Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-12-2014, 08:42 PM   #1
Junior Member




Join Date: Mar 2014
Posts: 29
Focus problems K10D with Tokina 70-210 AF

I seem unable to get sharp focus with a Tokina 70-210 even though it's on AF with K10D's Shake reduction on. It had given me excellent photos on the Pentax SFXN I originally bought it for (years ago). It seemed pretty basic and simple then and the K10D is an effort to get my lenses back into use.The .pdf manual is incredibly difficult to track down info in and is not editable which would make the camera more useable.
I guess I'm missing some pretty basic point here. Can anyone get me going?

08-15-2014, 09:05 PM   #2
Loyal Site Supporter




Join Date: Jan 2008
Location: Virginia, USA
Photos: Albums
Posts: 232
Mike,

I don't have your exact lens, but I do have a Tokina 80-200/2.8 ATX-Pro that basically does the same thing. On an autofocus film camera (Z-1, PZ-1P, MZ-S) it is sharp as a tack and nails focus almost every time, but on my K10 & K20, 9 out of 10 shots come out blurry. I checked the focus alignment and on both cameras and it was back focusing pretty bad (more so on the K20 than the K10) but on the K20 I could adjust the focus. Even with the focus adjusted and the focus point locked in on the middle point, it still misses focus 25% of the time. I sent it into to Tokina several years ago and they told me that the lens was fine, it was just designed for film cameras, not digital. That may be the case, but I own quite a few 'film' lenses and that is the only lens that focuses that bad on digital. Another issue could be that the focus system on the K10 and K20 is not the best in the world (my PZ cameras focus faster and more accurately and they are nearly 20 years old with a supposedly inferior focus system) I have heard from a friend that the 80-200 focuses much better on the K3 due to a much improved focus system, so hopefully my issue will be resolved here in about another month.

BTW a quick way to check to see if it is the focus point or just a blurry lens or faulty camera is to take a news paper and lay it on the floor or a table. With your camera preferably on a tripod (but you could do it hand held) aim at the newspaper from about a 45 degree (or less) angle. Focus on a set point around the middle of the paper and shoot. Look at the resulting photo, if nothing is in focus I would guess that there is something either wrong with the focus system on your camera or the lens itself. If any part of the paper IS in focus then this will show where your lens is focusing in relation to where the focus system is aimed at.

Good luck,

Steve
08-15-2014, 10:10 PM   #3
Veteran Member
Imageman's Avatar

Join Date: Dec 2013
Photos: Albums
Posts: 461
I cant be sure because I have no information, but


It does not matter if your AF is working perfectly, if you have poor technique, your technique will make the images soft.


Shake reduction does not make sharp images, it makes blurry images. I know this sounds weird but its true.


It is a shake reduction system not a shake removal system, so it still allows shake its just less shake, if you want to get rid of shake altogether you have to abandon shake reduction, theres only 2 ways to make sharp images.


1 use a tripod and turn shake reduction OFF if you have shake reduction ON the shake reduction will make the images blurry.


OR


2 use traditional steady good taking practice, use a shutter speed fast enough, support the camera, brace yourself, stop breathing as you squeeze the shutter. I recommend shake reduction off when using good technique.


Use shake reduction when it is impossible to use good technique (if you have to use too slow a shutter speed for example)


If you use 100mm focal length, that's equivalent of 150mm on FF so you must use at least 1/200th


If you use 210mm focal length that's equivalent to 320mm so you must use at least 1/400th


If you have fast moving subjects you have to go faster, 1/2000th or more if the subject is a bird in flight or your moving quick or panning fast.


Are you using too small an aperture, smaller than f8 that will make images soft and unsharp.


Once you have good technique then you can look at what the camera is doing.
08-16-2014, 10:21 AM   #4
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,187
It has been my experience that lenses that worked just fine for film often appear to fall short when used on a digital camera. After all, how often do we examine a 35mm negative with an 8x loupe to evaluate sharpness? It may be that your Tokina's performance on your K10D is about the same as on your film cam.

A few things to consider before doing anything drastic:
  • How is the K10D's AF performance with other AF lenses?
  • Is the Tokina sharp when manually focused? Do "best of five" attempts using the optical viewfinder only.
  • Use a tripod when doing your evaluations, SR turned off. The two second delay timer is the easiest way to do this.
  • Evaluate using a flat high-detail target parallel to the sensor
  • Is focus locked (beep and green hexagon in viewfinder) at time of exposure?
  • Center point vs. letting the camera choose the point of focus. The K10D has more focus points (11) than your SFXn (1) and more chance for a wrong choice.
  • AF-C on the K10D sucks (historic fact...sorry) and is not generally recommended
  • K10D AF for moving objects sucks (also historic fact...sorry x2)
  • Adjustment to the AF system is possible in debug mode, but will be global in effect. AF and focus confirm will be shifted for all lenses. This should be done only if a global issue has been determined.
I used my K10D for seven years and was generally happy with its AF system except for anything involving action. For those types of subjects, I generally had to shut the AF off and fall back to time-honored manual focus techniques.


