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View Full Version : Weird finding about 14in Kodak Commercial Ektar~



pierre506
1-Jul-2014, 06:42
Deal all,
Please participate this thread if you have the lens, too.
Occasionally, I found my lens' real aperture diameter was different from my friend's.
The first picture shows the two lens apertures are in F45, but the diameters are different.
117588
117589
The aperture of the lens in No.5 Universal Synchro Shutter is obviously smaller than the lens in barrel.
F45:
Shutter aperture Diameter is about 7mm.
Barrel aperture Diameter is about 11.5mm.
F32:
Shutter aperture Diameter is about 10mm.
Barrel aperture Diameter is about 15mm.
F22:
Shutter aperture Diameter is about 13.5mm.
Barrel aperture Diameter is about 18mm.
F16:
Shutter aperture Diameter is about 19mm.
Barrel aperture Diameter is about 23mm.
F11:
Shutter aperture Diameter is about 27.5mm.
Barrel aperture Diameter is about 33mm.
F8:
Shutter aperture Diameter is about 38.5mm.
Barrel aperture Diameter is about 43mm.
F6.3(wide open):
Shutter aperture Diameter is about 52mm.
Barrel aperture Diameter is about 52mm.

The front and rear groups can interchange to each other.
The shutter barrel and the barrel's length without glasses are the same: 50mm.

I was totally confused about the apertures.
Help~

Kevin Crisp
1-Jul-2014, 07:38
I don't know if you are measuring the apparent aperture of the lenses (look down through the glass at the aperture, hold the ruler close to the glass and eyeball it) or taking the glass out and then making the measurement. You should be measuring the apparent aperture. I also don't know which lens is yours and which is your friend's.

That being said, I'd say the shuttered lens is pretty close to accurate. (f:45 = f:50; f:32 = f:35; f:22 - f:26, etc.) They seem to never come out perfect, and with less round apertures (like a Copal) estimating the opening is tough. The lens in barrell appears to be off, as you have detected. f:45 = f:30; f:32 = f:23, etc. By about a stop.

pierre506
1-Jul-2014, 07:46
Lens in the shutter(left) is mine.

I used a Vernier calipers to measure the size after taking off the glasses.

Kevin Crisp
1-Jul-2014, 08:33
Well then I'd say your friend has a minor problem and you're all set.

goamules
1-Jul-2014, 09:02
Hi Pierre,
I don't have an Ektar, but I do notice that many lens sizes, speeds, and manufacturing methods vary over the years, even though they are "the same design." Yesterday Mark Sawyer and I were comparing two Bausch & Lomb, Portrait Plastigmats. They were the same sized barrels, but the iris position and hood were different. Holding both lenses near a wall, one was a 15", the other 18" focal length. But again, the same size barrels (so approximately the same sized glass), and the same aperture/F-stop markings. The math would obviously show one slower than the other, but they were both "F5.6 Plastigmats."

I think the apertures were based on the bare, ("clean" in pilot lingo) lens before apertures were installed. In other words, the design was based on the engineering prototype. Each change, addition of shutters, etc., reduced the speed somewhat, but they didn't make a point of mentioning that in the advertisements. Seldom do I find any lens that measures it's advertised speed, they're always slower.

On measurement, make sure you do that with the front lens glass in place. That is the correct way. You have to look at the apparent opening of the iris, not measure the actual opening with the lens glass removed.

ic-racer
1-Jul-2014, 15:02
The barrel lens looks like it needs some work on the aperture mechanism.

pierre506
1-Jul-2014, 19:07
117630
The barrel is in a quite good condition.
It has the click aperture scale positioning.

Jim Graves
1-Jul-2014, 19:45
Just measured my Kodak 14" CE in Ilex No. 5 Universal shutter with calipers with glass removed ... very close to the measurements you got for your shuttered lens on all f-stops.

Kevin Crisp
1-Jul-2014, 20:00
Is it absolutely full open at maximum aperture, or does it get there sooner than lining up on the mark?

Jim Graves
1-Jul-2014, 22:56
Kevin ... if you're asking about the 14" CE in the Ilex No. 5 Universal ... my aperture measures at 52mm when set @ f-6.3 ... as does OP's ... but it opens to 57mm when moved beyond the f-6.3 setting to the end of it's range.

Interesting thing is ... if you divide 14" by 57mm you get 6.3 ?!?!?! But, of course, optics are not that simple ... with nodal points, etc., etc., etc. More thinking than I want to do ... I just put the pointer on 6.3, set the meter for 6.3, and forget about the caliper measurements. I'm just going to assume they knew what they were doing when they made the lens. As for OP's friend and his barrel lens ... I have no idea what happened.

goamules
2-Jul-2014, 05:36
Kevin ... if you're asking about the 14" CE in the Ilex No. 5 Universal ... my aperture measures at 52mm when set @ f-6.3 ... as does OP's ... but it opens to 57mm when moved beyond the f-6.3 setting to the end of it's range.

Interesting thing is ... if you divide 14" by 57mm you get 6.3 ?!?!?! But, of course, optics are not that simple ... with nodal points, etc., etc., etc. More thinking than I want to do ... I just put the pointer on 6.3, set the meter for 6.3, and forget about the caliper measurements. I'm just going to assume they knew what they were doing when they made the lens. As for OP's friend and his barrel lens ... I have no idea what happened.

Try this, measure with your calipers the iris opening with the glass on, then off. You will have different measurements.

Jim Graves
4-Jul-2014, 18:29
From the front or the back?

pierre506
4-Jul-2014, 23:34
I took off the rear groups to measure the actual size.

Jim Graves
5-Jul-2014, 00:53
Measured from front and back with the lenses in ... with the aperture set at f-6.3 ... measures out at 52mm on both ... exactly the same measurements as with the glass removed.

Am I missing something??

goamules
5-Jul-2014, 05:38
I suggest everyone read about the Entrance Pupil. "The entrance pupil is the image of the aperture stop formed by all optical elements anterior to the stop."

There is a good diagram here, Fig 67: http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v1/v1c030.html#ape

goamules
5-Jul-2014, 09:22
I made a post that may help http://www.largeformatphotography.info/forum/showthread.php?114769-Entrance-Pupil-and-how-to-properly-measure-Lens-Speed&p=1150706#post1150706