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Forum: Pentax SLR Lens Discussion 01-17-2016, 11:28 AM  
DA 15mm Infinity focus question
Posted By Siegfried
Replies: 14
Views: 1,679
John,
this does not indicate any potential problem. As for the first part of the question, it is a tricky one (assuming you carefully examined your photographs and you confirmed the lens focused properly at infinity. If you didn't, then you'd better have this done since you may just need to AF-adjust this lens, see K3/5 user manual for AF adjustment guide):
- many DA15 lenses behave this way;
- but some - lucky ones - do not;
- this is due to Pentax low quality control (but Pentax isn't the only one, see below);
- you can have this lens serviced at a shop or on your own, you only need screwdriver set (JIS preferred over Philips) and a rubber tool to remove the front ring. The lens disassembly procedure has been covered here on pentaxforums several times;
- many lads and lassies consider this behavior to be okay and normal, but the truth is that it isn't (this isn't normal even for short-tele lenses, let alone ultra-wide angle prime one), it's all because of cost savings which is the main trend of nowadays;
- if you don't do manual focusing and if you don't use any software in post-production which utilizes EXIF focus distance data to correct the perspective distortions, then you can leave this as is.

Cheers,
Zig
Forum: Pentax SLR Lens Discussion 12-17-2015, 12:23 PM  
Manual Focus Hit and Miss
Posted By Siegfried
Replies: 11
Views: 1,027
Alex,
the AF module - which among other things toggles that in-focus beep- and dot-assistants on and off - works with ANY lens attached, even with old M ones. For an PKA-mount lens which is able to communicate with the camera and has a lens ID it is the 'Apply one' setting in the AF micro-adjustment menu to dial the focus. If a lens isn't able to communicate with the camera - either because it is of Pentax-K or Pentax-M type with dummy K-mount or because its KA-, KAFx-mount databus is kaputt - it is the 'Apply all' setting in the AF micro-adj menu which goes used by the AF module to toggle those focus assistants on and off.

To all,
unfortunately, all the 3rd party split-screen and matte focus screens for APS-C Pentax cameras which are on the market have more or less wrong thickness thus it is mandatory to carry out the focus screen position adjustment. Some focus screen sellers offer adjustment shims, but if your screen came w/o those shims, feel free to make your own ones from aluminum foil found somewhere in the kitchen or taken from a candy. This adjustment is a pain in the ass, but it is a must.

Zig,
who has been shooting with several focus screens + O-ME 53 v/f magnifier and MF primes for 5+ years.
Forum: Pentax SLR Lens Discussion 11-12-2015, 10:36 AM  
DIY 21 Lim Service
Posted By Siegfried
Replies: 6
Views: 2,336
Hi, fellas.
There're several similar threads and posts about what's inside DA 21/3.2, but they are a bit unclear here and there and contain some errors. So I think it is worth to come up with mine. The background: I've finally come to a conclusion that I'm the 35mm-normal photographer (as you all know there're photographers who consider 50mm effective focal length to be the normal one and there're photographers, whose normal is around 35mm) and since Sigma isn't going to bring the 24/1.4 in the K-mount to the market, I've got no other choice, but to buy the DA 21 Limited. An order placed and in a week and a half later used - but as new! - lens is picked up.

I already own a copy of DA 15 Limited (bought brand new) and I do know what a Pentax Limited is about: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/145797-da15...-infinity.html
I had to open it and grease it and to optically adjust it before it started to feel, look and perform like something worth the Limited badge. And since the DA 21 is well known for coming apart - SUDDENLY! - there was no question if I should service it or not, but rather if I should have it done today or yesterday. So, if yours is going past infinity or can't reach the infinity focus or wobbles like a junk in the pond or you just got a brand new copy and are afraid whether it is going to break in half or not - read on!

N.B.: from my experience of reading people dissecting lenses, many of them are mechanically impaired so I decided to explain almost every step in detail. If you know the stuff well and don't need the basics, then you'll learn all you need from the pictures.

