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Forum: Pentax Full Frame 04-06-2015, 03:12 PM  
The Full Frame: What will make you buy it?
Posted By tibi
Replies: 131
Views: 18,342
Coming back to the main question of this thread, "what would make you buy the FF", here's what I would like the Pentax FF to have/be like. I'm a hobbyist photographer who has a thing for shooting film, so my remarks are influenced by my experience of using mostly the Pentax LX. As for digital, I own a K20D, so I might not be fully up-to-date with all the newest features in Pentax DSLRs.

1. Compatibility with all the old manual-focus K-mount lenses :
A de-crippled lens mount would be ideal, however I suppose Ricoh won't want to de-cripple the mount, in order to encourage people to buy new lenses. Nevertheless, stop-down metering at the push of a button is still good enough. I don't think we have reason to worry about compatibility in the case of Pentax. Lack of compatibility would be a show-stopper, as I would definitely switch to another system.
2. Big, bright, comfortable viewfinder
I think think we can also take this for granted in the coming camera.
3. Interchangeable focusing screens,
so I can install a split-screen and microprism focusing screen, to use with the old lenses. I have such a screen on my K20D and I like it more than the electronic focus confirmation. I don't see a reason why Pentax would discard interchangeable screens, so I don't worry much about it.
4. High dynamic range
I shoot mostly on film because I appreciate the extremely high dynamic range of negative film (the other major reason is that I can use the full field of my wide-angle manual lenses). It's nice to be able to have HDR with a single exposure and not have to do exposure bracketing.
In my case, I would be willing to accept a lower resolution in exchange for a higher dynamic range.
5. Features for making very long exposures / astrophotography:
- low-noise
- long-exposure noise reduction (dark frame subtraction) that can be deactivated (the K20D can't do this and it's extremely annoying, I suppose it's no longer a problem for newer bodies)
- locking the mirror up by up to 10-20s before the exposure starts, to leave more time for vibrations to stop (the K20D only allows 2 seconds)
- a cheap bulb remote (or press shutter button to start exposure, press again to end)
6. Good handling
I consider the handling on the K20D as excellent. Even better on the newer bodies since they're more compact. Keep up the good work, Pentax!
7. As compact and lightweight as possible without compromising durability
My old LX accompanies me more often on my hiking trips than my K20D. If you've ever used the Pentax-M 20mm f/4 on a film body, you'll know how small a package that makes (with excellent IQ!). It's a joy to use!
Of course, you can't make a digital full-frame as small as a film camera (you need space for all the electronics, for the LCD etc.), but if the new FF could be made comparable in size to the APS-C models, that would be great. In my case, I would be willing to do away with the swivel LCD to make the camera more compact; I suppose other users would disagree on this point.
8. Weather-sealing
I think we can pretty much take this for granted from Pentax.
9. Good video capabilities
as good as the competition at the time of launch.

"Excellent IQ, excellent autofocus ..." and many other useful features have already been expressed by other members, so I won't restate them. I just wanted to express my point of view as mainly a nature photographer who doesn't want to ruin his back hauling a big, clunky camera up into the mountains but still wants high IQ. I could do this with a mirrorless camera or one of the newer Pentax APS-C bodies, but I really like my old lenses and I want to be able to use them at their full potential. That's the main reason why I use the LX more than the K20D.

And a small thought on de-crippling the K-mount:
I would be willing to bet that at some point, someone at Pentax thought that "the old lenses are killing our sales of new lenses". These old lenses should not be viewed as a threat, but as an asset. Pentax's DSLR market share is low compared to canikon. And the way to increase market share is not by trying to sell lenses directly, but by increasing the number of bodies out there. A strong incentive to buy the Pentax FF would be its compatibility with all the Pentax lenses ever made, at their originally intended FOV and preferably with open-aperture metering. In time, these buyers will want to benefit from the higher IQ afforded by newer optical designs, they will want to replace a set of primes with a zoom of achieving the same quality thanks to the newer design, or they will feel the need for AF and will therefore invest in new lenses. The old lenses would then be sold to others, perhaps new people upgrading to FF who do not yet have the budget to buy new FF lenses alongside their new FF body.

