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12-25-2015, 10:55 PM   #1
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Question about manual lens

On a couple manual lenses I've seen online it shows the f-stops twice on the lens (like in the photo).
My question is why are the F-stops on there twice?

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12-25-2015, 11:50 PM   #2
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This is an interchangeable mount lens. Most lenses have a aperture ring that moves the white number way. Minolta lenses go the opposite direction. If you have a Minolta camera, the lens mount installs in a way that only lets the aperture work on the green side.I believe this is a Vivitar TX mount lens
12-26-2015, 01:28 AM   #3
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Ah, ok. Thanks for the info!
12-26-2015, 04:16 AM   #4
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I have a cosinon 55/2.8 in m42 with two scales (which I haven't tried yet), one marked "auto" the other "manual". They work exactly like an auto/manual diaphram stop down switch, only less conveniently.

12-26-2015, 05:45 AM   #5
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QuoteOriginally posted by pentaxus Quote
If you have a Minolta camera, the lens mount installs in a way that only lets the aperture work on the green side.I believe this is a Vivitar TX mount lens
+1 - lens pictured is probably the earlier but similar T4 mount. If you can't see TX printed on the lens mount interior plate, it's T4.
Some mounts eg M42 the lens stops down either way. So if you blindly click all the way to (either) end you'll be at f16, not wide open!

http://www.tremyfoel.co.uk/photography/TX-UserManual.pdf

http://www.suaudeau.eu/memo/Manuels/Soligor_T4.pdf

Last edited by marcusBMG; 12-26-2015 at 05:51 AM.
12-26-2015, 12:18 PM   #6
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Two aperture rings could also mean a "preset lens''. Pentax had a few of them, recent ones include the shift lenses. These are manual diaphragm lenses.

Phil.
12-26-2015, 01:31 PM   #7
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QuoteOriginally posted by gofour3 Quote
Two aperture rings could also mean a "preset lens''. Pentax had a few of them, recent ones include the shift lenses. These are manual diaphragm lenses.

Phil.
I think his, like mine, has one ring with two scales, whereas my jupiter 9 is a preset with separate aperture and stop-down rings.
12-26-2015, 05:50 PM   #8
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Pentaxus has the correct answer. The whole idea of the TX mount was to supply full automation for the respective mounts and do-away with manual stop-down/preset operation of some of the earlier mount adapter systems.

To quote the Vivitar Owner's Manual for TX Wide Angle Lenses:
QuoteQuote:
The Aperture Ring (8) controls the amount of light allowed to reach the film by adjusting the size of the lens diaphragm opening. The higher the f-stop number, the smaller the diaphragm opening and the smaller the amount of light allowed to reach the film.
Vivitar Automatic TX Lenses and TX Lens Mount Adapters provide full coupling to the automatic diaphragm operation and through-the-lens metering system of your camera, even with "open aperture" and automatic exposure cameras. The automatic diaphragm operation of your TX Lens and Adapter combination allows you to focus and compose the picture with the diaphragm at maximum aperture, or "wide open," when the viewfinder image is brightest and easiest to see. When shooting, the diaphragm will automatically "stop down" to the pre-selected aperture at the moment of exposure and re-open immediately after exposure is made. NOTE: Two Aperture Scales are engraved on the Aperture Ring (8) of your TX Lens to assure proper coupling between TX Lens Mount Adapters and the cameras they are designed to fit. Refer to the TX Lens Mount Adapter instructions for the proper aperture scale to use with your TX Lens Adapter combination. (See Photo "G") (emphasis mine)
http://www.boggys.co.uk/download.php?filename=Vivitar_TX_Wide_Angle_Lenses_OM_400dpi.pdf

The parts list for TX lenses and adapters includes the instructions for each adapter. For Pentax K it reads:
QuoteQuote:
Note: When mounted correctly, the lens will function on the white aperture scale of the lens.
For Minolta:
QuoteQuote:
Note: When mounted correctly, the lens will function on the green aperture scale of the lens.
http://www.boggys.co.uk/download.php?filename=Vivitar_Tx_Lens_System_PL_400dpi.pdf


Last edited by Not a Number; 12-26-2015 at 06:15 PM.
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