Tamron Adaptall-2 question

[Chulster]

Can anyone here confirm whether Tamron's Adaptall-2 Nikon AI-S mount supports the key AI-S feature of accurate camera control of aperture?

Adaptall-2 mounts came in both AI and AI-S flavors. Will a lens with the AI-S version of the mount support accurate camera control of aperture assuming you use it on a camera that can control aperture, such as a Nikon FA?

The "accurate" part of the question is important, because even if the mount signals to the camera that it supports camera control of aperture, that support will be worthless if the stop-down lever of the mount does not have the linear movement required for accurate aperture control by the camera. If the stop-down lever behaves non-linearly like on an AI lens, exposures will not be accurate.

Anyone know the answer? I don't have any Adaptall-2 mounts myself; if I had an AI-S one, I could examine it and look for the telltale cam mechanism that AI-S lenses have (and AI ones don't).

Oh yeah, I almost forgot to mention. I realize that the question of AI-S vs AI is insignificant when using a DSLR, since no DSLR has the ability to distinguish between these lens types. However, it makes a difference when you plan to install a Dandelion CPU on the lens. If you install a CPU on an AI lens, controlling aperture through the camera will result in inaccurate exposures for the reason already mentioned. I do plan to install a chip on an Adaptall-2 AI-S lens—but only if it properly supports camera aperture control.

[Erik Lund]

Adaptall 2 mount converter seems to be AI and AI-s but need to be investigated if a Dandelion CPU can work,,,



    -3161-p.jpg]   [url=https://www.heritagecameras.co.uk/ekmps/shops/heritagecameras/images/tamron-adaptall-2-auto-lens-mount-for-nikon-ai-ais-many-af-and-digital-slrs-box-cap-[3]-3161-p.jpg]   [url=https://www.heritagecameras.co.uk/ekmps/shops/heritagecameras/images/tamron-adaptall-2-auto-lens-mount-for-nikon-ai-ais-many-af-and-digital-slrs-box-cap-[4]-3161-p.jpg]   [url=https://www.heritagecameras.co.uk/ekmps/shops/heritagecameras/images/tamron-adaptall-2-auto-lens-mount-for-nikon-ai-ais-many-af-and-digital-slrs-box-cap-[5]-3161-p.jpg]    Mount to fit Tamron Adaptall 2 and SP lenses onto Nikon AI manual focus SLR cameras, plus some AF and digital models with restrictions (see below)
 

• Tamron Adaptall 2 lens mount

• Fits Tamron Adaptall lenses

• For Tamron Adaptall 2 lenses

• For Tamron AD2 SP lenses

• For Nikon pre-AI manual SLRs

• For Nikon AI manual focus SLRs

• Fits some AF and digital SLRs

• Full aperture metering system

• ADR aperture direct readout

• Boxed with cap, instructions

Tamron has produced a wide range of Adaptall and Adaptall 2 lenses over many years, including not only the common wide angles, telephotos and zooms, but also some outstanding SP (Super Performance) types such as the 17mm f/3.5, 24-48mm f/3.5, 35-105mm f/2.8, 400mm f/4, 500mm f/8 mirror and many others. Using interchangeable mounts, these lenses can be fitted to most SLR cameras, classic and modern, and even many AF and digital models.
 
 This is a mount to fit Tamron Adaptall 2 and SP lenses onto Nikon pre-AI and AI manual focus 35mm film SLR cameras, plus some AF and digital models with manual focus and other restrictions (see below). It can also be used on the earlier Tamron Adaptall lenses, though the maximum aperture of the lens isn't transmitted to the camera. This doesn't matter on most film or any digital models - please contact us for more details. Focusing is manual, of course, but most AF and digital cameras will give electronic focus confirmation with lenses of f/5.6 or faster.
 
 Auto diaphragm and full-aperture metering on most AI cameras, compatible with all manual and auto exposure modes, including program where available. ADR (aperture direct readout) scale for cameras that display this in the viewfinder. Suitable for older (pre-AI) cameras, with auto diaphragm and stopped down metering where available. Also usable on many film and digital AF SLRs, with manual focus and other restrictions (see below). Works well on the Nikon D200, D300, D700, D7000, D1, D2 series, D3 and Fujifilm S5 Pro, in aperture priority auto and manual exposure modes.

[Chulster]

Which bits of that description are you adducing to conclude that this mount is Ai-only? Is it the italicized part?

I wish I could view the linked page to read the "other restrictions (see below)" alluded to in the quoted text, but the link doesn't work.

[Chulster]

Oh, I just noticed this promising bit in the last paragraph from that Heritage Cameras page (which I was able to view from a Google link):

Auto diaphragm and full-aperture metering on most AI cameras, compatible with all manual and auto exposure modes, including program where available.