If someone from Pentax/Ricoh is reading this, I would also like to point them to the Nikon Df as an example of a beautifully crafted camera, made for "pure photography". I love its looks and its controls and the fact that it fully supports all Nikon lenses. If I would have been a Nikon user, I would have bought that camera in a heartbeat! My only griefs with it would be that it lacks a video mode (I think that's a bit too much "pure" in "pure photography") and that it remains relatively big.
At this point, I don't think that a DSLR in Nikon Df's style would be the best thing since it would scare away some people; I would rather keep with the modern layout for now. However, it would be nice to see a retro-styled, compact, digital FF "Pentax LX" in a few years from now.
Forum: Maintenance and Repair Articles 11-05-2014, 06:48 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
This sounds like some sort of "software hack", to fool the camera into thinking the infinity position is elsewhere. I'm not sure how much this fix would help in the case of Pentax AF lenses. If you use a screwdriver to turn the focusing screw inside the lens mount, you'll hit the same hard stops at the ends. If infinity can be reached somewhere during the travel, the AF system of the camera can find it on its own, no need to do any strange meddling. And if the lens consistently front/back-focuses, you should compensate from the Pentax DSLR settings menu (I don't remember where, I've never used the feature, but I know it's present).
Forum: Maintenance and Repair Articles 10-03-2012, 12:52 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
Great to see that this article is useful!

Most polarizers, except really-really good ones, are quite far from being perfectly flat. That's because they're harder to make than other filters, they have more layers and they are made of stuff that's more difficult to work with. Small errors in the flatness of each layer accumulate. When used on lenses with short focal lengths (say, 50mm or less), you don't really notice the effect. On longer lenses, the magnification of the lens amplifies any errors in the filter.

I, too, noticed this problem. I had a cheap, no-particular-brand (ok, Vivitar IS a brand) circular polarizer. On the 18-55mm, I never noticed any problems. On the 50-200mm, no matter how I turned the focus ring, I couldn't get a sharp picture. Took the filter off, everything was back to normal again.

I once stumbled upon a test of various polarizing filters. Among other things, they test the homogeneity of the filter. Here's the link:
Polarizing filters test - Introduction - Lenstip.com
Even some filters from very respectable brands had problems with homogeneity.

So, an addendum to the infinity focus fixing article: take the filters off when doing this!
Forum: Maintenance and Repair Articles 09-04-2012, 08:14 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
Thanks for your comment, Baldrick. I would like to clear some things up. "Modern lenses" yes, often can focus past the infinity mark, and it is absolutely no problem. You have autofocus anyway, and the autofocus doesn't care about the distance markings on your lens, it just finds the correct focus. The same thing happens if you focus manually, but with a split-screen or a microprism (like on old film bodies, or if you've changed the focusing screen in your camera): you just turn the focusing ring until your image is no longer split.

HOWEVER, my lens was unable to turn until the real infinity, it was off by a lot! And you simply couldn't turn the focusing ring any further, because it has a hard stop at infinity. This is why all the pictures of distant objects looked blurry, because the lens could only be focused about as far as 100-150m, and on long lenses, 150m can't be approximated with infinity, the depth-of-field is too small.

So my advice is:
If your zoom lens focuses past the infinity mark, don't bother fixing it, because zooms are often varifocal (focus distance depends on zoom), as baldrick said.
If your fixed-focal lens focuses past the infinity mark, again, no big problem, because you CAN reach infinity somewhere in the focus ring travel. The only time when it's useful for the focus travel to stop exactly at infinity is low-light photography and especially astrophotography, where there isn't enough light to judge focus, and you just need to focus at infinity. Generally, it's actually better to allow the lens to focus a little bit past the infinity mark, to allow for thermal variations (especially true for very long lenses, 200mm+).

BUT if your fixed-focal or zoom lens CAN'T reach true infinity, meaning it can only focus closer than infinity before the focus travel reaches its hard stop, then you have a problem. This problem usually occurs after someone has taken apart the lens for servicing, but he/she hasn't reassembled it exactly the same way. Get your lens reassembled properly.
A similar problem arises when using M42-K adapters that are too thick: the lens can't be brought close enough to the sensor to allow focusing at infinity. Look for an adapter that's thinner.

If you have a new lens that can't reach true infinity, take it back for a warranty exchange/repair. The problem is easy to spot, you can't get in-focus shots of distant objects no matter how you focus, but the shots of stuff that's closer look nice and sharp.
Forum: Maintenance and Repair Articles 01-22-2012, 06:38 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
Indeed, thermal expansion isn't really noticeable on a 200mm lens (unless maybe if used in extreme environments). I think that for this lens, the wrong infinity focus was simply due to improper previous disassembly and reassembly. Whoever took the lens apart before me probably forgot to mark the 'true' infinity focus position.

