Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-19-2012, 05:57 AM   #1
New Member




Join Date: May 2012
Posts: 7
Focusing Problem with 50mm Lens, not with zoom lens

Hi there. This is a bit of a beginners problem to be honest, but I'm having trouble tracking down what the problem is here.

I recently bought a Pentax ME Super with a 50mm1.7 Lens, and a Petri 80-200mm zoom lens. I got my first set of shots back (a lot of which were mainly to test out various configurations e.g. different lenses, different flash settings etc.). However there was a problem with my shots: all the shots that I had taken on the 50mm lens were badly out of focus. A couple had areas that were almost in focus, but most were completely out. However, all the shots I took with the zoom lens came out relatively sharp and definitely in focus.

The majority of shots on the 50mm lens were indoors without a flash and so I had the aperture almost or completely wide open for most of them. Is this where I am going wrong? I'm assuming the problem isn't the camera if the shots on the zoom lens are OK? I'm thinking that the problem is most likely me but i thought in a batch of 20 shots I would've at least got one close?

Any help would be greatly appreciated!

Thanks

Tim

05-19-2012, 06:01 AM   #2
Pentaxian
Mareket's Avatar

Join Date: Jun 2011
Location: Chester
Photos: Gallery | Albums
Posts: 719
It's probably because the viewfinder can only show a DoF around an aperture of f/2.8, and the 50mm will be faster than that, so you can't truly see if it's properly in focus.
05-19-2012, 06:58 AM   #3
Veteran Member
kcobain1992's Avatar

Join Date: Dec 2010
Location: Bucharest, Romania
Photos: Gallery
Posts: 1,409
Can you post some examples of what you call "badly out of focus"?
05-19-2012, 07:58 AM   #4
New Member




Join Date: May 2012
Posts: 7
Original Poster
Focus Problems - a set on Flickr <--- This photo set has the whole roll in it, the last four (filenames zoom1-4) are the ones taken with the zoom lens. I know some are unsuccessful for other reasons but most of them show the focusing problem.

Thanks Mareket. What would you suggest to avoid the problem?

05-19-2012, 09:22 AM   #5
Veteran Member




Join Date: Jul 2009
Location: London
Posts: 857
Are you saying it looked ok when you focussed, but ended up oof?

Sorry if I'm insulting you here, but it looks like you haven't focussed them at all, and anything that is vaguely in focus is due to dof.
05-19-2012, 09:33 AM   #6
New Member




Join Date: May 2012
Posts: 7
Original Poster
Yeah pretty much. I focused a lot with the prism but I wouldn't have ignored the image as a whole. The shots look nothing like what I saw in the viewfinder. What I can't understand is why only this lens seems to do it.
05-19-2012, 09:57 AM   #7
Veteran Member




Join Date: Jul 2009
Location: London
Posts: 857
One thing that comes to mind is that the focus screen isn't seated properly. When you look through the viewfinder you're looking at an image on the focus screen. If the screen's moved, the focus on the screen may look correct but it will be out at the film plane, hence your oof shots.

Send me a pm with your email address, and I'll send you copies of a ME Super service manual and a ME Super user manual I've got.
05-19-2012, 11:54 AM   #8
New Member




Join Date: May 2012
Posts: 7
Original Poster
Would that not affect the zoom lens as well though?

Thanks, will message it now.

05-19-2012, 12:04 PM   #9
Veteran Member
kcobain1992's Avatar

Join Date: Dec 2010
Location: Bucharest, Romania
Photos: Gallery
Posts: 1,409
OK they are badly out of focus. I can't explain why, though. You are right in assuming that focusing errors should be constant regardless of lens used, but it's possible that the smaller aperture of that tele zoom (and consequently, larger DOF) masks focusing inaccuracies to an extent. It would be easier for us to tell you the exact reason if you uploaded some pictures taken with the Petri zoom as well. Otherwise, the focusing screen or the mirror are the only things that can bust your focusing precision.
You seem to have a case of back-focus (image is focused behind the point where you intended it to be). Can you tell if the camera has been previously taken apart?
05-19-2012, 12:29 PM   #10
New Member




