Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-21-2020, 02:11 PM   #1
New Member




Join Date: Oct 2020
Posts: 4
Pentax 6x7 Issues with Focusing / 75mm Lens

Hello all,

I'm new to the forum and also new to shooting with a Pentax and MF in general, so please bear with me--I have a lot of questions and I'll try not to overload here. I recently started shooting with a 6x7 equipped with an SMC Pentax 67 75mm/F4.5, and I'm having a few issues with focusing, as well as some stylistic issues now that I've gotten a few rolls back.

I believe the focusing screen in my camera is the microprism type, which from what I've read makes for a dimmer and more difficult focusing situation. The viewfinder is super dim, and I find it nearly impossible to tell through that tiny circle if I'm correctly focused or not. Is this just the norm? I'm really not sure if this is a result of the focusing screen, the lens, or a combo of both. Is there any recommended screen to replace this one with?

The focus altogether seems to be quite off. Aside from the fact that thus far I've only scanned my negatives with an Epson v600, which i know isn't ideal for sharpness and could be a big factor here, there is some strange blurring that occurs in the corners of my images (attaching some examples), almost like it's a tilt-shift lens. I truly have no more knowledge of this camera than what I've been able to find on forums like this, so I'm a bit overwhelmed wondering which part of my set-up is the faulty part, or if nothing's wrong and I just don't like the photos the camera produces.

I know this is kind of a rambling post, I'm happy to get into specifics if anyone wants to help--thank you in advance!

These examples were shot with Portra 400 and 160:

Attached Images
           
10-21-2020, 02:39 PM   #2
Site Supporter
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 6,906
Welcome to the forum!

A couple things to check.

1) Is the lens DOF lever on AUTO or MAN. If it's MAN then you will get a dim viewfinder.

2) Is the cameras finder mounted properly and does the focus screen/finder look OK and not damaged?

Phil.
10-21-2020, 04:41 PM   #3
Pentaxian
Silent Street's Avatar

Join Date: Nov 2011
Location: Alice Springs/NT AUS
Photos: Albums
Posts: 1,032
It's not a rambling post. Shamelessly, mine are though, and that's where you win!

The images shown are very underexposed, in addition to being quite fuzzy. Scanning can be almost as befuddling to unravel as faults or mis-steps with the P67 itself. There is evidence of unstable holding. Avoid handholding the Pentax 67 when you are just coming to grips with it, sorry for the pun. Invest in and use a tripod to gain the best in terms of sharpness at low shutter speeds.

If you cannot achieve correct focus easily, it is likely the dioptric correction lens attached to the eyepiece is of the wrong strength. These tiny lenses are not readily available on the used market now, and where and when they are, only the nearest correction factor is available e.g. if you need +2.5 you will only be able to find +2 correction. This is what I use on my 67 and it works fine.

Second point. The native focusing screen of the 6x7 / 67 (1969 and 1989 respectively) is grainy and quite difficult to focus in low light, very much so with any lens of f4 or slower, and I would consider a lens of f4.5 to be really pushing the ability to focus easily and correctly, notwithstanding the foregoing issue. Other focusing screens are available, but not necessarily brighter. To get around this requires, as the easier way, investing in a faster lens. Pentax does have an alternative 75mm, albeit with a skyhigh price tag at the moment: the 75mm f2.8AL (AL is for aspheric element) which will provide an exceptionally clear and bright viewfinder image, even with a polariser attached (which is routine for my work). I would not recommend using a polariser on any lens slower than f4 unless you have the patience of a Hindu cow.

Another area to investigate is calibration of the focusing screen. On a workbench, this calibration is done at three places around the central area of the viewfinder: central microprism, outer ring and near-outer matte area. It is usually done with the 105mm f2.4 lens using a focusing chart. If the meter coupling chain has at some stage been broken and the lens mount has been removed, after repair the lens mount must also be calibrated for correct focus, in the range of mere millimetres, any deviation of which will make focusing very challenging and unable to be compensated by stopping down to a deeper aperture.

With regard to the first query about dioptric correction lens, an optometrist may be able to fashion one for you matched to your vision. The sticking point is the lens has a fixed ring around it used to support it in the knurled ring that in turn screws onto the viewfinder. Sometimes even people with 20/20 vision encounter problems with the standard viewfinder lens: this can be a tell-tale indication of a problem with the alignment of the focusing screen, the lens mount or both.

So, there are a few things for you to check out now, starting with the viewinder eyepiece and after that, moving on to examining the focusing screen plane, and especially any evidence of tampering with the screws that hold it down. Anything more is generally best left to a service centre.

* Also see this thread regarding the correct process for removing and replacing the TTL metering prism and lens to prevent breakage to the meter coupling chain.

Last edited by Silent Street; 10-21-2020 at 06:43 PM.
10-21-2020, 06:16 PM   #4
Moderator
Site Supporter
Loyal Site Supporter
MarkJerling's Avatar

Join Date: May 2012
Location: Wairarapa, New Zealand
Photos: Gallery | Albums
Posts: 14,609
Thread moved to Medium Format part of forum.

