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pshute
Joined: 16 Oct 2009
Posts: 15
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 Posted: Sat Jul 31, 2010 4:39 pm Post subject: Sigma APO 400mm/f5.6 - what's this tab for? |
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pshute wrote:
I have the Contax/Yashica version of this lens. There's a little black tab protruding from the base of the lens, at about 7 o'clock, looking from the back of the camera.
It looks like it could be pressed in, perhaps to close the aperture for DOF preview, but it won't move. Does anyone know the purpose of this tab? Is it for aperture preview (and therefore jammed), or just something to do with the mount? |
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Screamin Scott
Joined: 13 Oct 2007
Posts: 1014
Location: Dallas, Georgia USA
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| Posted: Sat Jul 31, 2010 6:06 pm Post subject: |
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Screamin Scott wrote:
Post a photo of it...
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Cameras-Nikon D300, D7100,D610,FE2,FTN ,FT2,N90s, Olympus Pen EP-3 & Olympus OM-D E-M10
Nikkor AF Zooms=28-105/3.5D,28-70/3.5D,35-135/3.5, et al
Nikkor AF //50/1.8,//Nikkor MF//50/2ai,50/1.8ais 50/1.4ai,24/2.8ais,28/2.8ai,28/3.5ai,55microAis/2.8,105/2.5ai,200/4ai,300/4.5ai35-135/3.5Ais,et al
Kiron /Kino made lenses//70-210/4ai,28-105/3.2ai,30-80/3.5ai,Viv 28/2ai,35-85/2.8aiVivS1,105/2.8Ais Dine,24-48/3.8ai VivS1,50-150/3.8aiViv,28-85/2.8aiViv,100/2.8Nai Viv,70-210/3.5Nai Viv,28/2.5ai Viv Komine made Viv//24/2Ais,135/2.8aiCF,28-50/3.5ai,28-90/2.8ai Viv S1,80-200/4.5aiCosina made Viv 19/3.8 Ais...Also Sigma 24/2.8 Ais Tokina made24/2.8ai VivAF Sigma 21-35/3.5,& other lenses... A link to some of my Flickr albums...
https://www.flickr.com/photos/screaminscott/albums |
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pshute
Joined: 16 Oct 2009
Posts: 15
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| Posted: Sat Jul 31, 2010 11:31 pm Post subject: |
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pshute wrote:
| Screamin Scott wrote: |
| Post a photo of it... |
Here it is. The picture of the whole lens doesn't show the tab, that's just for identification. The red arrows show the location of the tab in the closeups. Excuse the imprecise focus, I can't control the AF on this little Ixus 80IS, it keeps picking a different part of the picture.
I notice there's a little bit cut away from the CY-4/3 adapter right where this tab travels while attaching the adapter, although it doesn't actually protrude into that area.
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Screamin Scott
Joined: 13 Oct 2007
Posts: 1014
Location: Dallas, Georgia USA
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| Posted: Sun Aug 01, 2010 1:56 am Post subject: |
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Screamin Scott wrote:
I'm stumped as to it's purpose....
_________________
Cameras-Nikon D300, D7100,D610,FE2,FTN ,FT2,N90s, Olympus Pen EP-3 & Olympus OM-D E-M10
Nikkor AF Zooms=28-105/3.5D,28-70/3.5D,35-135/3.5, et al
Nikkor AF //50/1.8,//Nikkor MF//50/2ai,50/1.8ais 50/1.4ai,24/2.8ais,28/2.8ai,28/3.5ai,55microAis/2.8,105/2.5ai,200/4ai,300/4.5ai35-135/3.5Ais,et al
Kiron /Kino made lenses//70-210/4ai,28-105/3.2ai,30-80/3.5ai,Viv 28/2ai,35-85/2.8aiVivS1,105/2.8Ais Dine,24-48/3.8ai VivS1,50-150/3.8aiViv,28-85/2.8aiViv,100/2.8Nai Viv,70-210/3.5Nai Viv,28/2.5ai Viv Komine made Viv//24/2Ais,135/2.8aiCF,28-50/3.5ai,28-90/2.8ai Viv S1,80-200/4.5aiCosina made Viv 19/3.8 Ais...Also Sigma 24/2.8 Ais Tokina made24/2.8ai VivAF Sigma 21-35/3.5,& other lenses... A link to some of my Flickr albums...
https://www.flickr.com/photos/screaminscott/albums |
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visualopsins
Joined: 05 Mar 2009
Posts: 10960
Location: California
Expire: 2025-04-11
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| Posted: Sun Aug 01, 2010 2:12 am Post subject: |
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visualopsins wrote:
Guessing the lever is for dof preview, but operates only when lens is mounted on camera.