Steve


Last edited by stevebrot; 08-16-2014 at 10:27 AM.
08-16-2014, 04:38 PM   #5
Junior Member




Join Date: Mar 2014
Posts: 29
Original Poster
Imageman and the two Steves - thanks for your interest and input. I'll be going through all your points carefully. This situation makes me feel like the beginner I thought I'd left behind me.
I don't understand why a lens would focus well on a film plane and differently on a digital sensor unless the camera sets the lens at a different distance from each plane - simply a physical difference between camera bodies - but it seems that's what happens. I find it incredible that they'd be deliberately made so differently. Back to you when I've had a chance to go into things slowly and carefully.
Mike.
08-16-2014, 05:53 PM   #6
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,187
QuoteOriginally posted by Mike Gallagher Quote
I don't understand why a lens would focus well on a film plane and differently on a digital sensor
It probably doesn't since the lens is not doing the focusing, the body is. Much depends on the AF system as well as how it is being used. To isolate the cause of your soft images:
  • Try to forget that the lens ever worked properly with your film camera
  • Rule out camera motion and/or subject motion
  • Does the AF consistently work properly with other lenses? If no, the fault is likely with the camera or how it is configured.
  • Is the Tokina consistently sharp at all focal lengths for both near and far when manually focused (don't use focus confirm)? If not, there is an optical fault with the lens that will not be remedied by fiddling with the AF system.
  • Does changing the mode to AF-S with single center point AF take care of the issue? If so, the problem was simple misfocus. It happens.
  • As noted in my previous comment, do your testing with a flat target. This allows you to have control over the intended point of focus. Anything else increases the number of variables and the difficulty of finding the cause.
There is an outside chance that there is a subtle interaction between the optical and mechanical qualities of the lens and your K10D that might not have been present with your SFXn. That kind of bias is the whole reason behind the per lens calibration feature found on current model cameras. Your K10D lacks that feature and while the universal bias of the AF system may be adjusted, such adjustments should be done with care since they affect all AF lenses as well as focus confirm for manual focus glass.

Oh, one other thing. Try shooting in daylight, not artificial lighting. The spectral transmission of your Tokina may not work well with certain lighting on a modern AF system. The K10D tech is almost 20 years newer than that of your SFXn and a few things may have changed.


Steve

Last edited by stevebrot; 08-16-2014 at 06:04 PM.
08-18-2014, 07:16 PM   #7
Veteran Member
Imageman's Avatar

Join Date: Dec 2013
Photos: Albums
Posts: 461
Forget about lenses focussing differently on film cameras and digital cameras, its just plain wrong.


The plane of focus falls identically on whatever sensor is used whether that is a sheet of film or an electronic sensor.


In fact the basic theory is that a 50mm lens will form an image of a subject residing at infinity, 50mm behind the lens. the lens is racked forwards and backwards until a sharp image (the plane of focus) falls on the sensor, this is either done by the camera in AF systems or the photographer using manual focus.


The AF system is designed to bring the subject (whatever falls under the chosen AF point) into sharp focus. The camera manufacturer calibrates this AF system so that when the AF system thinks correct focus lock is achieved the sensor will see the image as sharp.


Different manufacturers use different distances between lens and sensor and always have, that's why you can put a Nikon lens on a canon camera and it will focus all the way to infinity, but you cant put a canon lens on a Nikon camera it wont focus at infinity because the lens is too far away from the sensor due to a larger mirror box on Nikon cameras than on Canon. (you of course use mount converters to swap lenses in this way), but the AF system doesn't care about lens to sensor distance, it is simply calibrated by the manufacturer so that it works.


Put simply, an AF system has detectors that can detect the difference between a sharp and an unsharp image, and theres one detector sitting under each AF point. You select the AF point to suit the subject, and the AF system racks the lens until the AF point recognises that the image under the chosen point is focussed, then it stops racking the lens.


The process is identical whether its a film camera or a digital camera, and if the calibration of the AF system is correct it all works perfectly. If however the calibration is slightly askew, then front focus or back focus issues appear as has been very competently explained by the 2 steves.
08-20-2014, 01:03 AM   #8
Junior Member




Join Date: Mar 2014
Posts: 29
Original Poster
Gentlemen - thank you so much for your willing and unstinting help.
It is possible that I've found the cause of my problem and if so an adjustment in the camera's menu re allowing Autofocus Lock was to blame but I have to do a decent series of shots to confirm that. I found a setting back to Factory Default and took a stab at that and some things seem to have come right.
I'll try to work out just what happened and give you a detailed report as soon as I can.
Again - thanks so much for your help. At the very least you've increased my understanding of what goes on.
Mike.

08-20-2014, 09:35 AM   #9
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,187
QuoteOriginally posted by Mike Gallagher Quote
Gentlemen - thank you so much for your willing and unstinting help.
It is our pleasure! I hope you have continued success.


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!
af, focus, focus problems k10d, k10d, k10d with tokina, pentax help, tokina
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Image 28/2.8, Kiron 28-210 PK/A, Tokina 75-150/3.8, Tokina 70-210 F4-5.6 PK/A, 80-200 MightyMike Sold Items 65 03-14-2013 07:19 PM
For Sale - Sold: Tokina AF 70-210 Zoom Lens dcshooter Sold Items 5 12-15-2012 02:34 PM
First shots with the Tokina 70-210 jezza323 Post Your Photos! 4 04-27-2009 02:58 PM
Tokina AF 70-210 f4.5 (constant) ecwoj Pentax SLR Lens Discussion 7 03-07-2009 04:22 AM



All times are GMT -7. The time now is 11:27 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