Is my lens bad?

jmal · Sep 15, 2008

Let me preface this by saying that I don't have prints scanned and I'm not sure it would be apparent in a low quality scan anyway. So, here's my problem. I have a Mamiya M645 1000s that I have owned for 7 months, but have run very little film through. Perhaps 6 rolls. I never can get what I consider to be a sharp image, even at 8x10. Some prints are just barely tolerable, but most are clearly not in focus--anywhere. Even when shooting objects at a distance and the focus is set to infinity. Keep in mind that I am shooting static objects handheld at shutter speeds no lower than 1/125 on an 80mm lens. The lens is one of the later 80mm models. At first I thought it was just the lack of DOF associated with MF. However, I have seen plenty of photos in MF that have reasonable DOF. And please don't say "it's not Zeiss glass" because Mamiya lenses are perfectly capable of getting sharp images. Any thoughts? I am going to try to borrow a friend's lens to see if the results differ, but I figured I'd ask here too. Oh, one more curiosity. I printed one photo at grade 2 and it looked adequate. Then, I printed it at grade 1 to get more tone in the sky and the G1 looks OOF while the G2 appears more focused, though not super sharp. Thanks.

Jmal

Larry.Manuel · Sep 15, 2008

I don't know that camera, but I have been thinking about optics for 40 years. Borrowing a friend's lens seems a great way to trouble-shoot the problem. I bet the lens is normally capable of razor-sharp negatives. Your method of shooting at infinity is a good one, too. The viewfinder screen may be out of place - although you have wisely bypassed that cause by your infinity method.

Is it possible that the lens isn't in the designed location? - i.e. slightly ahead with a mis-fitted lens attachment flange, for example. It must be small distance if that is the problem.

Perhaps the lens requires an overhaul. I can imagine something being amiss there, without knowing exactly what it might be.

Looking at the negatives with a magnifier should remove any doubt of sharpness. With my Rolleicord, on ACROS film, I photographed my daughter's boyfriend, on his bike, from about 12 feet away. I could see a myriad of his leg hairs on the negative, and these didn't survive [low-cost] scanning and digital printing.

Is it possible that the film isn't in the correct place? A few thousandths of an inch error and images would not be sharp. If you could borrow a ground glass, and hold it against the film guide rails, that will show if the lens is forming the image in the correct plane.

I imagine that when you solve the problem, the negatives will be stunningly sharp. My best wishes.

jmal · Sep 15, 2008

LM--the lens has no other attachments and is mounted correctly. As for the film location, there is no other place it can go. It's a pretty simple mechanism. And, the film is wound snugly againt the pressure plate, so it should be flat. We'll see what another lens changes, if anything. Thanks.

JHannon · Sep 15, 2008

I would double check the seating of the focusing screen under the finder. It may be not seated fully and locked in place.

jmal · Sep 15, 2008

I will double check it, but I believe it is seated well. It sort of "snaps" into place. It's definitely worth checking, but how about the shots at infinity? They should have something in focus.

phenix · Sep 15, 2008

Did this lens pass a CLA before you used it? If yes, than it is very possible that an element was mounted reversed. Usually it is the case of a quasi-symmetric element. I’ve bought once a 50/1.4 lens (35mm format) that showed the same symptoms you are explaining here, including the error to focus at infinity. I took it apart, and reversed an element that looked quite symmetrical, but of course wasn’t. After this operation, my lens worked perfectly. Just a suggestion.

Anyway, as said before, if your lens doesn’t focus at infinity, your troubles are not from the focussing screen. Leave it as is, don’t introduce another variable in this equation.

bnstein · Sep 15, 2008

The quickest road to Rome=get another lens: if this will focus sharply on your negative (forget the print) you can be happy about the body and the mount. If not, then try a different back as the next step. I have seen a dropped camera (landed nose down) where the mount snapped in nicely but the flange was very slightly buckled. This was evident on inspection of image on ground glass (actually the poor man's trick of scotch tape across the film gate) as only a part of the image would come into focus.

Very frustrating for you because this camera is quite capable of excellent results.

jmal · Sep 15, 2008

Thanks for the advice. As for the CLA, it could have been done before I bought it, but I have no idea. I bought the kit from KEH in EX+ condition, so it all looks good. I don't see any evidence of damage to the body or mount. We'll see how another lens works out. If it looks good, I will just geta new lens. They are probably cheaper than sending a camera for repair.

elekm · Sep 16, 2008

You could always check the collimation of the lens using an SLR and a telephoto lens. It's fairly simple to do, and it will tell you a lot about whether the Mamiya lens is sharp at infinity.

When checking collimation, the lens should reach its sharpest point when it's at infinity.

Also, is it possible for you to try that lens on another body?

Ian Grant · Sep 16, 2008

Get the camera checked out, it is possible the screen is off register. I have a 1000s and a 645J and I noticed the 645J body wasn't sharp at wider apertures. I placed a ground glass screen across film plane with the camera back & shutter open and cross checked with the focussing screen and it was out of register, so it was corrected and was fine afterwards.

