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05-29-2009, 03:24 PM   #1
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Trouble focusing with M lens

I recently purchased two Pentax M lenses on ebay to use on my K20D. From reading everyone's helpful posts, I understand how to use the green button and MF with the lens. My problem is that I can't get the subject in focus. I think I made a mistake when I first put the lens on my camera. The camera asked me to put in the focal length of the lens. I put in 50mm because that is the type of lens I bought. I'm wondering if this is my problem. Unfortunately I can't figure out how to enter a different focal length. Has anyone else had this problem?

05-29-2009, 03:29 PM   #2
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You entered the correct focal length. It is used by the camera to calculate how much SR to apply if you have SR turned on. It should not affect focus (unless you set it to a wildly different value than that of the lens).

You will likely find it hard to focus manually with the stock focusing screen - especially if you're not used to focusing manually with other cameras. A split-prism screen will help tremendously, as will an eyepiece magnifier. It can be done without these, but requires a good bit of practice.

P.S. The camera should ask you for the focal length every time you turn it on, if an M/K/M42 lens is attached.
05-29-2009, 03:47 PM   #3
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How do I select a split-prism screen on the K20D? is that in the custom setting menu?
05-29-2009, 03:47 PM   #4
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Make certain your diopter is set right - the viewfinder numbers must be sharp.

The stock focus screen is optimized for autofocus lenses, so a really bright lens like an f1.7 is trickier to focus. The screen will make it look like more is in focus than really is. You can compensate by putting your subject in the middle of the in-focus zone, not just looking in focus. That's where practice comes in. Focus (manual or auto) is easier in bright light and high contrast.

To reset the SR focal length setting quickly, just turn the camera off and on.

05-29-2009, 03:49 PM   #5
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QuoteOriginally posted by garfield160 Quote
How do I select a split-prism screen on the K20D? is that in the custom setting menu?
No, it's something you have to buy to replace the screen in the K20D.

Something like this:

Diagonal Split Image Focus Screen 4 Pentax k10D k20D DS - eBay (item 350143195534 end time Jun-18-09 05:26:43 PDT)
05-29-2009, 03:56 PM   #6
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QuoteOriginally posted by garfield160 Quote
How do I select a split-prism screen on the K20D? is that in the custom setting menu?
You have to purchase a split-prism screen separately. Here is one option:

Pentax K10D K20D Focusing Screen - Katz Eye Optics

It's not absolutely necessary and there are drawbacks. There are some very long threads about them in the accessories section. I would read them before deciding on replacing your screen. I really like mine, but everyone has a different mix of manual focus lenses, money available for the screen and focusing ability.
05-29-2009, 04:55 PM   #7
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QuoteOriginally posted by garfield160 Quote
.... My problem is that I can't get the subject in focus. ....:
When the green hexagon in the viewfinder lights up the subject is in focus.

Or set menu/AF _mode to AF.S Press the shutter button& hold it down as you slowly rotate focusing ring; the camera will take the photo when focus is reached (called "focus trapping".)

Iowa Dave

Last edited by newarts; 05-29-2009 at 05:24 PM.
05-29-2009, 05:00 PM   #8
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Note: I'm writing this based on my K10D. K20D may not be the same, but should be similar.

I twice tried to use two different split image focusing screens but finally gave up and am currently using an LL-60 screen. There are two main reasons why I gave up on split image focusing screens:

1. Incorrect exposure with manual lenses. In this regards, the split image screen is NOT worse than the stock screen (LI-80) but the LL-60 screen helps a lot. Another point (minor to me) is that the split image screen renders spot metering practically useless.

2. Black-out with lenses with small max. aperture (f/4.5 and smaller). One of my walkaround lenses is a Tamron 18-250 f/3.5-6.3. The black out at small aperture is very distracting. Also, at macro magnification of 1:2 - 1:1, the effective aperture of my f/2.8 macro lenses becomes somewhere between f/4 and f/5.6. Then the black out happens and manual focusing becomes even more difficult.

I now rely on my eyes and on the in-focus confirmation in the viewfinder.

With practice, I think you will find it doable.

About changing the focal length for shake reduction, you can turn the K20D off and on, or if you already have it on, use the last item on the [Rec. Mode] Menu. See the K20D manual pages 72 and 67.