10-22-2020, 07:30 AM   #5
New Member




Join Date: Oct 2020
Posts: 4
Original Poster
QuoteOriginally posted by gofour3 Quote
Welcome to the forum!

A couple things to check.

1) Is the lens DOF lever on AUTO or MAN. If it's MAN then you will get a dim viewfinder.

2) Is the cameras finder mounted properly and does the focus screen/finder look OK and not damaged?

Phil.
Thanks Phil!

1) Actually the lever has been on manual the whole time I've been shooting with it so far--I tried to switch it before to see what it did, but it never wanted to click into place. That is, until just now when I tried it again upon reading your response, ha. Thank you for that.

2) I believe everything to be mounted properly, and nothing seems damaged, just perhaps a tad dusty.

---------- Post added 10-22-20 at 07:42 AM ----------

QuoteOriginally posted by Silent Street Quote
It's not a rambling post. Shamelessly, mine are though, and that's where you win!

The images shown are very underexposed, in addition to being quite fuzzy. Scanning can be almost as befuddling to unravel as faults or mis-steps with the P67 itself. There is evidence of unstable holding. Avoid handholding the Pentax 67 when you are just coming to grips with it, sorry for the pun. Invest in and use a tripod to gain the best in terms of sharpness at low shutter speeds.

If you cannot achieve correct focus easily, it is likely the dioptric correction lens attached to the eyepiece is of the wrong strength. These tiny lenses are not readily available on the used market now, and where and when they are, only the nearest correction factor is available e.g. if you need +2.5 you will only be able to find +2 correction. This is what I use on my 67 and it works fine.

Second point. The native focusing screen of the 6x7 / 67 (1969 and 1989 respectively) is grainy and quite difficult to focus in low light, very much so with any lens of f4 or slower, and I would consider a lens of f4.5 to be really pushing the ability to focus easily and correctly, notwithstanding the foregoing issue. Other focusing screens are available, but not necessarily brighter. To get around this requires, as the easier way, investing in a faster lens. Pentax does have an alternative 75mm, albeit with a skyhigh price tag at the moment: the 75mm f2.8AL (AL is for aspheric element) which will provide an exceptionally clear and bright viewfinder image, even with a polariser attached (which is routine for my work). I would not recommend using a polariser on any lens slower than f4 unless you have the patience of a Hindu cow.

Another area to investigate is calibration of the focusing screen. On a workbench, this calibration is done at three places around the central area of the viewfinder: central microprism, outer ring and near-outer matte area. It is usually done with the 105mm f2.4 lens using a focusing chart. If the meter coupling chain has at some stage been broken and the lens mount has been removed, after repair the lens mount must also be calibrated for correct focus, in the range of mere millimetres, any deviation of which will make focusing very challenging and unable to be compensated by stopping down to a deeper aperture.

With regard to the first query about dioptric correction lens, an optometrist may be able to fashion one for you matched to your vision. The sticking point is the lens has a fixed ring around it used to support it in the knurled ring that in turn screws onto the viewfinder. Sometimes even people with 20/20 vision encounter problems with the standard viewfinder lens: this can be a tell-tale indication of a problem with the alignment of the focusing screen, the lens mount or both.

So, there are a few things for you to check out now, starting with the viewinder eyepiece and after that, moving on to examining the focusing screen plane, and especially any evidence of tampering with the screws that hold it down. Anything more is generally best left to a service centre.

* Also see this thread regarding the correct process for removing and replacing the TTL metering prism and lens to prevent breakage to the meter coupling chain.
Thank you for such a detailed response--I really appreciate you for that!

Believe me when I say I've gone completely down the scanning rabbit hole recently, quite overwhelming. And yeah I would agree they are underexposed but honestly that is just kind of my style . That said, I'm definitely not a fan of fuzzy. I'll be testing out the negatives on an Imacon soon to see how much of the problem lies in the Epson scanner. And yes, certainly would chalk up some of the issues to me handholding the camera--the shutter always surprises me with how much it moves the camera. Not sure why it didn't occur to me to use a tripod yet...over-excitement i guess!

Thank you for the lens recommendations! Had no idea where to start so I'll look into those.

As far as the diopter lens goes, I'm not really sure. I removed it to take a look, and when I look through it it just seems like a piece of glass. Does this mean it's the standard? I think I'll just fork over the money to take the camera to a specialist--luckily there seems to be a lot of those in NYC, just hoping I find the right one.
10-22-2020, 03:19 PM   #6
Pentaxian
Silent Street's Avatar

Join Date: Nov 2011
Location: Alice Springs/NT AUS
Photos: Albums
Posts: 1,032
QuoteOriginally posted by LoganJ Quote
As far as the diopter lens goes, I'm not really sure. I removed it to take a look, and when I look through it it just seems like a piece of glass. Does this mean it's the standard? I think I'll just fork over the money to take the camera to a specialist--luckily there seems to be a lot of those in NYC, just hoping I find the right one.
I'll be brief with this post, as it's a long weekend and camping is on the cards.

