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Shutter speeds - wow! and yikes!
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PostPosted: Fri Feb 11, 2011 8:23 am    Post subject: Shutter speeds - wow! and yikes! Reply with quote

The shutter speed tester recently arrived and I have just started doing tests on my leaf-shutter folders and TLR (I'm not sure if the tester will work a camera like the Pentacon Six, that has cloth curtains close to the film surface - I don't want to wreck the curtains)

Anyway. my initial tests were both astonishing and scary.

The Welta Perle 6x4.5 folder from the early 30s with a Compur shutter, that I picked up for $20 or so, turns out to be accurate to within 10% or less all the way from one second (actual 1.1s) to 1/100s (actual 1/95). But at 1/250s the readings were 1/166, 1/142 and 1/175, so it seems to be about half a stop out.

The 1970s Mamiya c220 is a different story. It seems to be almost a stop slow all the way from 1s (1.4) all the way to 250 (1/125 actual) and the 1/500 only clocks in at 1/169! At least a one-stop error is easy enough to compensate for (meter for half the film's true ISO)

I guess the Mamiya lens has been heavily used by a pro and the springs have weakened over the years, while the Welta has had comparatively little use and so its springs are still in almost factory-new condition despite it being 75 years old.

In both cases, though, the very highest speed seems to be in fantasy land. This may be normal for shutters which don't have a separate high-speed train or for the highest speed on the slow train. My super-ikonta is 2/3 stop short of the stated speed at 1/250s, but when I switch to the high-speed spring on 1/500 it produces an acceptable 1/400.


PostPosted: Fri Feb 11, 2011 9:36 am    Post subject: Reply with quote

Barely anybody ever reached the nominal top speeds on mechanical shutters- these were usually already off by the permitted 10% on new cameras.

Springs don't wear or weaken - at any rate not under conditions that don't shatter or melt the shutter casing as well. Old shutters mostly suffer from dirt and gummed-up grease or oxidation. Sometimes they have warped (due to impact or over-tightening on the mount) or were damaged in poorly executed previous service attempts. Maybe one in a hundred will have worn bearings - but that is rare even in professional cameras, as the transport mechanics of most medium format cameras wear out long before the shutter, I've only ever seen worn bearings on Hasselblad and Mamiya lenses from motor-driven studio use.


PostPosted: Fri Feb 11, 2011 9:42 am    Post subject: Reply with quote

Thanks for that information. So if I could get someone to service the Mamiya lens it would probably go back to what it should be? Trouble is, the cost of the service is likely to be more than the lens is worth ... but then one good photo would make it worthwhile. A bit of a conundrum.


PostPosted: Fri Feb 11, 2011 2:45 pm    Post subject: Reply with quote

I have same experience than you have Paul.

Most of old folder even if cla'd by best service man 1/500 is maximum 1/225
I really not exciting about to fix all, I just used them on measured speeds and they are works well even with slides.
If a camera has at least 1/125 I am fine with that , due usually I used them above F8.

I think P6 will be measurable too just put box to lens mount side and light throw from back with a desktop table lamp.


PostPosted: Fri Feb 11, 2011 3:04 pm    Post subject: Reply with quote

Yes, the Welta seems to have been a really good bargain. I'm a bit disappointed with the C220. I may also need to refine my technique measuring the speeds to ensure I'm not getting to big an error on the highest speeds.


PostPosted: Fri Feb 11, 2011 3:13 pm    Post subject: Reply with quote

Hey Paul,

My apologies if I missed an earlier thread where you discussed the purchase of your shutter speed tester. I'm curious, which one was it you bought, and do you think it was a good value?

Since I do repair cameras and lenses on occasion, this is one tool that I think I should probably add to my collection.


PostPosted: Fri Feb 11, 2011 3:32 pm    Post subject: Reply with quote

I bought it from Attila's store, it's Florin's version. I've not used the software before, so I am getting used to it. Getting the light source right seems to be critical and I'm having a bit of trouble interpreting the graphs at the fastest speeds but the results I am getting are very consistent. - here's a set I took earlier from a Nettar (not sure the 1/250 is right, might be experimental error).

1/250 = 1/100s 1/172 1/102 1/125
1/100 = 1/70 1/99 1/86
1/50 = 1/40 1/40 1/35
1/25 = 1/20 1/19 1/20
1/10 = 1/6 1/7 1/7
1/5 = 1/5 1/5 1/5
= 0.6 0.6 0.6
1s = 1.23 1.27 1.06

With the C220, two sets of readings both showed it was pretty consistently one stop wrong, which is really essential information for getting good results from it. So it's likely to save me an awful lot of wasted film and processing costs (unfortunately, I have 10 rolls being processed right now which are presumably all a stop over-exposed)

I couldn't see the point of spending $200 on a Pentax spotmeter and then not knowing for sure what the shutter speeds are, for want of another 20 bucks or whatever on a tester. I would say it has already proved itself to be an excellent investment for me, even though I've only been using it for a day.

