Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-13-2011, 08:01 AM   #1
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Sigma lenses and Pentax body marriage

Hello guys. I really hope someone can help. The thing is that from times to time, I think of changing the system. All of that because of some problems that I always have with my camera and lenses that I have. Here, in Moldova, where I live, are not so many Pentax users, that is why I am alone in my problem and can't compare what am I doing with my camera (maybe I am ndoing something wrong?). I have a Pentax k20D body, and 4 Sigma lenses: 50mm F1.4 EX DG HSM, 10-20mm F3.5 EX DC HSM, 24-70mm F2.8 EX DG Macro and 70-200mm F2.8 EX DG APOMacro HSM II. All lenses with 2 Hoya Pro1 Digital MC Uv(0) and Marumi MC-UV filters. So, the problem is that I almost always have kind of blurred images. The images are not 100 sharp. Previously I had a Pentax k10D body. I have changed it to K20D. The same problem. Even if I photograph a person from 5 meters, on a tripod, mirror lock-up, shake reduction OFF - the sharpness of the picture is not what i think it should be. I take off the UV filter - the same thing. I heard that Sigma lenses need professional adjustment with the used body. Right? Should I do that? From another point of view there is a camera function that permits that adjustment. Right. But the thing is, that the camera should recognize the lense, there should appear a serial number, ID, or something like that, because some lenses have front focus, some back focus. This is why the camera have to recognize the lense to apply adjustments personally for each lense. Well, the camera seems to make no difference between my wide-angle zoom, standard zoom, standard prime and telephoto lenses.
OOOOO, that's a long speech! ;-) Does anyone knows the solution for this problem? By the way, I think and my wife confirms that my hands are totally OK.

05-13-2011, 08:14 AM   #2
Senior Member
metalmania's Avatar

Join Date: Feb 2011
Posts: 253
Did you try K20D AF calibration?
05-13-2011, 08:25 AM   #3
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
I'd start by posting some sample images that demonstrate the problem. It's possible your expectations are simply too high. I'm assuming you are familiar with the concept of DOF and aren't looking for sharpness outside the plane of focus.
05-13-2011, 08:31 AM   #4
Senior Member




Join Date: May 2009
Location: Edmonton, AB
Posts: 246
There are few possibilities: dirty lens, dirty sensor, or camera AF needs calibration. Of course you know all that. All the lenses you have are very good and sharp according to many reviews out there. IMHO maybe your expectation is too high (to much pixel peeping?) or you are not shooting at the optimum focal/aperture for sharpness.

Respectfully,

Peter

05-13-2011, 09:01 AM   #5
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Original Poster
puctures

I bought my lenses after reading a lot of reviews. Lenses and sensor are clean. I attach a picture. The focus was in the center of the red circle. I was only testing the autofocus. ISO 100, f4, 1/80sec on tripod. My wife wasn't moving. According Hyperfocal Distance and Depth of Field Calculator - DOFMaster, at 165mm focal length, at 5-6 m, a should have about 14-21cm depth of field. I think all the settings are quite OK for tripod shot. But, I see no front or back focus. The picture is only out of focus.
Attached Images
     
05-13-2011, 09:32 AM   #6
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Original Poster
Is there a ONLY camera AF calibration? I thought there is only a camera calibration with a lense attached. Anyway, how do I perform a camera AF calibration?
05-13-2011, 09:47 AM   #7
Veteran Member




Join Date: Mar 2010
Photos: Gallery | Albums
Posts: 1,545
That looks like it's got a FF problem. Dial in some AF compensation and you should be fine (hopefully).
05-13-2011, 09:55 AM   #8
Site Supporter




Join Date: Mar 2011
Location: DENVER
Posts: 84
Have you tried manually focussing the lenses; are results the same or better?

05-13-2011, 10:03 AM   #9
Senior Member
metalmania's Avatar

Join Date: Feb 2011
Posts: 253
I calibrated my K10D before. It's based on one lens but the result is good for all lenses I have. I don't know about K20D.
05-13-2011, 11:30 AM   #10
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Original Poster
Thank You guys. Well, I have done some tests, but I realized that each lens needs different AF compensation for best results. As You understand a 70-200mm lens will need different AF compensation as a 10-20mm lens. Taking something in between? I am not used with Nikon and Canon, but I am almost sure that they don't have that problems. Am I wrong?
And should the camera recognize some how the lens? Should there appear a serial number, ID, or something like that? How does the camera recognize the lens if I do an AF compensation for ONE lens and not for all?
05-13-2011, 11:46 AM   #11
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Original Poster
AF adjustment -> Apply One -> The lens ID is displayed when obtained. Saves and applies an adjustment value for each lens type. GOOD! What if the lens ID is not obtained? Will the K20D still remember the different settings for each lens?
05-13-2011, 11:58 AM   #12
Forum Member




Join Date: Mar 2011
Location: Maryland
Photos: Gallery
Posts: 81
QuoteOriginally posted by marinb Quote
I am not used with Nikon and Canon, but I am almost sure that they don't have that problems. Am I wrong?
When it comes to 3rd party lens, it's the same. Sometimes, even C/N oem lenses have FF/BF problems.

