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01-16-2011, 08:32 AM   #1
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Manual focus questions

So, I have a K100D, which has served me well over the years. It is having some problems though, so I am considering replacing it. Basically, it crashes (shuts itself off), often losing the photo I am taking. It also performs very poorly in the cold now (to be expected, but it has gotten worse).

Also, I think flange distance is slightly off as all of my lenses can focus past infinity. At first I thought this was just a problem with older, manual focus lenses. The biggest offender was always my 50mm/1.4-m. I also have a 28mm/2.8-a which displays the problem. Until recently I thought it was just these lenses, which I bought in bargain condition from keh. I assumed they had been banged up a bit causing some alignment issues. The other day, on a whim, I tested the kit lens, and low and behold, it too focused past infinity when I switched to manual focus.

My guess is that the system is either designed this way, or the sensor in my camera is slightly off. Either way, I am probably going to replace the camera soon due to the crashing issue (very annoying).

My question is, has anybody else experienced this problem? With newer bodies? My guess would be that if it is a problem and not just a design issue that I was unaware of, it would be more prevalent on the lower end bodies like the k-x and k-r.

I have a second question as well. How much better is the viewfinder on the k-5 than the viewfinder on the k-r for manual focusing? I would have to drive at least 2 hours to get my hands on either camera, so I was hoping a knowledgeable individual could help me out. Even with a split prism it is hard to focus on the k100d, while I have no problems on my Nikon F3 (side note, the F3 has never failed in the freezing cold ), my Rolleiflex, or my rangefinders. Is the k-5 on par with the legendary F3? I enjoy using older camera equipment (especially the price), but I have been very disappointed with the manual focus experience on the k100d. So, is the k-5 noticeably better in that regard?

I appreciate any advise.

01-16-2011, 09:58 AM   #2
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I have an *istD and have never experienced the problems you list but the could be caused by poor batteries or poor memory card as well as the camera itself

As for MF focusing any of the dual wheel bodies will be better as a penta prison is brighter than a penta mirror

Regardless you will be best served with a split image focusing screen installed for MF lenses
01-16-2011, 10:16 AM   #3
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I've never had any of the problems you describe with the K10/20/7/5. With the K10 and K20 I had a Katzeye with a split screen but have forgone that on the K7 and K5. I seem to be able to do pretty well with manual focus on those cameras.

Pentax K28mm f2.0 - a set on Flickr

01-16-2011, 10:41 AM   #4
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Have you checked the battery contacts for dirt or corrosion. Try cleaning the contacts on the camera and the batteries. Have you tried new (known good) batteries in your K100? Try lithium cells. Have you updated the firmware to the latest version?
Many lenses will focus past infinity, designed that way, not a defect.

01-17-2011, 08:33 AM   #5
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Thank you all for the replies.

Yeah, the contacts are clean and I've tried many different sets of fresh batteries. I've also tried different memory cards since the problem seems to happen most often when writing an image to the card (the worst time it could happen in my opinion). I'm on the latest firmware as well. I have taken to shooting only in jpegs because they write faster than raw files and I seem to have fewer lost images that way. It is very annoying to take a picture and have the camera crash before it can finish writing the file.

Is there a way to tell if a lens is designed to focus past infinity? I've heard that some will have a click stop at infinity, but can, with a little effort, go past. With my lenses, I set it on the infinity symbol, and that results with focus beyond infinity. I have to set the lens to before the infinity mark to get distant objects in focus, which is what makes me think that it is problem with the camera. That is, the lenses do not turn past the infinity mark, it is just that the infinity mark does not correspond to distant objects being in focus. They do, however, appear much more in focus in the viewfinder than on the screen when the lens is set to infinity. I hope that makes sense.

Regarding the focus issue, maybe I'll just have to take a trip down to NYC to see how I like the K-5.
01-17-2011, 11:14 AM   #6
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I've been told that some AF lenses are designed to go past infinity a little bit so that a fine adjustment can be made by the camera at that end, rather than slamming against the infinity stops. I've never bothered to test the validity of that statement however. A Manual focus lens should not be able to be 'forced' past. Some thing is loose and will continue to loosen if you continue to repeat that exercise. The best way to tell if it's performing properly is to put it on a camera and use it.

01-17-2011, 11:22 AM   #7
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some lenses focus past infinity because they do not otherwise hold infinity at all the different temperatures.

differential thermal expansion between brass, plastic and aluminum canbe a real pain
01-17-2011, 12:20 PM   #8
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Indeed, Lowell. The first such Pentax lens was the first * lens they developed in the 1980s - the 300*. Focussing past infinity was on the feature list of this lens.

