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04-18-2011, 09:13 PM   #31
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You might have to shim the split prism screen. Shimming is 'finetuning' of the position of the screen and you need shims for that. Needed to do it on both my K10D and K100D.

04-18-2011, 10:21 PM   #32
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QuoteOriginally posted by justtakingpics Quote
I get the confirmation beep from my k-x but the images, for the most part, are blurry. Nothing picture is crisp so it's not like I focused on a part of a shirt but not the face (I was doing outdoor portraits).

Some images were ok, none what I would call super crisp - but good images. Most pictures I take are out of focus. I do not have this problem with the kit lens AF. Is it me moving or something?
FWIW, I collected some info and advice on manual focusing here. I use MF 99.9% of the time and the accessory I went for to make things easier is the O-ME53 magnifier loupe. Much easier to install than a focusing screen.

Keep in mind that the K-x has a less than optimal viewfinder. Unlike its higher end brethren, it uses a pentaprism (vs. pentamirror in K-5) that offers less magnification and clarity to begin with. I find it harder to focus with the K-x too. I'm actually amused because everyone kicked the K-7 around for having high iso issues, but in practice you can get better pictures with it in low light, because you can get the focus right more often with it and that beats extra noise any day.
04-18-2011, 11:31 PM   #33
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QuoteOriginally posted by justtakingpics Quote
If I put a split prism focusing screen on, will it affect af in any way?
No, the AF mechanism has nothing to do with the focusing screen or viewfinder, so you're OK.

As has been said, it probably will affect spot metering, but I would guess that this wouldn't be too much of an issue ("spot" metering is rather specialised, and the camera probably doesn't do it very well anyway).

I must say, I bought a (cheap) focusing screen over a year ago, but have never plucked up the courage to install it in my K-m! Also, I worry about having to mess about with shims.

However, don't let me put you off! As has been said, plenty of people have swapped screens and are getting the benefits of easier, more accurate and repeatable focus. And re-shimming may not be necessary anyway.

By the way, I recall the days of shooting with my MX (a film Pentax), and seem to remember that I used to focus just using the "ground glass" area of the screen - in other words, not making use of the split-prism. However, this is more a testament to the MX's superb viewfinder image, rather than any shortcomings of the split-prism.

If you do go in for a replacement screen, I would imagine the best type of focusing aid would be the diagonal split-prism.
04-19-2011, 12:29 AM - 1 Like   #34
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QuoteOriginally posted by justtakingpics Quote
Are they pretty easy to put on? You're just putting them on the mirror right?
Here's an instructive video:



04-19-2011, 02:07 AM   #35
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QuoteOriginally posted by JohnBee Quote
Or... if you prefer VF, incest in a split prism focusing screen
Heaven forbid !
04-19-2011, 04:08 AM   #36
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QuoteOriginally posted by Schraubstock Quote
Heaven forbid !
lol

That's almost as embarassing as the time I was talking with a live Pentax support personnel and wrote... every-time I took a sh!t... "instead" of shot.
Needless to say, the support person found the news rather disturbing

Oh and excellent video btw!
But there's a few things I'd change.

1. I would never work in a mirror box with any type of metal(whatsoever). To risky.
2. I think its better(easier) to work with the camera upside down. That way the shim and screen can't fall out.
3. It's best to wear surgical gloves or(at least), finger cots when handling or working with your screen. - this way if/when you come into contact with anything, it doesn't get contaminated with finger prints and/or oils from the hands etc.

Last edited by JohnBee; 04-19-2011 at 04:14 AM.
04-19-2011, 05:39 AM   #37
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QuoteOriginally posted by JohnBee Quote
That's almost as embarassing as...
I know what you meant, just couldn't resist a little dig, these little blunders are always so delicious.

Greetings
04-19-2011, 10:05 PM   #38
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QuoteOriginally posted by m42man Quote
No, the AF mechanism has nothing to do with the focusing screen or viewfinder, so you're OK.
Actually, the focusing screens that help with manual focus get dimmer at small apertures, so they may make AF systems fail earlier than normal with lenses that are have slow maximum apertures. I.e. AF may work up to f/8 with the factory screen, but may only work up to f/5.6 with a custom viewfinder. That is why stuff like OptiBrite exists. See this page from KatzEye.

If you only use fast lenses, it doesn't matter, but if you also have zooms that get to f/6.3 at the long end, a focusing screen may impact AF.

04-19-2011, 10:52 PM   #39
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QuoteOriginally posted by Laurentiu Cristofor Quote
Actually, the focusing screens that help with manual focus get dimmer at small apertures, so they may make AF systems fail earlier than normal with lenses that are have slow maximum apertures. I.e. AF may work up to f/8 with the factory screen, but may only work up to f/5.6 with a custom viewfinder. That is why stuff like OptiBrite exists. See this page from KatzEye.