QuoteOriginally posted by marinb Quote
AF adjustment -> Apply One -> The lens ID is displayed when obtained. Saves and applies an adjustment value for each lens type. GOOD! What if the lens ID is not obtained? Will the K20D still remember the different settings for each lens?
The lens you mentioned should all have lens ID.
05-13-2011, 12:13 PM   #13
Forum Member




Join Date: Jan 2010
Location: Chisinau
Posts: 51
Original Poster
I am sure all that lenses should have ID. So, the camera don't read/recognize the ID or only don't display that ID?.
05-13-2011, 01:11 PM   #14
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by marinb Quote
According Hyperfocal Distance and Depth of Field Calculator - DOFMaster, at 165mm focal length, at 5-6 m, a should have about 14-21cm depth of field.
Yes - meaning that at typical print sizes viewed from a typical distance, the results should be acceptably sharp to most people within that rang. But you're talking about pixel peeping at 100% - that's another matter entirely. It'd start by dividing the ordinary DOF by 10 to get a rough guess as to how much will appear criticially sharp when viewed at 100%.

QuoteQuote:
But, I see no front or back focus. The picture is only out of focus.
If it's truly "out of focus", then something else should be *in focus*, meaning it *is* BF or FF. I think what you mean to say here is that is simply *soft*. as in focus as it can be, but soft.

However, I don't think you can rule out FF or BB here, since there is nothing directly in front of or behind the subject to compare. The grass in front of the subject does *possibly* seem like it might be more in focus than the grass at her feet, but it's hard to tell, and in any event, given the field curvature you'd expect of any lens but a macro prime, the focus plane toward the edge of the frame *should* be front of the focus plane at the center of the frame.

Anyhow, if you want to test focus, that's why focus test charts were invented - to create a test in which you can actually see if your camera/lens has FF or BF. Even these aren't foolproof because of field curvature issues, but you would definitely need a *much* better controlled test than this to be able to say what might be going on in terms of focus.

But no question, that's softer than I'd expect for f/4 on an f/2.8 zoom. Assuming it's not FF or BF, I'd first wonder how sturdy was your tripod, if you used the 2-second timer, and if not, if you at least turned off SR. You mentioned you did these things on earlier tests, but I just thought I'd be sure.
05-13-2011, 08:02 PM   #15
New Member
dickymastelero's Avatar

Join Date: Mar 2011
Location: Edmonton, Alberta CANADA
Photos: Albums
Posts: 16
Been using Sigma, Tamron and variety of Pentax lenses in my K20D, from Prime to Zoom lens including Macros and fisheyes. Every lens I have been individually set at my cameras AF adjustment (apply one setting). Aftermarket lenses have their own ID's that the K20D remembers every time you install it (this ID's doesn't show in exif also), once you set it in the camera your setting shouldn't change. Adjusting the FF and BF is very tricky, my Sigma lens is set always on the negative adjustments.

Please check this link AF adjustment test chart to help with the Pentax K20D Custom Setting No.34 - Digital Cameras - Zimbio
I've used this charts and find it very helpful, it gets you close to where you want your focus to be. Focusing is a preference, a lot or most of the lenses are softer wide open and sharper after 2 stops down, you cannot expect everything in your lens to be sharp. THERE IS NO PERFECT LENS, EVEN THE ONE THEY HAVE ON SATTELITES.

Be patient in doing your AF adjustments and take notes of your adjustment as well in case you erase it. Hope this helps.
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!
body, camera, dg, hsm, lense, lenses, pentax, pentax body, pentax help, sigma, sigma lenses
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax 67 body and lenses don't / won't match jan normandale Pentax Medium Format 17 06-29-2016 08:06 AM
pentax lenses on a canon body...? clark Pentax SLR Lens Discussion 26 01-22-2011 03:09 PM
For Sale - Sold: Pentax K20D body, two lenses. f4ding Sold Items 9 01-28-2010 05:28 PM
Best of both worlds....Pentax body w/3yr warranty + Sigma EX Lenses with 4yr warranty brecklundin Pentax DSLR Discussion 13 08-10-2009 08:28 AM



All times are GMT -7. The time now is 03:15 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