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Forum: Pentax Medium Format
05-22-2021, 08:36 PM
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Thanks to all. Yes, the lens is a later SMCP 90/2.8, not the LS version. I'm going to wait for the second and third rolls, which also contained some shots at 1/500 and 1/1000, to come back to me from the lab before settling in on it, but if no improvement is seen (I suppose there could be an atmospheric reason for the darkness on the left although I somehow doubt it) then it's off for a CLA. Would probably be a good idea regardless.
As far as I can tell from other threads, there are two P67 mail order service options: one has the initials LZ and the other is just a single individual with the initials EH. LZ lists a fairly benign price for a basic CLA service and I certainly don't have very severe issue right now with the 67 at least, so I wonder if they'd be the go-to for this. On the other hand, it's such a light touch of underexposure that I wonder if the expert EH who has the shutter testing machine featured prominently on their webpage would be a better choice (if they would even take it on).
Skilled P67 service seems like it will only get harder to find as time goes on.
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Forum: Pentax Medium Format
05-22-2021, 05:51 PM
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First time poster, long time reader. The Pentax Medium Format info here has been a great resource over the years.
There are some threads (like this one: Pentax 67, right side of the pictures are underexposed when shooting horizontally. - PentaxForums.com) in the forum history about users experiencing side-biased underexposure with 67's. Whatever its cause, it's always a darkening of one side of the frame.
My problem is that I've had a couple of 67's that seem to do this. Actually, the first was an older "6x7". Here's what it started to do after a while:
This photo was shot at 1/1000 in broad daylight. This slight underexposure on the left side started to appear at about the same intensity on all the photos taken with that camera at that shutter speed. Multiple subsequent rolls shot with a battery gave no improvement.
I eventually snagged another body, this one a "67". Besides just being newer, I've heard that they had somewhat upgraded mechanical and electric components. It certainly gave me lots of good use with completely uniform exposures even at the two fastest shutter settings. The problem is, it sat for about 9 months without use during this past year, and my first roll shot since then turns in this kind of thing for the two exposures made at 1/1000:
Just posting one here but the other shows about the same thing. Looking at the water in the bottom left and right corners gives you the best idea of the difference.
It's so subtle! But I guess I'm just attuned to look for it now. What are your thoughts on this? Is this sort of thing most likely caused by the shutter curtain slit narrowing slightly as it moves across the film gate? I know it's hard to say from just a single scan, but could it be something else?
Just to be clear, the first photo was taken with the older 6x7, and the second with the newer 67. Both were taken with the same 90/2.8 lens, and both were shot on Portra 400.
Do you think a technician would be able to fine tune the shutter to fix it? Is this something that happens with age on most 67's? I've searched and never been able to find anyone else posting about such a moderate exposure difference. It's usually a lot more severe, even compared to the darkening on the first photo/first camera, which I find to be stronger. But I figure it's not that uncommon, just not extreme enough to be of concern. I would like to keep using this camera on bright days with wide apertures and not have to add ND filters to bring my shutter speed down to 1/250, though.
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Forum: Pentax Medium Format
07-10-2020, 07:14 PM
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This photo was taken about a week after the incident, so unfortunately for me it’s probably not condensation, although I’ll try a desiccant packet in a ziploc cause it sure wouldn’t hurt.
I’ve... wondered about the idea of letting it get hot again, taking off the rear plate and ... going at it with a powerful vacuum. If the haze got moved onto the glass through vaporization, maybe it can be reduced somewhat in the same way. But I feel like I’d have to accept that the lens is trash first before attempting such a harebrained corse of action.
In seriousness, maybe I’ll ask Eric at Pentaxes about his cleaning it first before going to the big guys at Precision. Although as much as his name comes up around here and elsewhere I think he must be a very busy person.
And yes, this stings most because this 45 was as close to perfect as any manual focus super-wide lens I’ve ever owned. It’s fantastically even in its rendition from edge to edge; something I’ve found *so many* Nikon, Minolta, and even Zeiss wide primes to lack, in that they’ll have a ‘soft side‘ and a ‘sharp side’.
Come to think of it, all the P67 lenses I’ve had enjoyed solid centering and thus very even center-to-edge sharpness rolloff on all sides. But that in no way means that I’d trust the next P67 45 I buy to be well-centered. Hence my attachment to the one I’ve got.
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Forum: Pentax Medium Format
07-10-2020, 06:15 PM
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Thanks. Used these folks before?
It’s funny, there are two other places called ‘Precision Camera’ that I know of, and at least one of them (Precision Camera here in TX) doesn’t do lens disassembly jobs.
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Forum: Pentax Medium Format
07-10-2020, 12:53 PM
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Hello, I’m a longtime reader of Pentax Forums and gear reviews and this is the first issue I’ve had that wasn’t solved by searching through old threads:
It could’ve been avoided so easily, but the camera bag was left for about four hours in the back seat of the car in the middle of the Texas summer. By the time it was retrieved, all the contents were pretty warm to the touch. Looks like the P67 lenses (90/2.8 & 200/4 SMCP, 75/4.5 Tak, 45/4 SMCP6x7) all picked up a little bit of internal haze to some degree, I’m assuming from evaporated lubricants.
The 45/4 already had some haze behind the rear element. Now that haze is thicker and there are additional accumulations deeper down in the elements around the aperture. Here’s a picture showing the haze behind the front element : https://i.imgur.com/ZJiVZpV.jpg
The 45 got it the worst. I’m hoping that it’s not significant for the others, but I wonder if I’m going to need to either get the 45 cleaned or replace it. Too bad it’s the most complex lens design of the four, making it the hardest to clean. I think it even has a floating element.
Does anyone know of a mail-order service that does cleaning of old lenses like these? I suppose I need to get a quote and decide if it’s going to cost more to get the service than it is to buy a replacement. Good cosmetic condition 45’s seem to be going for north of $300 these days, and in my experience cosmetic condition doesn’t always track to lens optical quality (factory defects, centering problems, etc are alway still possible).
The 200/4 was mint perfect before being left in the heat. Now it has two streaks of haze behind the front element. The 90/2.8 also now has some behind the front element as well, and deeper in, but it’s pretty thin...need a pen light at just the right angle to see. I’m hoping there won’t be much image quality degradation with either of those. There were in such nice condition before, though! I wonder how hard it would be to access the rear of the front element on the 200. It seems like it might be easy to open up.
Hopefully this post is an effective reminder to all who read it. Do not leave your lenses in a hot car, especially outside of the trunk. You’ll end up with haze on your elements at best, and degraded coatings or separating cemented elements are a real possibility.
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