If you want to adjust your lenses, search the web for additional info, because not all Pentax lenses are disassembled exactly the same way.
Forum: Maintenance and Repair Articles 09-22-2011, 07:17 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
You're right, Michael. It's highly recommended to use latex gloves. I would also like to add that I also have a film camera now, and I re-checked the focus adjustment on that. With the microprism focusing screen, you can easily set the correct focus. I saw that I've overcompensated a little bit, maybe I'll open the lens again some day and tune it to perfection. :)
Forum: Maintenance and Repair Articles 09-18-2011, 06:46 AM  
How to fix infinity focus on K 200mm f2.5
Posted By tibi
Replies: 16
Views: 18,171
Hello to everyone!

I've managed to adjust the infinity focus on my SMC PENTAX 1:2.5 200mm, and I thought I'd share the experience with you, maybe someone else might find it useful, too. :)
Here's a picture of the lens:
Attachment 103897


Before I begin, a legal disclaimer: the technique described here worked for me, it doesn't necessarily mean it will work for you, too. I DO NOT ASSUME RESPONSIBILITY IF YOU DO SOMETHING BAD TO YOUR LENS AS A RESULT OF THE TECHNIQUE THAT I HAVE PRESENTED HERE. IF YOU DECIDE TO DISASSEMBLE YOUR LENS, YOU DO THAT AT YOUR OWN RISK. IF YOU ARE NOT PREPARED TO ACCEPT THESE RISKS, THEN DON'T DISASSEMBLE YOUR LENS. INSTEAD, CONSULT A PROFESSIONAL SO THAT HE MAY DO THE REPAIRS.

How I found out that I had infinity focus issues: because all the stuff that was very far away appeared blurry in the pictures, when the focus ring position was set to infinity. But stuff that was closer (at about 200-300m) appeared sharp, even wide-open at f/2.5, when the focus was set on the infinity mark. Images at infinity got somewhat sharper when I stopped down the lens, but this was only because the DOF increased when stopping down. To achieve true focus at infinity, I would have needed to turn the focus barrel just a bit more, two or three degrees, past the infinity mark, which of course was not possible.

This lens focuses by moving all the optical elements together towards the front (to achieve close focus), or towards the rear (for infinity). So I needed to make the optical elements move towards the rear just a little bit more, to hit infinity right-on.

What you'll need to open the lens:
- a good PH 00 screwdriver (with a long enough blade, so that it will be able to reach into narrow spots), avoid the interchangeable tips screwdriver sets, because their body is too thick and you can't reach inside the lens
- an air pump (like the rocket blower), to remove those few dust particles that inevitably settle on the inside lenses
- a clean workplace
- an object that's very far away, at least 2km, on which you can check infinity focus. A far-away mountain peak, or the Moon, make excellent targets. Avoid looking above hot asphalt, or over rooftops in the summer heat, because this creates a lot of turbulence in the air, and makes it more difficult to check sharpness.

Also, it is advisable that you put a clean cloth under the lens while you work, so that those little screws won't go far if they fall on the table.

Now let's begin the disassembly:

Extend the lens hood and you will see three little screws keeping the hood and the filter ring attached.Unscrew them and remove the lens hood. Don't mix up these screws with those from the lens hood, because they're of a different length.
Attachment 103898

Attachment 103899

Now unscrew the entire front group as a whole (grab onto the bottom-most ring, otherwise you'll unscrew the front part of the group). Remove the front group from the lens.
Attachment 103900

Attachment 103901

Now, for those of you who need to also do maintenance on the aperture blades, this is also how you access the front part of the blades. I don't know how to access the rear part of the blades, as this wasn't my objective, and I only took apart strictly what I needed to.
Attachment 103907

Now you'll see three more screws, unscrew these also and remove that metal thing that they keep attached. Be careful not to drop these screws into the lens (keeping the lens horizontal when working with these screws might be a good idea).
Attachment 103908

Attachment 103909

Now, if you look inside the lens, you'll see that the focus barrel (the rubberized thing on the outside of the lens, that you turn to focus) attaches to the focus helicoid (I believe that's how it's called?) by means of three screws. When you turn the focus barrel, it then turns the exterior part of the helicoid (please correct me if the terms that I'm using aren't entirely correct), which then moves the central part of the lens (the one containing the optical elements) forward or backwards. The screws are marked with red (you can also see the reflection of these screws on the inside of the focusing barrel).
Attachment 103911

What you need to do now is to loosen these screws so that the rubberized focusing barrel will be able to turn freely, so that it doesn't also move the inner part of the helicoid (which would then cause the optical elements to move forward or backwards). DO NOT UNSCREW THESE SCREWS COMPLETELY, JUST LOOSEN THEM! If you've taken these screws out completely, good luck putting them back in!