1. Here're the essential tools required:
Attachment 288226
Clockwise:
- a container to clean the screws;
- a thread-lock compound;
- a thread-lock remover (I prefer the acetone, but it stinks and you can easily damage the lens coatings, be careful);
- a tube of proper grease (main feature: must not vaporize giving you haze on the lens);
- precision screwdriver-set;
- a cotton-bud;
- a toothstick;
- tweezers;
- a clean A4 sheet of paper, A3 preferred.

2. Do not do anything on the rear-end. DA Limiteds are designed to be opened from the front. For a start you've got to remove the center decorative ring (or beauty ring as some say). See the next two photos on where to apply your 1.5mm flathead screwdriver and what to expect:
Attachment 288221
Attachment 288222

3. Using a proper-sized screwdriver (Number 0 if you speak metric or JPS #something if you're from the XIX century) undo those three screws and remove the front plate assy. Beware, whenever you use too big or too small screwdriver, you will damage the screw head. See the 11- and 3-o'clock screws on the photo above (I started with a Number 00 screwdriver but changed it to the proper one right when I felt that it gonna eat those screwheads).

4. Ok, here's the main assy:
Attachment 288223
The four center screws hold the optical unit while the three screws around hold the focus ring to the focus base-plate. Those three are the screws which all the oh-my-da21lim-just-fell-apart people are for.

Note lots of the thread-lock compound on the screwheads and around: THIS IS BAD, DO NOT DO THIS. Thread-lock should be applied to the screw's thread, not poured onto the screwhead! Get yourself some good automotive repair manual (better from '80s, the golden era) - I strongly recommend manuals from Robert Bentley Publishers - and learn how to deal the a threadlock.

5. If you lens assy is wobbling and feels like crap, read on. Otherwise, skip to #6.
You need to remove the four center screws. Rotate the focus ring into the infinite focus position. Using the cotton-bud apply the thread-lock remover onto the screwheads. Rub the cotton-bud on each screwhead until it's clean and your screwdriver firmly seats in it. Undo the screws. Remove the lens assy - but be careful no to lose the tilt-adjustment shims:
Attachment 288224

Make a note on what opening each shim was applied to.

Put the screws into the can and pour the thread-remover so it covers the screws. Get the can closed (what a smell, ya?) and keep rubbing the cotton-bud wetted with the threadlock remover on the screw seats to remove the threadlock remains if there're any.

Check each and every helical screw and bushing. If a screw can be tightened up, remove it, have the screw's thread cleaned and de-greased, apply the threadlock to the screw's thread and re-seat the screw all the way in. If the lens assembly is still wobbling, then you've got a bad copy and the only way to have it tightened is either to replace the whole assy or to apply a small amount of grease to the roller races/tracks while rotating it clock- and anticlockwise. Be careful not to spoil the grease on the lens. Re-seat the lens assy back onto the focus ring plate (close the aperture diaphragm so aperture lever goes into the slot of the interim lever on the lens rear-end). Mind those tilt-adj shims! Use the toothstick to center the shims against each opening (or on each hole as uneducated people say).

6. If you have a proper infinity focus on your DA 21/3.2 copy and if you trust in the Pentax way of applying the thread-lock, skip this section. Otherwise, remove those three outer screws using the technique from #5 (cotton-but wetted with threadlock remover to be rubbed on the screws and the plate... well, see above). No, you don't need to remove those two screws at 7-o'clock! No, you better do not do that! Clean the screws in the threadlock remover can as per #5 above. Clean the plate from the threadlock remains. If you inf focus setting is spot-on, apply the thread-lock compound on the screw threads and screw the fasteners in firmly. YES, FIRMLY. I came across some posts saying that those three screws should not be screwed in firmly or the focus ring does not rotate - this is false. It is the base-plate which handles the focus and the focus ring must be firmly secured to it.
If your inf focus setting is incorrect, you've got to rotate the focus base-plate to have it adjusted. Yes, it is the one underneath the focus ring which the focus ring is screwed on with those three screws. You don't need to remove the focus ring, just use tweezers or T5 screwdriver thru the focus ring openings to twist the focus base-plate clock- or anticlockwise. In a case you DID remove the focus ring or in a case of curiosity what it looks underneath, here's the fragile thing which your curiosity can damage:
Attachment 288225

7. Assembly is the reverse of disassembly as they say.

8. Re-check the AF performance and complete the AF micro-adjustment if necessary.

Good luck with your 21 Limited copy!

