Mamiya C330: Bad shutter or bad film?

I got a major problem that just drives me mad. In short: It seems like my C330 correctly exposes Ilford Delta 100 film, but Fuji Velvia 100f comes out severely underexposed.

Please read the full story, I really wonder what the heck is going on here:

Two months ago, I got myself a Mamiya C330s with a 55 mm, and a 180-Super lens. I knew that these lenses can have inaccurate shutters, so I decided to do measurements of the shutters of both lenses. I used black-and-white film and a greycard to create a series of negatives using different shutter speeds. I changed both the f-stop and the shutter speed, so all negatives should have the same density.

I was very happy to see that for each lens, the negative densities were exactly the same. There may be differences of less than half a stop, which I cannot measure accurately, but this is good enough even for shooting transparancies. I checked the accuracy of the 1/4 second shutter speeds, by using a stopwatch timer. Both shutters turned out to be accurate at this speed.

I decided that I was ready to try some transparancy film: Fuji Velvia 100f. I shot a roll of Velvia and had it developed by my favourite lab. I was surprised to see that the film was heavily underexposed. I compared it to some 35mm transparances created using the same film, developed by the same lab. It looks like the C330 underexposed the film by 1 or 1.5 stops. I am 100% certain that the light meter was configured correctly, the indicated exposures were as I expected given the circumstances (bright, sunny weather). I did write down the used f-stops and shutter speeds for each frame (I always do that), and they really are correct.

This suggests that the shutter of both lenses is 1 or 1.5 stops too fast, at all shutter speeds. Is this what you expect to happen when a Mamiya TLR lens gets older??

I decided to do a second test to find out if the C330 really is underexposing the film. I used the following method: I know that the negative film used for testing (Ilford Delta 100) should have hardly any density when underexposed by 5 stops. I know this from my 35mm calibration tests. So, I used the C330 to underexpose some 120 Delta-100 by 5 stops and developed it in exactly the same way as I do my 35mm films, using the same developer. I noticed that the C330 negative was significantly denser than expected. Comparing it to 35mm calibration negatives, I found that the C330 seems to be overexposing the negative by about half a stop. This is opposite to what the C330 does to a Velvia 100f film.

Possible explanations I have been thinking of:

• The light meter is bad? No, I had it checked, and it is accurate.
• Lens shutters way off? B&W negative test suggest that the shutters are slightly over-exposing the film. They certainly do not appear to be underexposing it.
• The lab screwed up? Don't think so.. My 35mm transparancies always come out just right, processed by the same lab.
• The film is bad? Is it possible that my batch of Velvia 100f film is bad? The expiration date is somewhere in 2009, and it has always been stored refrigerated. Also in the shop. Also, the colors are fine and the grain looks good.

Is there any flaw in my testing method or reasoning? Anything I might have missed?

Thanks for any ideas you may have!

Dik

Perhaps the shutters are not consistent.

If you are talking about just a single roll of the transparency film, I would suggest a processing problem. Is the lab using separate machines/tanks for 35mm and 6x6?

John, Mount Vernon, Virginia USA

weasel: As a tried to explain in the post, the shutter speeds are consistent.

Anscojohn: Several other transparancy films were processed in one go. These were fine. I submitted a second roll of film, which is overexposed by 1 to 1.5 stops. I wonder if this one will come out right or not. If it does come out right, it means that I have have to shoot Velvia 100f at ISO 40 or so... :rolleyes:

An additional note: The other processed transparancy films were not from me, but from other customers of the lab.

Pardon me if this question is too basic, but are the tranparencies too light, or too dark?
Are you thinking in reverse when comparing the negs and transparencies?

If everything is consitent, just do a set of exposures with the transparency film, with the first exposure at around 100, then 80, 64, 50, etc. Which ever comes out correctly exposed, use that as your EI for that film with that camera. I do this when shooting transparencies; the differances in equipment isn't great, but slight deviations in a given meter, lens, shutter, processesor can add up. I rarely find my personal EI for transparencies varies more than 1/3 or 2/3'rds of a stop, but if you end up with an EI that's a stop slower (not unheard of btw) but is consistent and repeatable and gives you the results you expect, I'd be happy with that.

Peter

I just got the second transparency roll back from the lab. The frames that I have been overexposed by 1.5 stops have the correct density. This means that I will have to use Velvia 100f at ISO 40 or so, while Ilford Delta 100 should be used at ISO 100. Boy, this is weird...