I don't plan to try to correct the speeds, just to adjust my meter to allow for them (where they are consistent) and I'll also avoid going to the top speeds unless I get really consistent readings for them (e.g if the C220s 1/500 turns out always to be 1/250 I will use it as that).


PostPosted: Fri Feb 11, 2011 7:30 pm    Post subject: Reply with quote

Paul, use a simple desktop lamp above camera body that is strong enough to measure speeds. Cold light source is better perhaps like energy saver bulb. Measure first your most accurate 35mm SLR usually they speeds are spot on. Get practice with it how can you read diagram, after all you will be sure about old folders too.


PostPosted: Fri Feb 11, 2011 7:44 pm    Post subject: Reply with quote

Thanks, Attila, that's a great idea about using the 5D to practice on. I've got a desk lamp somewhere, too.

Oh, hang on! I can't open the back of a 5D Embarassed Rolling Eyes it'll have to be the Leica.


PostPosted: Fri Feb 11, 2011 8:02 pm    Post subject: Reply with quote

Smile any praktica , nikon etc ? any newer SLR is just fine.


PostPosted: Fri Feb 11, 2011 8:25 pm    Post subject: Reply with quote

PaulC wrote:
Oh, hang on! I can't open the back of a 5D Embarassed Rolling Eyes


Thank you for that, although I did have to clear my computer screen from the coffee that escaped me when I read it Very Happy


PostPosted: Fri Feb 11, 2011 8:29 pm    Post subject: Reply with quote

Laughing Laughing Laughing


PostPosted: Sat Feb 12, 2011 12:24 pm    Post subject: Reply with quote

The Pentacon Six can't be tested by putting the device where the lens goes because at speeds above 1/30 the shutter works by running the two curtains at the same time with a gap between them. This means that at 1/1000s it takes about 1/34s between the shutter starting to open on one side and closing on the other, though as the slice of light moves across, each grain is only exposed for 1/1,000s (I know the time it takes for the shutter to run because all the higher-speed measurements taken from the front of the camera produced timings of 1/34).

In order to measure some of the shutter speeds on the P6, you need to have the measuring device flat against the film plane, acting like a bit of grain. I did this by cutting out cardboard the same shape as a piece of 120 film, making a tiny hole for the sensor to "see" through, taping the sensor to the back of the cardboard and the cardboard to the camera body.

It's likely that the device is starting to give slightly false readings at the highest speeds, because of the width of the sensor - it's not big but it should be the size of film grain to get exactly the same exposure as film.

My recently serviced Pentacon Six had correct timings from 1 second to 1/125. At 1/250 the device recorded 1/229, at 500 it was 1/330s and at 1000 it was 1/560s. I don't know if this is because the shutter really is slow or if the maybe 3mm wide hole it was recording through.

It takes 1/34s for the shutter to open and close across the whole 60mm width of the frame, so it will take about 1/600s for it to pass across a 3mm gap. At high shuitter speeds the lag between one side of the sensor and the other will be appreciable, meaning my high shutter speeds will be closer to the stated speeds than the test results suggest.

This is only going to be a problem with focal plane shutters, and probably only with the medium format cloth kind. Even with those, it seems measurements of up to almost 1/250 are possible before the error becomes significant.


PostPosted: Sat Feb 12, 2011 12:31 pm    Post subject: Reply with quote

Not really a problem if you shoot on b&w or negative film, quite a disaster on slides. Wink


PostPosted: Sat Feb 12, 2011 12:54 pm    Post subject: Reply with quote

I'm planning to drop colour film and stick to B&W and colour slides, so I need to know what the cameras are doing.

I took some very carefully metered B&W with the Mamiya before I knew it was a stop off. It will be interesting to see if what comes back from the processor is any good. I screwed up my last lot of Ilford Pan-F 50 by getting condensation into the film it'll be sad if my next batch is wrecked by exposure problems. Tri-x 400 can take a stop of over-exposure, they say, I'm not so sure about Pan-F.


PostPosted: Sat Feb 12, 2011 4:39 pm    Post subject: Reply with quote

many thanks Paul for detailed description about P6 I thought it is same than a 35mm SLR.


