- Joined
- Nov 29, 2006
- Messages
- 8
- Format
- 35mm
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:
Is there any flaw in my testing method or reasoning? Anything I might have missed?
Thanks for any ideas you may have!
Dik
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
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.
