16-50 problem ?

hi all,
I am not sure if there is something wrong with my lense, I both have the 16-50 and the 50-135, very happy with the second one no issue at all, the 16-50 is actually very stiff on the zoom ring, is that normal ? i noticed also that there is maybe some back focus issue, i would like to post a pic but im not sure how to do it. I do realize that is difficult to help without a proof but at least if u can tell me if the problem with the ring is normal.

thanks very much

claudio

I have not noticed any stiffness with my 16-50.

G

---

Keywords: Charming, polite, and generally agreeable.

Neither have I.

---

Hyram

Bodies: K20D (2), K10D, Super A, ME Super, Auto 110 SLR, X70, Optio P70
Pentax Glass: DA* 300, DA* 60-250, DA* 50-135, DA* 16-50, DA 70 Ltd, FA 31 Ltd, DA 35 Ltd, DA 18-55 (2), DA 12-24, DA 10-17, M 200, A 35-70, M 40, M 28, Converter-A 2X-S, 1.4X-S, AF 1.7, Pentax-110 50, Pentax-110 24
Other Glass: Sigma 105 macro, Sigma-A APO 75-300
Flash: Metz 58 AF-1 P, Pentax AF160FC ringflash, Pentax AF280T

Mine is rather stiff at one point and not smooth all the way through the range.

The SDM on that lens is now making a squeaking noise. Sounds like an old rusty gate swinging inside.

The 50-135 is built very well. In fact I've actually dropped it from about three feet six months ago and it is is working flawlessly with almost every day use.

The 16-50 on the other hand is, lets say, not the highest quality product I've bought.

To post an image join this free website

http://photobucket.com/

Then browse your images and upload the one you have selected.
When it appears as a thumbnail left click on the grey "IMG code". It should then say "copied" by the cursor. When you post here just paste on a new line and your image should appear.

---

K100D Super, 18-55, 50-200, Sigma 10-20, Sigma 70mm macro and lots of old lenses

My 16-50 is a little stiff at the wide end but smooth after about 28mm. I think this is due to the two barrel extension system. The first is stiffer, the second is smoother. As for backfocus, I£e found this is my K10 being miss calibrated. I fixed it using a hacked firmware and now what I see in focus in the viewfinder is in focus in the actual shot. Previously the viewfinder and sensor were so far off manual focus and autofocus would both be quite useless.

---

Regards,
Dan

https://www.flickr.com/photos/honourabletyr/

maybe I'm missing something but I don't see how a firmware hack could fix the viewfinder being off? The AF system fine, but the viewfinder screen is at a set physical distance from the focal point of the lens. If it's off surely you need to move the screen?

---

you don't have to be mad to post here



but it does help

I think what Tyr's saying is that he had the same problem as me, ie when something looked to be pin-sharp in the viewfinder it was out of focus on the sensor. I too used the firmware hack (in conjunction with the calibration chart) and find it's made a world of difference - what I see in the viewfinder is now what the sensor sees too.

The hack won't alter the viewfinder in any way, just bring the sensor into line with it.

---

Joining the Q

How does it do that?

---

~Pete

When you do the adjustment, the figure you alter is in tens of microns. I took this to be moving the sensor forwards or backwards by this tiny, but obviously significant, amount.

Right or wrong, my AF and MF has been much better since, especially with the wider aperture lenses I have (50 1.4, 300 2.8 ).

Dan

---

K-3, a macro lens and a DA*300mm...

Thanks for that Dan! I knew I was moving the sensor back-and-forth by incredibly small amounts but I couldn't figure out what the units were - now I know.

And yes, mine only required a movement of 30 microns but the difference in both MF and AF accuracy is night and day. These show the test charts taken with the FA43 @ f1.9 (both AF aimed at the black line; the second was taken at exactly 45 degrees in daylight - the first was just to confirm suspicions and was taken under tungsten the previous night minutes before I downloaded the firmware hack). It's safe to say I was having a bit of a back-focus problem there! Not any more though...

BEFORE ADJUST:



AFTER ADJUST:

---

Joining the Q

That's okay, although I said that, and can't remember where I knew it from. Does it say it on the adjustment screen? Anyway, when I said "tens of microns", what I meant was just "microns", as the figures are in tens.

Mine wasn't backfocusing as much as yours, but I think I ended up dialing in 60 or 70 as an adjustment. I do wonder if different lighting has an effect.

Dan

---

K-3, a macro lens and a DA*300mm...

Don't read too much into the first example, at really wide apertures then lighting does play a role and tungsten seems to exaggerate any problems. The "proper" tests I did before and during adjustment were done under natural light at exactly 45 degrees and the back focus - while still clearly evident - wasn't nearly so pronounced. Strangely enough though, it now seems to work just fine wide open under tungsten lighting too so I'm a very happy bunny!

---

Joining the Q

Hello.
I have just ordered the 16-50 2,8 lens. I didn't know about QC issues and FF/BF. I am really concerned about firmware fix because I've noticed that this problems occur widespreadely. So before i put my hands over my new lens I'm afraid I will have those issues too and I'm posting some questions for those who will feel about helping me with some informations.

Where can I find the firmware hack?
Do I need to go back to firmware 1.1?
Is it possible to revert to 1.3 after applying the modifications?
Does the modifications to the sensor alignment put out of focus the other -non DA*- lenses?

Thank you in advance!

First of all, download the focus test chart from www.focustestchart.com/chart.html and follow the instructions to find out if your camera actually has a FF/BF issue (not all do).

If it does have a problem then install the hacked version of firmware 1.10 over the top of your version 1.30 (http://www.vietzon.com/red/forums/viewtopic.php?f=7&t=33).

Now install the real 1.10 over the hacked version (still available from: http://www.pentax.ca/digital/digital_slr/k10d/firmware_110.php)

Switch on your camera while pressing "Play" and "OK".

Press "Fn->Fn->Info->Menu" within 5 seconds and change DEBUG MODE from <DIS> to <EN>.

Press OK.

Press Menu, then come along to "Set-up" and press ^up^ on the D-pad. You'll see "AF test" (select it) and you want to change the slider at the bottom of that page (positive correction for BF, negative for FF). Keep tweaking/shooting/tweaking until you get the right shot with the test chart.

When you've done exit Debug mode by switching off and on while pressing "Play" and "OK" and quickly pressing "Fn->Fn->Info->Menu" again. Change Debug Mode from <EN> to <DIS>.

You can now put version 1.30 back and keep the changes that you have made.

This is all entirely at your own risk and neither I nor anybody else will take responsibility for your actions! Make sure you use fully charged batteries or you'll ruin the camera and end up with a very expensive paper-weight.

Good luck!

---

Joining the Q