The "piece of glass" you saw unscrews from the knurled ring that holds the caboodle to the viewfinder. Take it to an optometrist who will be able to put it on a thingy a bit like a microscope in appearance, which measures the strength of glass correction. He could even be quizzed about the prospect of having a custom dioptric lens made for you, if you actually wear glasses (?).


I'm sure the Big Apple has more facilities for a Pentax 67 go undergo an examination under the skin, moreso than we have here in Australia, which is a big worry (people actually have sent their P67s to the US for repair, at enormous expense of freight, something like AU$340 insured, one way ).
10-22-2020, 04:44 PM   #7
Site Supporter
Site Supporter
StephenMerola's Avatar

Join Date: Feb 2009
Location: Wisconsin
Photos: Albums
Posts: 423
So now with the lens set to Auto is the viewfinder brighter? It should be. Also, moving the aperture ring should now have no affect because the lens will only stop down once the shutter is fired.
10-23-2020, 03:28 PM   #8
New Member




Join Date: Oct 2020
Posts: 4
Original Poster
QuoteOriginally posted by Silent Street Quote
I'll be brief with this post, as it's a long weekend and camping is on the cards.

The "piece of glass" you saw unscrews from the knurled ring that holds the caboodle to the viewfinder. Take it to an optometrist who will be able to put it on a thingy a bit like a microscope in appearance, which measures the strength of glass correction. He could even be quizzed about the prospect of having a custom dioptric lens made for you, if you actually wear glasses (?).


I'm sure the Big Apple has more facilities for a Pentax 67 go undergo an examination under the skin, moreso than we have here in Australia, which is a big worry (people actually have sent their P67s to the US for repair, at enormous expense of freight, something like AU$340 insured, one way ).
Ha, I think I will do that--luckily I have an optometrist in the family! I wear contacts, but I'd think that wouldn't have any effect since there's no glass lens involved? Was wondering about that actually.

10-23-2020, 03:38 PM   #9
New Member




Join Date: Oct 2020
Posts: 4
Original Poster
QuoteOriginally posted by StephenMerola Quote
So now with the lens set to Auto is the viewfinder brighter? It should be. Also, moving the aperture ring should now have no affect because the lens will only stop down once the shutter is fired.
I actually just realized that it was in fact set to Auto the whole time....

I guess for some reason i thought that the lever hovering over "manual", that meant it was set to manual And now I suppose I'm back to being unhappy with the focusing screen! I'm not even sure what the difference between the auto/manual settings for this type of lens is?
10-24-2020, 02:15 AM   #10
Site Supporter
Site Supporter
johnha's Avatar

Join Date: Apr 2012
Location: Lancashire, UK
Photos: Albums
Posts: 1,083
In Auto the aperture remains fully open for focusing and metering only stopping down to the value selected on the aperture ring during the exposure.

In Manual, the aperture is always stopped down to that selected on the aperture ring.

At anything other than the widest aperture (i.e. f/4.5) using the lens in MAN will result in a darker focussing screen (depending on the aperture set). When switching to AUTO, you may need to lift the tip of the AUTO/MAN switch gently to lock it in place.
10-24-2020, 09:36 AM   #11
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 12,416
I found the 75mm lens to be the most difficult one that I had to get accurate focus from.
10-25-2020, 05:37 PM   #12
Pentaxian
Silent Street's Avatar

Join Date: Nov 2011
Location: Alice Springs/NT AUS
Photos: Albums
Posts: 1,032
QuoteOriginally posted by LoganJ Quote
Ha, I think I will do that--luckily I have an optometrist in the family! I wear contacts, but I'd think that wouldn't have any effect since there's no glass lens involved? Was wondering about that actually.
Your contacts will have a correction factor and it could well be found there is a mismatch between them and the lens fitted to the viewfinder of the 67.
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!
645d, 645z, 6x7, calibration, camera, correction, examples, f4, focus, issues, lens, look, medium format, pentax, pentax 6x7 issues, pentax help, photography, polariser, screen, troubleshooting, viewfinder
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Pentax 6x7 300mm F4.0 and Pentax 6x7 200mm F4.0 MightyMike Photographic Equipment for Sale 55 6 Days Ago 08:03 AM
For Sale - Sold: Pentax 6x7 300mm F4.0, 6x7 200mm F4.0, 645-A 200mm F4.0 MightyMike Sold Items 58 12-27-2019 12:30 PM
6x7 75mm f4.5 lens cap sandy_ada Pentax Medium Format 3 12-30-2017 07:05 PM
For Sale - Sold: Pentax SMC 6x7 75mm f4.5 Shift lens Rorschach Sold Items 3 10-04-2013 06:29 AM
Manual Lens focusing issues (focusing screen) Akarak Troubleshooting and Beginner Help 15 01-25-2013 06:56 PM



All times are GMT -7. The time now is 10:15 AM. | See also: NikonForums.com, CanonForums.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