[Kmier]

Hi, All,

New to this forum; I bought a 645 with a 45mm f2.8 to play around with film once again. I’ve shot two rolls of Ektar 100 through it with dismal results - every photo is drastically underexposed. My scenes are all in reasonably sunny settings, various subjects. I know I have the ISO set right and the exposure compensation is at ‘0’. Fresh batteries, and everything seems normal.

I don’t see a ton of threads describing this issue. What should I look for to resolve this?

Thanks in advance.

[Alex645]

Hi, All,

New to this forum; I bought a 645 with a 45mm f2.8 to play around with film once again. I’ve shot two rolls of Ektar 100 through it with dismal results - every photo is drastically underexposed. My scenes are all in reasonably sunny settings, various subjects. I know I have the ISO set right and the exposure compensation is at ‘0’. Fresh batteries, and everything seems normal.

I don’t see a ton of threads describing this issue. What should I look for to resolve this?

I've owned a 645 since they were new in the 80's and mine has always underexposed. It works really nicely for slide film, but not what you want for negs.

I think it has a lot to do with metering pattern and that the meter is overly influenced by bright skies or highlights. I would recommend using one roll just for tests.
a) Shoot half a roll of Ektar 100 of a neutral evenly lit low contrast subject such as brick wall. Avoid anything that has bright highlights and dark shadows. Try -1EV, N, +1EV, +2EV, and +3EV. Then find a landscape scene with a bright sky, preferably high contrast with some clouds and a few deep shadows. Bracket your exposures the same.

It is possible that your light meter needs recalibration or that you accidentally had it set to some -EV value, but I doubt it. In general, I will shoot negs at +1EV or rate an Ektar 100 at 50 ISO. You can also use another camera that has consistently good exposures to compare with your 645 to see approximately how far off it is and how much compensation is required.

BTW: Are you sure the lab isn't underdeveloping (too little time, exhausted developer, too low temperature) your Ektar? Does the edge numbering look dark with a clear orange stained base? Or does it look a bit faded?

[photoptimist]

Step 1 might be to troubleshot the exposure system & camera.

1. Is the meter reading correctly? (Compare the exposure settings the 645 wants to use with those that another known-good camera is metering(

2. Is the Aperture mechanism of the camera lens working properly? (dry-fire the camera at different aperture settings while watching the lens from front to see if it closes down the right amount.)

3. If the shutter working properly? (This is a bit harder to accurately test so do the first two tests first.)

[Kmier]

Thanks for the kind reply. I will take your advice and sacrifice a roll of both Ektar 100 and Portra 400.

I have had good recent success with ‘The Darkroom’ online for developing my film, and I’m just thrilled that my old Minolta SRT-201 still cranks out great pictures after all these years. The edge numbers on the 120 film are dark and clear, so I’m pretty sure that I’m the problem and not the lab.

Interesting that you use ISO 50 and +1EV for the Ektar. I will determine how close I get to that setting after I run my tests.

Last question: Can these old light meters actually be re-calibrated? Is this something I might be able to do myself, or is it beyond the skills of a handy person? I do look forward to eventually getting some good, solid medium format photos!

[Kmier]

Photoptimist:

Thank you - good steps to take. I will compare against my Minolta 35mm with a lens with a similar field of view.

Looking forward to sorting this out!

[Alex645]

2. Is the Aperture mechanism of the camera lens working properly? (dry-fire the camera at different aperture settings while watching the lens from front to see if it closes down the right amount.)
3. If the shutter working properly? (This is a bit harder to accurately test so do the first two tests first.)

I thought of this, but I would expect the aperture not closing down enough and therefore over exposure issues, not under.
Same with the shutter possibly on the slow side, thus over exposing, but not too fast causing under.

I will take your advice and sacrifice a roll of both Ektar 100 and Portra 400.

Last question: Can these old light meters actually be re-calibrated? Is this something I might be able to do myself, or is it beyond the skills of a handy person? I do look forward to eventually getting some good, solid medium format photos!

I would suggest just the Ektar as a 100 ISO emulsion has less exposure latitude and thus show more effect of over or under exposure. The Portra 400 is more forgiving and it will be harder to see exposure errors.

Yes, I am sure the light meter can be re-calibrated, but it is not worth the time finding someone competent to do it, or the cost. What you can do yourself if you don't want to use an incident light meter or another more accurate reflective one is as I mentioned....run your tests and then leave your EV compensation to the + amount needed. It has worked for me and if it's the shot of a lifetime, just bracket your exposures for insurance.