PostPosted: Sat Feb 12, 2011 4:58 pm    Post subject: Reply with quote

That horizontal curtain shutter in the P6 is actually very interesting, and so is the fact I have found out how long it takes to run from one side to the other. It means I should be able to effect Lartigue got in his famous car photo that I explained here http://fotoblogzone.com/2011/01/20/lartigues-wheel/

I will have to turn the P6 clockwise by 90 degrees, so the shutter runs from top to bottom and then pan for at least 1/34s while shooting to allow the shutter to complete its run.

It's bizarre, isn't it? It takes a P6 1/34s to take a photo at any shutter speed above 1/15th, even at 1/1,000s.

Someone - was it Man Ray? - used this property of cloth shutters to photograph a couple wound round each other like the DNA spiral (they were standing on a fast-moving turntable).


PostPosted: Sat Feb 12, 2011 5:38 pm    Post subject: Reply with quote

Yes, right pretty bizarre.


PostPosted: Sat Feb 12, 2011 5:38 pm    Post subject: Reply with quote

I didn't know that the P6 had a focal plane shutter, I love that effect in the Lartigue photo and I can't remember who did it but someone did similar with a helicopter, making the blades appear twisted. Getting a good medium format camera and trying out a focal plane shutter are on my photographic to do list.


PostPosted: Sat Feb 12, 2011 9:01 pm    Post subject: Reply with quote

The helicopter was from a DSLR, I think.


PostPosted: Sun Feb 13, 2011 3:18 am    Post subject: Reply with quote

William wrote:
I didn't know that the P6 had a focal plane shutter, I love that effect in the Lartigue photo and I can't remember who did it but someone did similar with a helicopter, making the blades appear twisted. Getting a good medium format camera and trying out a focal plane shutter are on my photographic to do list.


Well, there are others out there besides the Pentacon. The Bronica S2a and EC or EC-TL are great square-format outfits. Then there's the king-of-the-hill, in my opinion, the Pentax 6x7. Also, you can use an old Graflex Pacemaker Speed Graphic with a roll-film back for focal plane shutter work.

I've accomplished this same sort of twisting effect you mention with 35mm. First time I saw it in one of my images, I didn't know what caused it, and it took a bit of pondering on my part to realize what had occurred. In my case, it was a combination of rapid subject movement and not panning fast enough that led to the image being distorted as the shutter slit traveled across the focal plane. It was a race car, as it so happened. I think that it would be difficult to accomplish this with anything moving slowly or standing still.


PostPosted: Sun Feb 13, 2011 5:20 am    Post subject: Reply with quote

You have to have rapid movement. The helicopter was on the ground but its rotor was turning (if I remember correctly) as the shutter went across the rotor was almost keeping up with it so the blades ended up with the most bizarre shape.
The speed everything is moving at (including panning) and the direction the shutter runs in is critical to the result. A horizontal shutter usually just stretches things out, like a wide-screen monitor, a vertical shutter with horizontal movement creates an angular distortion, a leaf shutter doesn't do this at all.
The time the shutter takes to complete its action will also be vital, so a really fast electronic shutter will have a much wider slot that the light comes through than an old cloth shutter. I'm pretty sure that to maximise the effect you want the narrowest slot you can get (fastest shutter speed) and the slowest-running shutter (1/34s should be pretty good for that). The better the object fills the frame, the more apparent the effect will be though the angle of distortion will be independent of the magnification.


PostPosted: Sun Feb 13, 2011 5:25 am    Post subject: Reply with quote

Great idea!

I have a 3x4 Speed Graphic fitted with a 2x3 back in a "portrait" configuration which should be perfect for this trick.

Now I have to find a turntable and a couple to get to dance on it !


PostPosted: Sun Feb 13, 2011 5:35 am    Post subject: Reply with quote

Or put some objects on an old record turntable, or visit an air show or race-track. Just think about which way the shutter runs. The turntable trick may have used a shutter adjusted to take an extra-long time to do its trick, apparently some people did have their cameras adjusted in the 20s and 30s in order to maximise this effect.

After some more thought I have concluded that if the full shutter run takes 1/30s, than for 1/60 the second curtain must start running when the first one is halfway across. As the film gate is 60mm wide, this means a 30mm wide slot. For 1/125 the slot must be 15mm wide, for 250 it is 7.5, for 500 3.75 and for 1/1,000 less than 2mm

If the sensor is getting its info through a 2mm hole, then the error at 1/500 would be 1/3 of the timing, and at 1/1,000 it would be equal to the time. My actual results, of 1/500 = 330 (x3/2 = 495) and 1,000 (1/560 x2 = 1,120) suggest that the shutter is probably close to right even at its fastest speeds.