Join Date: May 2012
Posts: 7
Original Poster
The last 4 images in that set are the ones taken with the zoom. I was told by the previous owner that it was serviced in 2007 and not used much since.
05-19-2012, 01:10 PM   #11
Veteran Member
kcobain1992's Avatar

Join Date: Dec 2010
Location: Bucharest, Romania
Photos: Gallery
Posts: 1,409
I can't judge from those. You may want to spend another film shooting a focus test chart, and if your problem is consistent with both lenses, send your camera to a repair shop.
05-21-2012, 08:13 AM   #12
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,202
QuoteOriginally posted by Mareket Quote
It's probably because the viewfinder can only show a DoF around an aperture of f/2.8, and the 50mm will be faster than that, so you can't truly see if it's properly in focus.
...This is a 35mm film camera with an old style focus screen. The DOF in the viewfinder will be the same as at the film plane for 1:1 image size (i.e. contact print).

I looked at the series on Flickr and to be honest, all look to be pretty soft with most being grossly OOF though there is a tendency to back focus (background in focus) on all examples. Here are my suggestions:
  • Do your focus test on a flat subject having fine detail and high contrast, newsprint taped to the wall is a good target.
  • Do your focus test in good light with camera on tripod (if possible)
  • Use the focus aides in the viewfinder
  • If you wear eyeglasses, have them on when focusing
  • If possible, evaluate the negative using a loupe rather than a scanned image
Possible explanations:
  • Bad scans. Focus is critical when scanning and the negative carriers for most consumer scanners do a poor job of properly positioning the negative
  • Missing or damaged film pressure plate in body
  • Body has been "serviced" and the focus screen installed upside-down or without its shims
To be very specific...it is highly unlikely that the lens is the cause of your problem. If you can attain focus and a sharp image in the viewfinder, the same should be true with the final image. That is why we use an SLR.


Steve

Last edited by stevebrot; 05-21-2012 at 08:24 AM.
05-21-2012, 01:20 PM   #13
New Member




Join Date: May 2012
Posts: 7
Original Poster
I compared my camera with a friend's fully functional ME Super, and my viewfinder seems cloudy and unclear compared to his. Even though in mine I can seem to get the image into what looks like focus, there is still a general cloudiness over the whole picture in the viewfinder.
05-21-2012, 01:27 PM   #14
Veteran Member
kcobain1992's Avatar

Join Date: Dec 2010
Location: Bucharest, Romania
Photos: Gallery
Posts: 1,409
Did you try swapping the lenses, so you could isolate the problem to the camera or the lens?
05-21-2012, 03:36 PM   #15
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,202
QuoteOriginally posted by timdoyle91 Quote
I compared my camera with a friend's fully functional ME Super, and my viewfinder seems cloudy and unclear compared to his. Even though in mine I can seem to get the image into what looks like focus, there is still a general cloudiness over the whole picture in the viewfinder.
Your viewfinder should be crystal clear and bright...like looking through a window. The ME Super was known for its excellent viewfinder (one of the best ever made) and images should snap into focus.

Possible causes:
  • Focus screen installed upside down
  • Crazed or fogged focus screen due to exposure to solvents or superglue vapors
  • Wrong ocular (highly unlikely)
  • Focus screen and/or prism surfaces badly fouled by fungus



Steve
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!
50mm, flash, focus, lens, pentax help, shots
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problem getting started with new zoom lens nhughes Troubleshooting and Beginner Help 2 04-21-2011 10:47 AM
Focusing problem: K10D, screen, lens or me? jeztastic Troubleshooting and Beginner Help 6 04-08-2011 05:28 PM
Is this a front focusing camera problem or lens problem? Lens tests Metalwizards Pentax K-r 15 03-06-2011 01:24 AM
problem with m 50mm 1.7 lens tlmathena Troubleshooting and Beginner Help 11 12-10-2010 07:40 PM



All times are GMT -7. The time now is 10:37 PM. | 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