[Kmier]

Well, I confirmed that the internal light meter is a direct match with a known good camera’s meter, so I’m confident in the accuracy of the 645’s meter.

But, when I dry-fire the shutter with the film back removed, it appears that it only fires at 1/1000, regardless of what setting (with random aperature set on lens). I tried 1/60 and it’s the same speed as 1/1000 (at least to my eye). It will do a bulb setting. With the lens set to ‘A’, the red led info says ‘1000 f16’, but will constrict the aperature down to f22 when the shutter is fired.

Does this all sound abnormal? I’m thinking that my shutter is stuck to 1/1000 when taking pictures in aperature priority mode, as I have been doing for my first two rolls. Is there anything else I can try? Sad to think that my camera might be a dud.

---------- Post added 08-26-18 at 07:48 AM ----------

I will add that when the lens is NOT set to ‘A’, I get the proper aperature response when test firing, but again, I see no change in shutter speed between m1000, m30 or 60 settings.

[Alex645]

But, when I dry-fire the shutter with the film back removed, it appears that it only fires at 1/1000, regardless of what setting (with random aperature set on lens).

That is normal. Note page 14 on the owner's manual:

http://www.pentax-manuals.com/manuals/medformat/645.pdf

[victormeldrew]

If developing your own film you can of course correct the issue in post (as it were), and I would expect a high quality lab to be able to do the same if you ask.

[Kmier]

If developing your own film you can of course correct the issue in post (as it were), and I would expect a high quality lab to be able to do the same if you ask.

I’ve actually isolated the problem down to an issue with the aperature priority mode. Watching from the front of the lens during an f2.8 exposure, I notice that the aperature moves to somewhere in the f16 / f22 range during exposure (obviously creating unsalvageable photos). I don’t seem to have that happening in either manual or shutter priority modes. I’m not yet developing my own film / scanning yet, but that may come.

I have a couple of test rolls going out tomorrow for development. I can live with working this camera in manual mode if I have to.

Thanks!

[Alex645]

I’ve actually isolated the problem down to an issue with the aperature priority mode. Watching from the front of the lens during an f2.8 exposure, I notice that the aperature moves to somewhere in the f16 / f22 range during exposure (obviously creating unsalvageable photos). I don’t seem to have that happening in either manual or shutter priority modes.

Kudos for isolating the cause. That's a new one I've not heard of before. The next mystery might be to see if this is an issue with the lens or the camera?

And PhotOptimist was right on suggestion #2.

[Kmier]

Kudos for isolating the cause. That's a new one I've not heard of before. The next mystery might be to see if this is an issue with the lens or the camera?

And PhotOptimist was right on suggestion #2.

I suspect it’s the camera, because it stayed wide open (when I set the lens to f2.8) during manual and shutter priority. I made notes during the test, so I’ll report back once I get the film developed. Thanks!

[torashi]

I tested a Super A a few days ago with the same weird problem. It would shoot at 1/1000 whenver it felt like. Then it would meter and shoot normally. There was definitely something off with the electronics.

[Kmier]

While waiting for my test photos to be uploaded - I noticed in the manual that “the depth of field cannot be confirmed while the lens is set to “A”.” When my lens is set to “A”, the stopdown lever will close the aperature completely, contradicting the statement in the manual. It’s also true with the lens removed - the lens tab will close the aperature completely while set to “A”. [I don’t have any other lenses to compare functionality].

Would someone be able to confirm whether I might have a lens issue instead of a camera issue? Thank you in advance.

[Alex645]

in the manual that “the depth of field cannot be confirmed while the lens is set to “A”.” When my lens is set to “A”, the stopdown lever will close the aperature completely, contradicting the statement in the manual.

Would someone be able to confirm whether I might have a lens issue instead of a camera issue?

What the manual means is that when the lens is set on "A", and then you depress your depth-of-field preview lever, it will close the lens down to its min. aperture such as f/22 on your 45mm prime. If you had f/8 set in the camera, it won't show you f/8 with the d-o-f preview lever.

HOWEVER, if you put the false back onto the camera (or had film in) and looked at the lens with a slow shutter like 1/2" @ f/8, you should see it closing down to f/8, not f/22, with the lens set on A.