Zig
Forum: Pentax K-5 04-25-2012, 12:24 PM  
Focus Indicator Accuracy With Old Manual Lens
Posted By Siegfried
Replies: 24
Views: 5,575
Gentlemen,
I noticed that AF assistant accuracy was way off when using old (K-, M-) lenses. I really mean it, it's way off. I tried AF adjustments on the legacy menu and then I moved to the service mode and found out, that I could either live with AF lenses or MF ones, but neither both:
- thru the service mode I can set AF adjustments that way (+150 um), that my 15Lim and Tokina's AF270 and ATX280PRO are within the range of legacy AF adjustments (e.g. 0 for the Lim and -3 for Tokinas). But old MF lenses (ancient M42 Industar 50/3.5 with no coatings at all, M42 Helios 44 multicoated, K-mount Helious 77) are too much off the focus when that focus indicator beeps on
- thru the service mode I can adjust AF to -120 so that all my MF are quite spot-on, but then even set to +10 on the legacy menu I can't get even close to any precise focus with AF lenses

Even if I try to put it into extremes and adjust AF thru the service mode so that some lens is having +10, and other -10 and 'all' -10 - it doesn't work, it's just out of the range available on the legacy AF menu and needed for all those lenses.

I gave a call to local Pentax service center and was told that it was the way it's supposed to be. AF system requires some data (oh... what?!) from a lens on order to work and since MF lenses do not provide that data, then AF is no way precise with them. AF assistant aka focus indicator will be way off with all those old lenses of K-, M- and even A- series. They could not answer on why pentax still offers M42-K adapter as well as adapters for 645 and 6x7 lenses and do not offer any split-screen focusing screens. LV focusing works well, but there're many scenarios when LV is useless (e.g. for action photography or in bright light).

Here in Mordor things are slightly different and reps are not quite client-focused. So I decided to doulbecheck it and contacted Pentax USA thru the live chat on their website. Paul started doing his best, but after he noticed my IP address he said I had to turn to Pentax of Mordor (which I had already done, see above) since it was my geographic location. And he refused to provide me with any email addresses for 2nd line technical support.

So I'm asking if anybody here could do me a favor and spend half an hour of his life on the live chat with Pentax USA on their website asking for details on the AF design and whether it is really not meant to work with M- and K- lenses missing those electronic chips.

TIA,
Zig
Forum: Pentax SLR Lens Discussion 07-19-2011, 09:40 PM  
Helios 77M-4 MC 50mm F1.8 Have you used this lens?
Posted By Siegfried
Replies: 11
Views: 16,202
Metalwizards,
I've got this lens and have used it a lot. It's about the same biotar as all those helioses having that twisted bokeh wide open, pretty good general contrast and microcontrast (for MC variants, but all H77's came MC'd since they were made in late 80' to mid-late 90's). I've hit the limit for disk space here for my account, so you can refer to this link for photos:

the link

Most of the shots were made with H77M-4MC at f=2.8, only _IGP1293 was shot wide open and some (one or two) landscapes were done at f=8. Check 'aperture' field available under (i) 'info ' -> 'photo data' web-site page controls to confirm whether a shot was made with this lens or Tokina AT-X AF280PRO: if there's a certain aperture reported, then it's Tokina. Otherwise it's H77M4-MC at 2.8 (or 1.8 or 8, see above).

Bottom line: rare, pretty good baby of Helious family, recommended w/o any reservations, fair market price: up to $250USD for a decent copy. N.b.: focus ring goes the other way then one on Pentax, Tokina and Nikon glass: infinity is on the right and MFD is on the left (just like Sigma, Canon, Zeiss; Pentax, Tokina and Nikon have infinity in the left and MFD on the right). Sometimes it's a bit frustrating, but not that much.

Zig

P.S.
When saying smth about FMV I mean it's fair for something to have such price sticker. But probably you'll fail trying to sell it at this price tag since it's public opinion that goes 'I used to see this X at $5-15, you must be nuts asking $150'. I purchased my NOS copy for $150 a couple years ago and I'm pretty happy with it: both price and copy itself.
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