I could just accept this as an unexplained fact, but It means I loose quite a bit of speed. Also, I hate the idea that there is something strange about my equipment that cannot be explained...

bdial: The transparancies are too dark.

I would try a different lab. Then if the film comes back the same, I would be looking elsewhere.

If the D100 appears a bit overexposed and the transparency film is way underexposed, my only conclusion is that the lab may not be using fresh chemicals.

Not many folks are shooting color transparency anymore so the smaller labs may not be doing daily test strips in their process lines.

Out of curiousity, who is processing the B/W?

The lab develops a lot of Velvia, and never had any problems.

But suppose that the lab is actually underdeveloping the transparancy film, and I am overexposing to compensate. Then it means that the film is currently being pulled. What effect would that have on the transparancy? Can one see if the film has been pulled or not?

Are You projecting the slides , or just holding them up to the light ?

Oh, I develop the B&W films myself. That's why I can guarantee that the 120 films are developed identical to the films that come out of my 35mm equipment.

takken,

Since you are doing the B/W and you have confidence in that process, I would strongly suspect the lab rather than the equipment.

Could be the lab hand processes the 120 stuff in SS tanks and it is not being processed properly (I worked for a premier lab in SoCal years ago and we did all the 120 transparencies in SS tanks).

Today, perhaps they can run 35/120 in the same machine but my local lab shut down the E-6 machine because of lack of business and the cost to keep the chems fresh and went to hand processing.

Anyway, I would continue testing B/W in the camera with different films to be sure you don't have an intermittent failure in the camera. This will give you more data and confidence to reach the proper conclusion.

Just my .02,

I would also suggest it is a lab error of some sort, especially if you know your black and white processing well. Are they using a densiometer to check the transparencies? I would think if the shutter speeds are a full stop or more faster than normal, you would hear it, especially in the slow speeds.

Rather than jumping on the lab first thing I would consider the testing methods by the photographer.
It is common for b&w & slides to have very different EI's.
Testing shutter speeds with a stopwatch? Come on now.
Your b&w density may be consistent, but the question comes to mind what are you using to determine density? Eyeball or densitometer?
Transparency film has far less latitude than B&W. If you're getting good shadow detail with the b&w then I would suggest that your exposure/processing is good, but your EI isn't what you think it is. Or you may be over developing a bit.
If you're getting historically good results from the lab that should be a clue of some sort shouldn't it?

Leaf shutters slow down with age (overexpose), if anything. The camera is not psychic, so it will do the same thing whatever film is in the camera. One of the film exposure/processing combinations is wrong. You are using the same meter for 35mm and 120?

Benjiboy: I examine them using a light table. I showed the transparancies to a professional slide scanning dude, and he agrees with me overexposing by 1.5 stops.

Fred: The lab uses machine processing (they develop about a dozen films a day), the process is calibrated on a regular basis.

JRJacobs: I use a quality spotmeter to determine neg density. It is just accurate enough to see differences of half a stop. But that's enough.

John Koehrer: Yes, I know that B&W films can have different EI's, depending on the development method and equipment used. I also know that, when I underexpose a B&W film by 5 stops and develop it using my standard developer, I get hardly any negative density. This is when using my 35mm camera, which is known to consistently produce perfect Velvia slides. Based on this knowledge, I determined that my 6x6 equipment leads to slight overexposure of B&W negatives, using the same development procedure. I think I can say this because the negatives that have been underexposed by 5 stops are clearly denser than I expect them to be. In any case, they are certainly not too thin! If anyone disagrees with me, please tell me!

Grahamp: Ok, this makes my situation even more strange. I use a built-in meter for 35mm and a handheld meter for 6x6. Both meters yield about the same values, within half a stop anyway.

Here is a good test that might shed light on things. Shoot a roll of Velvia in your 35mm camera, but meter it with your handheld meter the same way you do when shooting the Mamiya - worth checking for sure. With Velvia, 1/2 stop can cause quite a difference in exposure.

Sounds like a compounded error - the Mamiya has a slow-ish shutter, and the exposure meters have a relative error in the same direction.

The solution is simple... change the lens and see if the results are the same. If they are it's the lab, if not, it's the shutter.

See your shutter is built into the lens not the camera. So a new shutter is easily enough to change. The real beauty of these cameras, hey?