual focal length you're shooting at, you'll get more blur than if you had SR switched off. And for values a lot greater than 2x the actual focal length, you'll get a lot more blur!
07-15-2013, 11:55 AM   #15
Veteran Member




Join Date: Mar 2007
Location: Alexandria VA USA
Posts: 315
Original Poster
QuoteOriginally posted by m42man Quote
If you don't want to keep redefining focal length for best SR effectiveness, you can use the formula 2*min*max/(min+max) for a compromise value. For the 70-210 lens this means you should choose the "100mm" option.

You can now shoot with confidence that you'll always be getting some SR effectiveness, whatever focal length you choose. Worst effectiveness is obviously at the extremes (i.e. the min and max focal lengths), but if memory serves me, even in these situations, you'll be getting 1 stop's worth of SR.

If you do decide to try to match the value to the actual focal length you're shooting at, be careful that you don't forget to change it when you change your zoom setting for subsequent shots. Because if your value is more than 2x the actual focal length you're shooting at, you'll get more blur than if you had SR switched off. And for values a lot greater than 2x the actual focal length, you'll get a lot more blur!
Excellent tip, I'll give it a shot. I can say I didn't try 100mm in the SR setting.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
infinity, k-mount, pentax, pentax a 70-210mm, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
RMC Tokina 70-210mm F3.5 is the same as Tokina Vivitar Series I 70-210mm ? minahasa Pentax SLR Lens Discussion 11 09-17-2011 09:59 AM
For Sale - Sold: Pentax SMC-A 70-210mm f4 Macro zoom; Pentax A3000 film SLR; Vivitar 28-210mm z NeverSatisfied Sold Items 9 05-14-2010 01:37 PM
Pentax A 70-210mm vs Vivitar S1 70-210mm Zeeke Pentax SLR Lens Discussion 11 04-24-2010 07:57 AM
Compare the lens coating of Takumar-F 70-210mm and smc Pentax-F 70-210mm jcdog2006 Pentax SLR Lens Discussion 13 02-19-2010 08:16 AM



All times are GMT -7. The time now is 01:51 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top