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Forum: Pentax SLR Lens Discussion 12-01-2013, 11:59 AM  
AF Fine Adjustment for Zoom Lenses
Posted By RockvilleBob
Replies: 6
Views: 3,423
I've been trying out the new FocusTune Ver 3 program that automates the calibration of the best AF Fine Adjustment for a lens/camera combination. Version 3 of the program provides repeatable results which leads me to have more confidence in the setting. I am in the process of doing the calibration for all my autofocus lenses with the K-3. The results for the DA*16-50 are somewhat surprising. The adjust value goes from + to - depending on the focal length.
Lens DA* 15-50
Focal Length
AF Adjustment
50 mm +5 to +6 35 mm -2 to -3 28 mm +3 to+4 21 mm -6 to -5 16 mm -3
The shape of the curve showing back focus to front focus through the range of AF settings looks about the same, However where the curve provides the best focus on the target chages from +AF setting to -AF setting as shown above.

I will be testing two other zooms, Sigma 70 to 200 and Sigma 150 to 500. Fo5 the 150 to 500 I really just use two setting 400 and 500 so it will be good to know the settings.

Since the settings are repeatable, they are probably close to correct.

So if I am doing a composed shot with f2.8 on a tripod that I plan to print I'll probably set a one time AF setting (I need to keep a card with the lens) Otherwise just set at zero and and increase DOF.

I'd appreciate others findings for AF Adjustment settings on Zoom lenses. I will also post results for the Sigma 70-200 and 150-500 if the results are significantly different in thier profiles.

For those not familiar with FocusTune 3.0 (it will be released for sale in about two weeks) check this out

Forum: Pentax News and Rumors 11-09-2013, 02:37 AM  
DA limited 20-40 f/2.8-4 mounted images
Posted By Pen-A
Replies: 107
Views: 33,790

20-32mm/f4.0 and f4.5 to 42mm :)
Forum: Troubleshooting and Beginner Help 11-08-2013, 11:49 PM  
Problem with focussing screen
Posted By vonBaloney
Replies: 11
Views: 1,157
Focusing screen has zero effect on AF. It does effect metering somewhat though.

AF adjustment is a whole other thing. The K10D doesn't have it (without entering "debug" mode), but all the newer models have AF adjustment you can set for individual lenses.
Forum: Troubleshooting and Beginner Help 11-08-2013, 10:45 PM  
Problem with focussing screen
Posted By vonBaloney
Replies: 11
Views: 1,157
Simply put, I don't think he's actually right about that. He needs to do controlled tests. Basically the concept is simple -- throw a ruler on a table in front of the camera so it is going away from you. Now from in front of the table put the camera on a tripod or fixed somehow just a bit above table height. Now focus on a point on the ruler -- because of the extreme angle it should only be possible to focus sharply on a very small area -- like a single hash mark on the ruler. Make sure everything is locked down, note what the mark is, take the shot (at the widest aperture), now compare the focus of the actual photo and see if your chosen hash mark is in-focus or if the real focus point is in front or behind. Then adjust shims on screen to move it forward or back by a tiny amount, replace screen, repeat until dead on.

Now, it is true some (older, likely) lenses will have a focus shift when they are stopped down from wide-open. That's not the focusing screen's fault. If that is the case, you just have to mentally compensate or stop down before you focus, and hopefully there will still be enough light showing. If you do these tests while focusing at the widest aperture (which is what you normally do) and also shooting at that same aperture, then focus shift won't be an issue.

Oh, and before you start, set the diopter on your eyepiece properly for your eyesight and leave it there forever -- adjusting it after shimming the screen can throw things off for you a bit. If two different diopter settings seem about right, just pick one and stick with it. And if while doing manual focusing tests you find your eye getting tired and it is getting a bit harder to focus, stop and take a break. Do it with fresh eyes.
Forum: Pentax Film SLR Discussion 11-04-2013, 08:12 AM  
Which Pentax film camera is equal to Nikon FM2
Posted By LesDMess
Replies: 56
Views: 16,937
Pentax didn't implement 1/4000 shutter speed until the AF body SFX/SF1 (1987) -> Pentax SFXn/SF1n - Pentax Autofocus Film SLRs - Pentax Camera Reviews and Specifications
Before then, 1/2000 was the top shutter speed and initially made available to the ME Super (1980) followed by the LX (1980), ME F (1981) and Super A/Super Program (1983). The Nikons with the 1/4000 shutter speed (FM2, FE2 & FA) became available in 1983.

Basically, the KX and MX are similar in functionality with the KX having MLU and the MX being smaller with changeable focusing screens. The ME Super and LX are the aperture priority capable bodies with the LX with much more sophisticated features - interchangeable viewfinders, TTL flash, weather seal, frame accurate forward, backward advance multiexposure, widest meter range and a hybrid shutter with 1/75 - 1/2000 available in manual if battery dies. All of these have the split image focusing screen while the MX and LX have additional user changeable types.

The FM2 - and practically all Nikon manual SLRs, have a much smaller viewfinder magnification of 0.83X compared to the KX at 0.88X, MX at 0.97X, ME Super 0.95X and LX depending on viewfinder from 0.55X to 1.35X with diopter adjustment.
Forum: Welcomes and Introductions 03-28-2013, 10:25 AM  
Greetings to all
Posted By galgulus
Replies: 97
Views: 9,498
"เรียน คุณบัญชา เลขบัตร ป.ช.ช. 5 ตัวแรก ของคุณ เลขอะไรเอ่ย และคุณเกิด จ.ว. อะไร " ผมว่าคุณแปลไม่ออก
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