Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-29-2011, 02:00 PM   #1
New Member




Join Date: Sep 2011
Posts: 21
Expecting too much from my Sigma 17-50mm?

With my K-x, I took a picture about 9ft away - 1/6 at 2.8, ISO 200, 50mm just to test the sharpness.

I consider myself a newb so I guess I am expecting too much in terms of quality but I was hoping to see a pretty sharp image.

Experts?




10-29-2011, 02:06 PM   #2
Veteran Member




Join Date: Apr 2011
Location: San Diego
Photos: Gallery
Posts: 883
try shooting at a higher shutter speed, 1/6s is really slow and is bound to induce a little bit of hand shake/motion blur
10-29-2011, 02:08 PM   #3
New Member




Join Date: Sep 2011
Posts: 21
Original Poster
I used my remote so that should minimise shake.
10-29-2011, 02:08 PM   #4
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
The image is soft because 1) the shutter speed is too slow for hand-held shot or 2) there is a front-focus error on the lens (needs micro-adjustment). I suspect that you could at least try 1/60 shutter speed using higher iso setting.

10-29-2011, 02:15 PM   #5
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
When testing the optical properties of your lens, be sure to focus manually to eliminate any possible problem due to AF.
10-29-2011, 02:22 PM   #6
Veteran Member




Join Date: Jul 2010
Location: Flushing NY
Photos: Albums
Posts: 412
Did you hand-hold it, or use a tripod? Looks pretty good at that shutter speed if you were holding it. At the wide end of the zoom, the SR would have handled that, I'm sure. But at 50mm? No way.
10-29-2011, 02:36 PM   #7
Inactive Account




Join Date: Jul 2010
Photos: Gallery
Posts: 328
Hi

Problem is the f2.8, too much hype about " Wide Open " shots !
It is simple physics of lenses, they will only show their best properties in the Mid range. Usually starting at 2 Stops down.
The reasoning behind Fast lenses is the stopped down point will be still faster than slower lenses Full open.
Try the shot at f4 or f5.6, it will also end the focus problems.
10-29-2011, 02:40 PM   #8
New Member




Join Date: Sep 2011
Posts: 21
Original Poster
I was using a tripod with the remote.

Is there any way to remedy front-focus error or is it inherint in lenses?

The testing continues...

10-29-2011, 02:42 PM   #9
Veteran Member




Join Date: Apr 2011
Location: San Diego
Photos: Gallery
Posts: 883
access debug mode in your k-x, from there you should be able to do a global AF adjustment. Just remember to set it back once you swap lenses
10-29-2011, 05:24 PM   #10
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
QuoteOriginally posted by Noggin Quote
I was using a tripod with the remote.

Is there any way to remedy front-focus error or is it inherint in lenses?

The testing continues...
So you used the remote to activate the focusing mechanism? This method does not warrant that the camera focuses correctly, especially in dim light.
10-29-2011, 05:25 PM   #11
Veteran Member
causey's Avatar

Join Date: Feb 2009
Location: Arlington, VA
Photos: Albums
Posts: 3,758
QuoteOriginally posted by Noggin Quote
I was using a tripod with the remote.

Is there any way to remedy front-focus error or is it inherint in lenses?

The testing continues...
Don't jump to conclusions. You don't know whether the lens front-focuses. You haven't identified the root of the problem. It might be your testing procedure.
10-29-2011, 09:15 PM   #12
Junior Member




Join Date: Jan 2011
Photos: Gallery
Posts: 27
Is that a 100% crop? If you're expecting any lens to look sharp wide open at 100%, then yes, you are expecting too much especially handheld at 1/6!
10-30-2011, 04:51 PM   #13
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
If that was taken at 9ft and 50mm, then it is apparently a crop. You haven't explained how you, the photographer, controlled where exactly focus was achieved; it's fr to early to even think about blaming the equipment for anything. But for a crop taken of an image taken at f/2.8 at a very slow shutter speed (even with tripod), given the shallow DOF, that's probably not too far off what you should be expecting even if you did in fact take the necessary steps to guarantee focus was where you wanted it.
10-30-2011, 07:23 PM   #14
New Member




Join Date: Sep 2011
Posts: 21
Original Poster
Yes its a 100% crop. Im not really blaming anything more than getting a reality check on what to expect

I used the remote in focus mode I think tho I did a focus from that camera first anyway.

I appreciate the feedback a lot!
10-31-2011, 08:30 PM   #15
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Right, but which focus point did you select, and are you sure the subject completely covered the focus point? From the crop, it sure appears possible focus was on the amp, not the bass.
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!
k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Focus Question - Camera, Lenses or Expecting Too Much? mtngal Pentax K-5 11 02-15-2011 03:00 AM
Am I expecting too much? FHPhotographer Pentax DSLR Discussion 59 01-11-2011 07:50 PM
Out Of Focus - Am I expecting too much? seachunk2 Troubleshooting and Beginner Help 28 03-02-2010 03:27 PM
Am I expecting too much out of an old lens? whelmed Troubleshooting and Beginner Help 11 02-11-2010 07:10 PM
I'm Expecting! magnum1 Welcomes and Introductions 4 10-10-2007 08:10 PM



All times are GMT -7. The time now is 08:31 PM. | See also: NikonForums.com, CanonForums.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