If you only use fast lenses, it doesn't matter, but if you also have zooms that get to f/6.3 at the long end, a focusing screen may impact AF.
No, I'm afraid you've misunderstood the KatzEye article - it doesn't actually say anything about the focusing screen affecting AF, only MF.

You'll find a diagram showing an early version of Pentax AF here:

Pentax Auto Focus Systems

As you can see, light from the lens is directed downwards to the AF mechanism, which then uses techniques similar in principle to the split-prism in order to ascertain correct focus.

(Regarding the video "Changing the K10D focusing screen" - this isn't mine, it's just something I found on the Net a while back.)
04-20-2011, 07:20 AM   #40
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QuoteOriginally posted by RioRico Quote
Everything io said, especially final item (4) -- learn to focus manually. It takes practice, breath control, practice, movement control, practice, visual control, practice, patience, practice, some swearing, and lots more practice. With lenses with wide-enough bases, CIF (catch-in-focus) also helps a great deal.
TRIPLE YES!!!

QuoteOriginally posted by Laurentiu Cristofor Quote
FWIW, I collected some info and advice on manual focusing here. I use MF 99.9% of the time and the accessory I went for to make things easier is the O-ME53 magnifier loupe. Much easier to install than a focusing screen.

Keep in mind that the K-x has a less than optimal viewfinder. Unlike its higher end brethren, it uses a pentaprism (vs. pentamirror in K-5) that offers less magnification and clarity to begin with. I find it harder to focus with the K-x too. I'm actually amused because everyone kicked the K-7 around for having high iso issues, but in practice you can get better pictures with it in low light, because you can get the focus right more often with it and that beats extra noise any day.
I use this and not any other focusing screen and it seems to work for me. Further, I believe the on screen in focus indicator as well as the green box works well... if you practice, practice, practice...

You will get slightly different results going from infinity to focus v minimum to focus... there will always be a little play in the "in focus" indicator, maybe an 1/8 to a 1/4 inch turn where the focus indicator will still be lit up (and I can tell you, from experience, the correct focus is never in the middle)... this is where practice makes perfect. I would practice on a newspaper, on a specific word, and check your results, you might find you've got the camera pointed at a slightly different direction than you intended, etc...

FWIW - my K-m seems to be more accurate than my K10 in regards to the focus indicators. I've cleaned my focusing screen on the K10 and I agree with others here that turning the camera upside down makes it easier and safer to remove/replace screen if you want to go that route...

Good luck and just practice...
04-20-2011, 08:43 AM   #41
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QuoteOriginally posted by Laurentiu Cristofor Quote
Unlike its higher end brethren, it uses a pentaprism (vs. pentamirror in K-5) that offers less magnification and clarity to begin with.
Other way around. The K-x has a Pentamirror and the K-5 has a Pentaprism.

Pentamirror - Wikipedia, the free encyclopedia

Pentaprism - Wikipedia, the free encyclopedia
04-20-2011, 08:56 AM   #42
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Re: Aftermarket focusing screens & calibration:

I bought one of the cheap Chinese screens for around $15 from eBay for my K100D. Works great. Installation is a bit intimidating until you actually dive in & do it. Then it's not that big of a deal. Just be sure to wear latex gloves & don't touch or scratch the screen.

There's also a fair chance you'll need to calibrate your screen with the correct shim. I had to. You can get all 6 shims from Pentax for around $7 plus shipping. It's time-consuming, but worth it.

Good luck!
Bobbo :-)
04-20-2011, 10:26 PM   #43
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QuoteOriginally posted by m42man Quote
No, I'm afraid you've misunderstood the KatzEye article - it doesn't actually say anything about the focusing screen affecting AF, only MF.
You're right. Thanks for the correction. I mixed things up. I gotta stop posting when I'm tired.

QuoteOriginally posted by boriscleto Quote
Other way around. The K-x has a Pentamirror and the K-5 has a Pentaprism.
Right. That's what I meant to say, but it came out like it did.
04-23-2011, 09:21 AM   #44
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QuoteOriginally posted by Laurentiu Cristofor Quote
You're right. Thanks for the correction. I mixed things up. I gotta stop posting when I'm tired.



Right. That's what I meant to say, but it came out like it did.
Shimming sounds like rigging something to me. Is this something that is also easy to do? I was hoping for a snap in but shimming is worrying me.
04-23-2011, 09:25 AM   #45
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QuoteOriginally posted by m42man Quote
I know I'm slow but I just watched this. Thanks. Great video.
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