05-29-2009, 05:14 PM   #9
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QuoteOriginally posted by newarts Quote
When the green hexagon in the viewfinder lights up the subject is in focus.
Well, *something* is in focus, not necessarily the desired object.
05-29-2009, 08:47 PM   #10
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QuoteQuote:
SOldbear: 1. Incorrect exposure with manual lenses. In this regards, the split image screen is NOT worse than the stock screen (LI-80) but the LL-60 screen helps a lot. Another point (minor to me) is that the split image screen renders spot metering practically useless.
I have a Chinese Split Prism and I only use Spot Metering--I have no problems. I just make the necessary adjustments. That said, I have heard & can see why it frustrates a lot of users.

QuoteQuote:
SOldbear: 2. Black-out with lenses with small max. aperture (f/4.5 and smaller). One of my walkaround lenses is a Tamron 18-250 f/3.5-6.3. The black out at small aperture is very distracting. Also, at macro magnification of 1:2 - 1:1, the effective aperture of my f/2.8 macro lenses becomes somewhere between f/4 and f/5.6. Then the black out happens and manual focusing becomes even more difficult.
I do not get a black out problem until 5.6 and many screens resist blackout until even smaller apertures--there are lots of reports of this throughout our forum.

I use my Tamron 90mm f2.8 with the Split and love it. I do not have any problems with this setup--can you describe what you mean in more detail? Actually, I couple the Tamron to a Tamron 2x BBar and still manually focus with precision. I am not sure what accounts for the problems you were getting. Here is an example of Spot Metering, with the Split Prism & Tammy 2x doubler--manually focused. Which focus screen were you using?

Last edited by Jewelltrail; 09-25-2009 at 09:10 AM.
06-22-2009, 05:16 PM   #11
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QuoteOriginally posted by SOldBear Quote
Note: I'm writing this based on my K10D. K20D may not be the same, but should be similar.

I twice tried to use two different split image focusing screens but finally gave up and am currently using an LL-60 screen. There are two main reasons why I gave up on split image focusing screens:

1. Incorrect exposure with manual lenses. In this regards, the split image screen is NOT worse than the stock screen (LI-80) but the LL-60 screen helps a lot. Another point (minor to me) is that the split image screen renders spot metering practically useless.

. . .
Actually the LF-80 is the stock K20d screen. This:



This is the Li-80:



I can't seem to find anyone that has used this screen in the K20d.
06-22-2009, 07:03 PM   #12
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Before you go off and buy a replacement screen...

If you are having trouble getting your image in focus and you are sure that the diopter is set properly for the view finder, the next most likely culprit is the lens itself. The image may well be in focus, but the image quality may be compromised due to contamination or damage to the lens.

Take the lens off the camera and examine it closely for internal fungus or hazing or other "stuff" inside the lens. This is best done with the lens off of the camera in subdued light using a small flashlight (torch) to illuminate the interior of the lens.

Steve

(There was a thread about a similar problem last week...)
06-22-2009, 07:04 PM   #13
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The Li screens are of limited use to most of us who are not into micrography. The LL screens have an engraved grid that I find very useful to keep horizons aligned and trees standing upright. The LF screens have just the indicators for focus area and metering.

I am awaiting the delivery of my second LL-60 screen, having dropped my original one in a lake. The -60 screens are from the *ist series, and give better metering for those of us who use lenses without the "A" position on the aperture ring. If you have "A" available on all your lenses you don't need to change the screen series from -80.

I do not use microprism or split prism screens because of the blackouts when I need the screen most - Using my M 400 lens with or without a tele converter. I use the matte screen to focus.
06-22-2009, 09:00 PM   #14
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QuoteOriginally posted by Canada_Rockies Quote
The Li screens are of limited use to most of us who are not into micrography. The LL screens have an engraved grid that I find very useful to keep horizons aligned and trees standing upright. The LF screens have just the indicators for focus area and metering.

I am awaiting the delivery of my second LL-60 screen, having dropped my original one in a lake. The -60 screens are from the *ist series, and give better metering for those of us who use lenses without the "A" position on the aperture ring. If you have "A" available on all your lenses you don't need to change the screen series from -80.

I do not use microprism or split prism screens because of the blackouts when I need the screen most - Using my M 400 lens with or without a tele converter. I use the matte screen to focus.

I was just notice on the Katzeye site that the current screens for the K20d are the new "Plus" versions that supposedly can go to f11 or beyond before blacking out. I'm wondering how many of the people that have used a Katzeye in their K20d had the "Plus" version. Apparently the same thing for the K200d.

Anyway, throw in the Jinfinance, the double split image, Katzeye, focuscreen.com, etc. and there are too many permutations and options.
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