Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
07-16-2010, 11:55 PM   #1
New Member




Join Date: Jul 2010
Posts: 1
Occasional off focus using M42 to K adapter

Hi,

I recently took over some old lens from my dad and got a M42 to K adapter for my K10.
The lens is a Super-Takumar 50mm f1.4 by Asahi Pentax.

I am quite sure that I mounted the lens properly, but there are times when I have a great of difficulty focusing. The problem occurs in bright sunlight, even when I see that my subject is focused in my viewfinder, once I snap the shot, the focus is off. Way off. Its like I have focused on something else complete. But this doesn't occur all the time, when I am pointing my camera to say a table lamp's bulb or my computer screen, it works out fine, everything is PIN sharp, I can see the pixels on my screen.

There also seems to be a problem metering, my pictures will seem overly dark using M42 lenses.

I am not sure what is wrong. I really treasure these lenses, after all my dad got them when he was my age, I hope to be able to use them frequently

Thanks for your help!

07-17-2010, 01:16 AM   #2
Pentaxian
Steinback's Avatar

Join Date: Jan 2008
Location: GTA, ON, Canada
Photos: Gallery | Albums
Posts: 1,672
Both focus accuracy with fast lenses and metering accuracy on the K10 have been widely discussed here on the forum.

In brief, the stock focus screen doesn't display depth of field accurately below about f/3.5. This is one of the reasons many people who use fast lenses buy an aftermarket split prism screen which provides a focusing aid and a more accurate representation of depth of field.

Because the lens doesn't communicate with the body, metering accuracy changes depending on the aperture that you are using. Once you get used to how much the meter over or under exposes at each aperture, you can use exposure compensation or intentionally offset exposure based on the meter for whatever aperture you are using. I've been using both methods for years with my Tak collection.

I suggest looking through (and contributing to) this thread: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/31601-takumar-club.html

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/77151-foc...n-reviews.html

Sooner or later Lowell will probably post or link to his favourite K10d metering offset graph.
07-17-2010, 03:07 AM   #3
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
QuoteOriginally posted by calvin18 Quote

I am not sure what is wrong. I really treasure these lenses, after all my dad got them when he was my age, I hope to be able to use them frequently
I treasure mine and I only got them when I was my age minus three. What is wrong is that the stock focus screen may be great for auto-focus lenses but it is utter crap for manual focus. If you expect to use manual lenses extensively you will do well to replace it with an aftermarket split-prism screen. When I bought my K20D the very first thing I did when I got home was to sit down at the computer and fire off an order for a Katz-Eye screen. There are cheaper alternatives and you already have a link to a thread discussing the pros-n-cons of various models. More important than which screen you choose is that you do choose something and replace the screen.

There is no reason why you can't enjoy your M42 lenses to your heart's content. I use them on a daily basis as my regular gear and they are typically all I carry with me.

The various complaints about the metering of the K10D is why I never bought one.
07-17-2010, 04:01 AM   #4
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
I don't have a link to the chart Steinback mentioned at my fingertips but I have posted it so often it should not be hard to find

I also agree with mike

I have a chineese diagonal split screen in my K10. Not o ly does it make manual focus a snap but the split image screen did help on the metering as well.

This is also shown in the chart

07-17-2010, 04:11 AM   #5
Inactive Account




Join Date: Feb 2010
Location: New Delhi
Photos: Gallery | Albums
Posts: 74
QuoteOriginally posted by Mike Cash Quote
I treasure mine and I only got them when I was my age minus three. What is wrong is that the stock focus screen may be great for auto-focus lenses but it is utter crap for manual focus. If you expect to use manual lenses extensively you will do well to replace it with an aftermarket split-prism screen. When I bought my K20D the very first thing I did when I got home was to sit down at the computer and fire off an order for a Katz-Eye screen. There are cheaper alternatives and you already have a link to a thread discussing the pros-n-cons of various models. More important than which screen you choose is that you do choose something and replace the screen.

There is no reason why you can't enjoy your M42 lenses to your heart's content. I use them on a daily basis as my regular gear and they are typically all I carry with me.

The various complaints about the metering of the K10D is why I never bought one.
Second that.
I had to take 3 shots every time I used a manual lens till I changed to a split prism. Suggest the same for you, as long as you do not mind losing spot metering.
I do not miss it and have got around it by tabulating all the under/over exposure levels for all the lens I have (Auto as well as Manual).
I have an M42 300mm Takumar, which I am now able to use without focusing problems.
BTW: I presume you M42 adapter with infinity focus?
07-17-2010, 07:49 AM   #6
Pentaxian
Steinback's Avatar

Join Date: Jan 2008
Location: GTA, ON, Canada
Photos: Gallery | Albums
Posts: 1,672
I should have mentioned earlier that I went with a a Katzeye screen for my camera but that was mainly because I got a used one for a good price. The K10d and K20d (which use the same screen) have been around long enough that the screens show up in the forum marketplace fairly regularly.
07-17-2010, 04:50 PM   #7
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,167
I will join the chorus here in support of using an aftermarket screen for manual focus lenses. I got mine after months of mediocre results with much loved older lenses. Once I could actually focus, there was no looking back.

A few cautions:
  • The split image focus aid will affect spot metering if you use that mode
  • Aftermarket screens are not as bright as the stock screen. Things are pretty dim when using the 18-55 kit lens for instance and any other lens who's maximum aperture is narrower than f/3.5. This is true even with the Optibrite treatment on a Katzeye. That is the price that is paid for focus accuracy
  • The focus aids are a bit of a distraction and a bother when doing macro and close-up photography


Steve

P.S. My Katzeye on the K10D meters identical to the stock screen
07-18-2010, 10:29 AM   #8
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Split prisms can definitely help, but so can practice. I can't think of any actual lens or camera problem that would cause what you are seeing, although *constantly* missing focus could be a misaligned focus screen. The issue with the viewfinder showing too much DOF at very large apertures is real, but then, if you are in bright sunlight, you should be able to shoot at f/4 or higher (as in, larger f-number / smaller aperture) with no issues.

It might help if you could post an image so we can see what you are talking about. The DOF issue wouldn't have you off by huge amounts. What's also possible is that it's often hard to avoid noticing things in front of your subject and trying to make them in focus, eben thoguh you know you *should* be focusing on your subject.

07-18-2010, 12:15 PM   #9
Veteran Member
Pentaxor's Avatar

Join Date: May 2009
Location: Vancouver, B.C.
Photos: Gallery
Posts: 6,513
I use 2 methods here. 1st one is using a split prism focusing screen + a 1.36 magnifying eyepiece combo for manual focusing. 2nd is using Live View Mode magnification which I only use for fixed subjects which is fine for longer focusing and longer exposure or when you can afford to set your camera on a tripod in a certain situation. the LV mode is also used as a reference if your focus screen is aligned spot on or not. the only bad thing about LV is that it is slow/laggy and is not recommended for fast focusing. although great for intricate miniscule close focusing.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
adapter, dad, focus, k-mount, lens, lenses, m42, pentax lens, screen, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
M42 adapter for pentax mount with focus confirm? zoe Pentax SLR Lens Discussion 6 03-24-2013 09:35 AM
K20 Occasional Manual Focus Off Super A Pentax DSLR Discussion 3 04-21-2010 09:02 AM
M42 Adapter: Can this type focus infinity? jocko_nc Pentax SLR Lens Discussion 6 05-08-2009 05:58 AM
Takumar M42 adapter infinite focus wildherre Pentax SLR Lens Discussion 6 03-08-2007 05:34 PM



All times are GMT -7. The time now is 11:13 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top