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Cameras: Sony ILCE-7RM2, Spotmatics II, F, and ESII, Nikon P4
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M42 Carl Zeiss Jena Flektogon 2.4/35
Contax Carl Zeiss Vario-Sonnar T* 28-70mm F3.5-4.5
Pentax K-mount SMC PENTAX-A ZOOM 1:3.5 35~105mm, SMC PENTAX ZOOM 1:4 45~125mm
Nikon Micro-NIKKOR-P-C Auto 1:3.5 f=55mm, NIKKOR-P Auto 105mm f/2.5 Pre-AI (Sonnar), Micro-NIKKOR 105mm 1:4 AI, NIKKOR AI-S 35-135mm f/3,5-4,5
Tamron SP 17mm f/3.5 (51B), Tamron SP 17mm f/3.5 (151B), SP 500mm f/8 (55BB), SP 70-210mm f/3.5 (19AH)
Vivitar 100mm 1:2.8 MC 1:1 Macro Telephoto (Kiron)
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aoleg
Joined: 22 Feb 2008
Posts: 1387
Location: Berlin, DE
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| Posted: Sun Aug 01, 2010 7:00 am Post subject: |
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aoleg wrote:
That's the MM tab telling the camera the lens is Multi Mode (MM) compatible. All Contax MM lenses (smallest aperture in green) have it; Yashica ML and Contax AE lenses (smallest aperture in white) never had it.
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pshute
Joined: 16 Oct 2009
Posts: 15
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| Posted: Sun Aug 01, 2010 7:47 am Post subject: |
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pshute wrote:
| aoleg wrote: |
| That's the MM tab telling the camera the lens is Multi Mode (MM) compatible. All Contax MM lenses (smallest aperture in green) have it; Yashica ML and Contax AE lenses (smallest aperture in white) never had it. |
Thanks for that, I knew someone would know. I Googled it, and although I'm still not sure exactly what it does, I'm sure it isn't a preview tab. Is it ever supposed to move?
And, given that this lens is unlikely to ever be used on a Contax camera again, would it decrease the value of this (fungus affected) lens if I removed it to try to rig up a preview button? Not sure if that idea's practical, I'll probably just end up wishing I never touched it.
A preview button would be helpful. Bird photography and stopping down manually don't really mix well. |
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AhamB
Joined: 22 Jun 2008
Posts: 733
Location: Germany
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| Posted: Sun Aug 01, 2010 2:08 pm Post subject: |
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AhamB wrote:
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| Another technical distinction is that the MM lens has a tab at the lens mount to signal the camera body that it is an MM lens. The real distinction, though, is that the MM lens has a lighter weight diaphragm assembly which allows the camera body to set the f stop for program or shutter preferred modes. The multimode camera body will provide program or shutter preferred operation only with an MM lens. |
From: http://www.mir.com.my/rb/photography/htmls/contax_history/history5.htm
The MM tab is absolutely fixed on my Contax Distagon 28/2.8. It has no function other than to signal the body that P and Tv mode are available and that it may set the aperture.
If you want to make an A/M switch or DoF preview button, you need a lever that pushes the long aperture lever (the one that doesn't move when you change the aperture). If you push that lever clockwise, the aperture opens. Maybe there are more ingenious ways of engaging and disengaging the aperture, but then you need do some hack to the aperture mechanism from the inside.
Last edited by AhamB on Mon Aug 02, 2010 7:01 am; edited 2 times in total |
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aoleg
Joined: 22 Feb 2008
Posts: 1387
Location: Berlin, DE
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| Posted: Mon Aug 02, 2010 6:39 am Post subject: |
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aoleg wrote:
| pshute wrote: |
| Is it ever supposed to move? |
Nope, its sole purpose is to trigger a pin on the camera that would signal that the lens mounted is MM compatible.
| pshute wrote: |
| And, given that this lens is unlikely to ever be used on a Contax camera again, would it decrease the value of this (fungus affected) lens if I removed it to try to rig up a preview button? Not sure if that idea's practical, I'll probably just end up wishing I never touched it. |
The lens will lose 10% of its value  Whether the few bucks are worth it for you is up to you. However, I don't believe it is possible with reasonable efforts to add a DoF preview lever to this lens.
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alex
Joined: 18 Apr 2009
Posts: 561
Location: UK
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| Posted: Mon Aug 02, 2010 7:40 am Post subject: |
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alex wrote:
aoleg is right, it's the MM tab, which tells compatible Contax bodies that a Multi-Mode lens is mounted, and that it can use Program and Shutter Priority modes, as well as Aperture priority mode. The tab doesn't move, it engages on a corresponding lug on the camera mount, and moves it slightly when the lens is mounted. It will mount successfully on a non-MM body, such as the Yashica CY SLRs.
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