Jack

01-17-2011, 08:14 PM   #9
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So, basically, when it comes to infinity, the distance markings on lenses are useless? Why even have an infinity mark if it doesn't correspond to infinity. In my informal testing, on my camera, that mark never corresponds to infinity. When I shoot with the lens on that mark, everything is completely out of focus. The weird thing is that in the viewfinder, the scene does not appear to be out of focus. A little soft sometimes, but not completely blurry as it is in the final image.

I guess I'll just go with autofocus lenses in the future, because I really don't like the way focusing has been working with manual lenses.
01-18-2011, 03:18 AM   #10
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Tim

The marks are far from useless

I use them with manual focus lenses to set the approximate focus before I begin shooting

I do this because many older lenses have very long focusing throw and it is faster to preset focus to an approximate distance first

Also for hyper focal setting it is very useful (landscape photography and candid street photography where you don't even look through the viewfinder). But for many. Modern shooters they get very little use
01-18-2011, 02:06 PM   #11
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Hey Tim, all is not lost I hope and I'll try my best to bring your K100D back on track :-)

I have one such camera myself and use it exclusively with manual focus lenses. I am using the AF-lenses in manual focus mode too.

About the infinity, it's all been said before. Manual lenses go past infinity because of production tolerances. AF-lenses go past infinity so that the AF is able to overshoot (part of the concept of AF). If you are a meticulous photog you have to check the real, full open aperture, infinity setting on each and every lens with your given cam. On longer lenses you'd better check it right before shooting too because of temperature tolerances. We all do this :-)

About your camera acting up, I'd double check all contacts as been said before. Also, could you please check for any loose screws on the camera bayonet ? Somewhere else on the body ?

If all this has been done, please try to provoke the acting up by doing the following: With a given lens setup, try some buffer shooting (so you will have a long writing period, seen by the orange blinking light on the back).
Then, try moving any movable part of the camera while writing. This can be wiggling the lens on the cam, moving or distorting parts and especially the card door. I just tested the open/close function of my carddoor and the cam will almost immediately stop working when the card door is opened.

I haven't yet figured out where the contact is that actually tells the camera that the door is open, but that is my suspect #1 at the moment. Might be enough if just some dirt particle would enter the hinge of the door and block that contact. Might work if you just try vacuuming the whole card compartment (with an as small as possible nozzle in an as short as possible time).

How many shots do you have on the cam ? Did you read out the camera by the USB-cable or by taking the card out ?

Best of luck with a great cam imo.
georg
PS: About the cold problems, it could be moisture too. If the cam is very cold when coming indoors or the car, better leave it packed in a cold closed bag to warm up within a couple of hours so no condensation of water within will happen

Last edited by georgweb; 01-18-2011 at 02:25 PM.
02-27-2011, 08:28 AM   #12
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Oops, I forgot about this thread. I think georgweb is right about the memory card door. I can get the camera to crash fairly reliably by pressing on it. I probably do this when I hit the play button as well, which is usually when it happens. I guess I'll just have to be more careful. I rechecked everything else and there is no corrosion in the battery compartment. I couldn't find any loose screws either. At least there is something I can try to avoid now.

Regarding infinity. I guess I'll just try to get to NYC to try out a k-5 or k-7 and see if the screens are any better. My main problem is not that the lens focuses past infinity, but that a scene will look in focus in the viewfinder, but not on my computer screen. It makes it very hard to get decent shots at infinity. This is what made me think that something was out of alignment.

Thanks again. I'm gonna see if I can figure out why the camera thinks the memory card door is open when I press on it.
02-27-2011, 12:06 PM   #13
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It's not necessarily the sensor that is off. Can as well be the matte in the viewfinder.

I haven't heard of it with the standard matte that is installed during the production of the camera, but when I replaced the standard mattes of my K100D and K10D with Katzeye split prism ones, both needed shimming (adjustment).
02-27-2011, 02:37 PM   #14
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Agreed sterretje, the stock matte seems spot on, while my Chinese split prism one doesn't. Not sure how to adjust it though... using tape or so? Or is there some other, more elegant way? (Using a *istDS.)

I doubt though that any DSLR can compete with a fine SLR like the F3. My FM2 was way superior to any DSLR I have ever hold in hands. There, MF is as easy as pressing the shutter. My *istDs is pretty hard to MF, my eyes just aren't good enough (I'm using the AF sensor to assist me). And AFAIK no crop sensor DSLR beats it... as good as the *istDS, yes, better, no. IIRC the K100D was very decent too. But if you have problems with that, don't even consider the K-r or K-x.
02-27-2011, 03:47 PM   #15
hml
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I have the K20d and have had some success with manual focus. I'm thinking of getting a Katzeye to assist with the focusing. There are some other split focusing screens out there, does anyone have experience with one of those?
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