Shutter Speed Check...

[Kuzano]

I just acquired two lenses. One a Rodenstock Sironar N 210 in Copal 1 shutter and two... Rodenstock Sironar N 135 in Copal 0 shutter. While, I've always been vaguely aware that shutters do not often shoot the listed speed, I've never had a shutter checked for speed. I've presumed that film latitude, meter variances and other factors took care of some slack, although I know how such variances stacked up in one direction might have a negative effect on exposure (HAH!!)

However, I wonder how much of a factor this is, and how common it is to have a table of corrected shutter speeds for each shutter in your possession. Having seen camera's come back from service with a list of actual shutter speeds, it makes me wonder how likely it is that a service on a shutter can achieve listed speeds, or simply come back with a correction table.

The lens board on each of these lens has a table with actual speeds. They are:

Copal 1
1=1
2=2
4=4
8=8
15=15
30=30
60=52
125=108
250=216
400=300

Copal 0
1=1
2=3/4
4=3
8=8
15=20
30=20
60=60
125=125
250=250
500=450

Interesting to me that the big shutter is so correct on the slow speeds and quite off on the 1/400th, while the Copal 0 is the opposite.

How many of you concern yourselves with this aspect of your equipment. It seems that one could spend some time chasing the "perfect" shutter with all speeds matching the listed scale, as opposed to having a corrected table of speeds for each shutter. How big a factor is this?

And of course, then there is the aperture???? Should an aperture be re-scaled every time a new set of lens cells is screwed in?

[bspeed]

I have made a corrected list, that it taped to the lensboard/lens cap :) doesnt hurt to know, even if it's only say 1/3 or 1/4 stop.

[mandoman7]

Kuzano,

Its very worthwhile to purchase a shutter tester if you will be using many lenses, or trading. Calumet has one that's similar to one I purchased long ago. It has paid for itself many times with regard to not wasting film.

Using a tester is hugely informative as to what to expect from your lenses. Almost all of lenses that I've tested are surprisingly off by 10% at most speeds. This won't show in your negatives, but its good to know if you're testing film and using a densitometer. A lot of my old compurs sounded good, but were 20-30% off at medium to fast speeds.

When I don't have my tester handy, I've found the 1 sec. setting to be informative. Check your watch to get the cadence of seconds and then fire off your shutter to see if its in step. You can tell if its 30% off with this method. I don't really know, but my sense is that if its working at 1 sec. then the others should will likely be OK.

Your tester will also show you that your first release will not be at the same speeds as the next two or three, reminding us that we should fire a blank or two to loosen the blades before shooting the film itself.

The charts you get from the technician are good, but for how long and under what temperatures are they good for? How confident will you be with them a year later on that windy hillside? If you don't buy a tester, find someone who has one. Go thereafter with confidence.

My opinion of course.

JY

[Captain_joe6]

I'm taking a course in studio lighting right now, and its amazing how much 1/3 of a stop can affect things. E6 and digital have such narrow latitude that you've got to be right on the money or you'll start to lose some detail somewhere.

B&W film, on the other hand, has much, much more latitude, so 1/3 of a stop is no big hurdle. If you want to be really finicky, then figure out the stop value of the differences, and attempt to adjust your aperture to correct.

[Kuzano]

I can see the advantage of the list on the lens board, or with the lens. So far it sounds like knowing the corrections is less trouble than expecting shutters to be at listed speeds across the board.

I've considered the calumet tester, since I wondered about how long a list might be good once tested.

And, I shoot color, so the narrow latitude is an issue.

Thanks all.

Kuzano

[Glenn Thoreson]

I use mostly ancient shutters. I test all of them and tape actual speeds to the board if off by more that 1/3 stop. The larger the shutter, the more likely the high speeds will be slower. Mass vs kinetic energy or something. The actual speed can easily be worked around with aperture settings if need be. The critical part is consistency. You can't work with something that changes it's mind every time you click it. Don't forget the fact that speeds will slow down with cold temperatures, too. They can also speed up if it's really hot. Nothing is certain in this game. :D

[mandoman7]

I'm taking a course in studio lighting right now, and its amazing how much 1/3 of a stop can affect things. E6 and digital have such narrow latitude that you've got to be right on the money or you'll start to lose some detail somewhere.

B&W film, on the other hand, has much, much more latitude, so 1/3 of a stop is no big hurdle. If you want to be really finicky, then figure out the stop value of the differences, and attempt to adjust your aperture to correct.

So you're agreeing with me that a tester is a good idea, right?

JY

[Ivan J. Eberle]

I take it you didn't test these yourself, or have them calibrated, you're just going by someone else's reckoning? Do you know how they arrived at these speeds? If they didn't use a good technique or clean the shutter or if they've sat awhile since and the grease has further congealed, those numbers may have no significance anymore.

If the numbers are still valid, it's less than a 1/3 of a stop off on your first shutter, and only on the very fastest speed. If still true, that one's a definite keeper.

#2, the Copal 0 is wonky in the daylight speeds you might be using all the time whenever stopped down... as if it has a lot of wear in that range, perhaps? Or, maybe it's just sticking in that range for some reason, like old grease.

I'd suggest either having them CLA'd and professionally calibrated, or do like I did and surf the internet for a tutorial on how to make a sub-$20 USB/Photo-transistor tester that uses freeware like Audacity for the graphing.

[Kuzano]

I take it you didn't test these yourself, or have them calibrated, you're just going by someone else's reckoning? Do you know how they arrived at these speeds?

No, not my testing or numbers. And, I wouldn't be surprised that these lens/shutters have been stored long enough to get them re-checked, or better yet, CLA'd.

The cosmetic condition and optics are excellent plus, and there is no wear on the shutter surfaces, or rims of the lens elements. No signs of cleaning marks or coating blemishes. They appear to be well worth some expense to make them reliable.