Once it is sfixed make sure that you use the MU - mirror up - option whenever you use the camera on a tripod, this prevents mirror slap and the resulting images are significantly sharper.

Ian

Kevin Kehler · Sep 16, 2008

This might sound like a stupid suggestion but I had noticed a significant drop in sharpness of prints about a year ago. I thought that perhaps the lens elements were loose or the focus screen was off; turns out one of my eyes made a significant change in prescription strength and since I used that eye to focus, the pictures were off. My eye doctor said these changes can happen suddenly or gradually. A $100 visit to the optometrist might save a $500+ camera repair if you haven't had your eyes checked recently.

Andy38 · Sep 16, 2008

Kevin , it's not a stupid suggestion : I have solved a focus problem with -3d eyepiece correction lenses , because I don't like to use glasses while photographying .

An other suggestion : many lenses don't give sharp images at full aperture and it's better at f:5,6 and more .
Perhaps some tests at several apertures could give some information...
(I say that , but I have a 50mm Sekor RB67 C lens which is bad at f:4,5 and also bad at f:8...)

noumin · Sep 16, 2008

I have nothing to offer than a few stupid questions and suggestions :

- If you use an "N" Type lens you should be ok with DOF. The DOF-Scales on the older non "N" lenses
were way to optimistic.
- Do you use a waistlevel finder and if so, do you use the loupe for focussing ?
- You're not using 120 film with a 220 back ? I don't know if this is technically possible but who knows.
- Just for comparison, use a tripod or put the camera on a wall or chair or what's available
for a shot, and then mirror up, cable release and see if this helps.
- Check if the groundglas is properly seated.
- Do the negatives actually appear sharp ? It seems you make your own enlargement, it could as well be, that
there is something going wrong there. And yes more contrast does make prints appear sharper.

jmal · Sep 16, 2008

Not my eyes--still 20/20 and I shoot a Nikon with a plain focusing screen rather than the rangefinder in the Mamiya, which makes focusing easier (and I have also shot at infinity with no sharpnes anywhere). Not the aperture--occurs at f8 and f16. It's a later N model lens. I use the eye level prism, not a waist level finder. Enlarger is fine for other formats and cameras.

Ian Grant · Sep 16, 2008

Before you do anything else check the lens focus like I suggested early. If you don't have a glass screen to put across the film plane then waxed paper used in cooking or tracing paper will work just tape it tight. Put the camera on a tripod focus on something using the normal screen/prism finder then fire the shutter on B and see if the image is sharp at the film plane.

Ian

jmal · Sep 16, 2008

Ian, how do I get the wax paper in/on the film plane. the body doesn't have a removable back, so the film plane is inside the body. Thanks.

Anscojohn · Sep 16, 2008

If the image on the ground glass looks sharp, it must be the ground glass or the mirror which is the culprit, it seems to me.

Shangheye · Sep 16, 2008

As a comment on your G1 and G2 difference, that could well be the contrast effect creating a "perceived" increase in sharpness. This is not real and is more about how the eye resolves images. Is the improvement of the sharpness perceptible in areas of continuous tone or are you perceiving it at the edges (more likely to be related to contrast increase?)

If it was me, i would set up a controlled test with the existing lens, set to infinity, and also close up, with an f-stop set two stops down from fully open on a tripod. I would then pay a visit to a shop with exactly the same film and set-up in camera and take a couple of pictures with a new lens, on the pormise to the shop that you want to check out the lens before buying it...if all the pictures are the same after development, then you may be looking at a viewing screen or maybe even a film plane issue...

Finally...are you sure the sharpness is not lost in the printing stage....?

K

jmal · Sep 16, 2008

Shangheye, the sharpness is on egdes and I agree with you that this is probably perceived sharpness due to contrast. Also, I'm in luck for testing because a friend works at a local store and I can try any of the bodies. lenses, and prisms for free. No explanations needed. Lastly, I don't believe the sharpness is lost at the printing stage but I will be trying a news enlarger lens tomorrow. That is the only variable at the printing stage.

Ian Grant · Sep 16, 2008

jmal said:
Ian, how do I get the wax paper in/on the film plane. the body doesn't have a removable back, so the film plane is inside the body. Thanks.

That's a very good point, it's about10 years since I tested my 645J - I had an unmounted focus screen and used that. It showed that the focus screen was significantly out on my camera.

As you can get your friends help get the store to have a look for you.

Ian

John Koehrer · Sep 17, 2008

Remove the insert & affix the wax paper to the approximate film plane on the film side of the body.
It's very common for lenses like this to have the focusing ring shift over time.There should be three set screws under the focusing grip. If any two or three have loosened it would allow the ring to shift. Most frequently when I've seen this the lens tends to focus more closely than indicated.

Is my lens bad?

noumin

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