Now that you've loosened those screws, you have to turn the focusing barrel a bit, in the appropriate direction, so that you compensate for the previous focusing misalignment. My lens only managed to focus to about 200-300m, so BEFORE I loosened these screws, I set the focusing barrel on the infinity mark, then loosened the screws, then turned the focusing barrel to where I thought the 200-300m distance should correspond (see the picture, where, after loosening the screws, I align the focus mark to be just a little bit before infinity). Then I tightened back the three screws.
Attachment 103912

If your lens, unlike mine, focuses PAST infinity (you get the clearest pictures of objects at very high distance when you set the focus to be actually before the infinity mark), then do the following: BEFORE disassembling the lens, make a note of the position on the distance scale where you achieve TRUE infinity focus. Then follow all the steps described above to disassemble the lens. Before loosening the three screws described above, set the focus barrel on what you found out to be true infinity focus. Now loosen the three screws (be careful not to rotate the focus ring while you do this), then turn the focus barrel so that it reaches the infinity mark. Now re-tighten the screws.

Note: it's good to tighten these screws well, so that the focusing barrel won't slip later on, after you've assembled back the lens. However, don't tighten them like a brute, either, in case you'll need to disassemble the lens again for maintenance, in the future.

Now you can assemble back the lens. Test to see if infinity focus is good. Note that on a lens of this focal length, you have to check infinity on a target that's very far away (I recommend at least 2km. The Moon makes quite a nice target)! Also, when checking focus, make sure your diopter adjustment for the viewfinder is properly calibrated (or use magnified live-view, or take several photos to find the exact focus adjustment for the greatest sharpness at infinity). If it needs more adjusting, follow the same procedure again.

Congratulations, you've finished adjusting your lens! Now you can enjoy sharp pictures at infinity, sharp enough even wide-open! Now your only limitations in sharpness are camera shake and atmospheric turbulence.
Forum: Pentax DSLR Discussion 09-09-2009, 11:47 PM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
I think Peter Zack is right, it looks like a writing error on the memory card.
Forum: Pentax DSLR Discussion 09-05-2009, 12:57 PM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
Well, a week or so after I sent it in for repairs, they gave me a new camera body because they couldn't fix the old one. I hope the new body will last longer (much longer).

Thanks to everyone for their support!
Forum: Pentax DSLR Discussion 08-04-2009, 01:50 PM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
I've sent the camera in for repairs. Fortunately, I won't be needing it for business in the next few weeks, only for leisure.
As for the live view, I rarely use it, but indeed, the problem does seem to appear after taking a few shots and heating the sensor a bit.
Forum: Pentax DSLR Discussion 08-04-2009, 01:42 PM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
Yes, but the problem persists.
Forum: Pentax DSLR Discussion 08-03-2009, 03:04 AM  
K7 busted sensor strikes production body
Posted By tibi
Replies: 543
Views: 98,609
I've had a somewhat related problem with the K20D. But instead of a very faint line, I have a very thick band in the image. Take a look here to see some samples: https://www.pentaxforums.com/forums/pentax-dslr-discussion/68205-k20d-sensor-malfunction.html
Forum: Pentax DSLR Discussion 08-03-2009, 02:53 AM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
I've seen other people on this site having problems with their sensor, although there were only faint, thin lines.
Forum: Pentax DSLR Discussion 07-29-2009, 08:00 AM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
Yes, in fact, I only shoot RAW. The images above were extracted from RAW files. I've also tried changing the memory card, but the bands didn't go away.
Forum: Pentax DSLR Discussion 07-29-2009, 05:36 AM  
K20D sensor malfunction
Posted By tibi
Replies: 17
Views: 4,140
My K20D just started to misbehave yesterday. :(
In many shots, a thick green band appears near the left border of the image (it's actually composed of many thinner bands, close together). I've attached some sample images.

I've noticed a slight tendency for the band(s) to appear only after I've taken a few shots since turning the camera on, but the behavior is quite random. Some shots are perfectly ok, others are very bad. The band pattern differs from one picture to another, but it's always near the left border of the image.

One of the pictures is a long exposure (several minutes) with the night sky. In this image, the band is purple, not green. If you look closely, you'll also see a dark band to the right of the frame.

It looks like a sensor malfunction and I'm afraid the camera will have to make a visit to the repair shop. Has anyone else had similar problems? If so, how long did your camera stay in for repairs? I really need the camera back before August 11th but I fear it'll take a lot longer to repair. :( (I'm considering keeping the camera a bit longer and simply cropping out the bad areas as a temporary solution)
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