The part that I italicized indicates to me the adapter does indeed support AI-S functionality, i.e., camera control of aperture. If it did not, Program AE mode would not work (or not work properly).

This is enough evidence to persuade me to take a chance on installing a Dandelion CPU on a Tamron SP 90mm f/2.5 with the AI-S adapter. Thanks for the link!

[Bent Hjarbo]

The linear responce must be at behavior of the lens not the mount. So if mounted on a len with an unlinear aperture responce it will give incorrect exposure.
O r did I miss something

[Chulster]

The linear responce must be a behavior of the lens not the mount. So if mounted on a lens with an unlinear aperture response it will give incorrect exposure.

I think this is probably correct, but it might go either way? Let's assume that Adaptall (v1) lenses don't have linear aperture movement (a safe assumption, probably). If Tamron's engineers were clever enough, they might have been able to convert the nonlinear movement of those stop-down levers to linear movement using a fancy mechanism in the Adaptall-2 adapter. 

On the other hand, your inference is more likely, and you will only get linear aperture movement if the lens itself has it.

Eagerly awaiting the eBay auction to end so i can (hopefully) buy that 90mm f/2.5 lens and give it a try!

[Thomas Stellwag]

I own the adapt all 500 mirror, but have never found out if the f 8 is linear or not 
using modern sensors and shooting raw, those differences of 1/3 to 1/2 stops should easily to be corrected

[Chulster]

Using modern sensors and shooting raw, those differences of 1/3 to 1/2 stops should easily be corrected

Good point. Unfortunately, the exposure error when using camera aperture control on an Ai lens can be up to 2 stops! This was determined experimentally by a fellow named Thomas Pindelski by using a Dandelion CPU on various Ai (non-S) lenses and using the camera to control the aperture.

That's why I'm so concerned that the Tamron Adaptall-2 AI-S mount actually work the way it's supposed to.

[Erik Lund]

The linear responce must be at behavior of the lens not the mount. So if mounted on a lens with an unlinear aperture responce it will give incorrect exposure.
O r did I miss something

This is a real important point, you can not have a universal adapter that takes all the different types of unlinear lenses into account, so they all need to be linear.

[Erik Lund]

Which bits of that description are you adducing to conclude that this mount is Ai-only? Is it the italicized part?

I wish I could view the linked page to read the "other restrictions (see below)" alluded to in the quoted text, but the link doesn't work.

Sorry I didn't read the article thoroughly, I agree it doesn't state AI lenses only, it just states it works with AI cameras, a very funny designation!  now that I did read it, I found the missing link and it seems like it is sort of almost linear for some of the lenses,,, Good luck, please provide a comprehensive test when you are done chipping 

 Here:
https://www.flickr.com/groups/69295920@N00/discuss/72157648778093276/
And here:
https://photo.stackexchange.com/questions/41165/how-does-the-dandelion-chip-affect-the-aperture-lever-with-old-lenses-on-nikon-d
Quote:
The Adaptall 2 mount lenses do have a linear aperture actuator, otherwise they couldn't be used in Program or shutter priority mode on cameras that offered the feature(s). And they certainly did work in "P" mode on the Minolta X700. (Except for the 500mm/8, obviously.) The most complicated part of the mount adapter was the lever mechanism that went between the camera's aperture lever and the lens's aperture actuator; on some long-flange-distance mounts, there wasn't a whole lot of room inside the adapter to correct the ratio, so it would require a multistage approach.

[Chulster]

Thanks, Eric! That information is exactly what I was looking for and confirms (to my satisfaction) that Adaptall-2 lenses (at least some of them) do have constant aperture movements. What isn't known, seemingly, is whether that linearity is a property of the lens or the mount—I think the lens is more likely, but it doesn't really matter either way.

I'm surprised I couldn't find these links in my own googling. I bow to your superior googling skills!

[Chulster]

I received the lens today. The Dandelion chip will be here Friday.

Having examined the aperture stop-down mechanism of the Adaptall-2 N/AI mount, I have serious doubts whether its movement is linear with respect to aperture area. When I move the stop-down lever slowly and evenly with my finger, the diameter of the aperture diaphragm changes in a linear fashion. This is in contrast to an AI-S lens, in which the area of the aperture changes linearly.

I'm 95% sure about this, but the true test will come when I install the Dandelion and try to use the camera to control aperture. I find myself actually a bit reluctant to do the necessary surgery on the mount to make room for the chip, because I believe that camera control of aperture won't work right with this lens. However, even if it doesn't, the Dandelion will still provide the other benefits, such as obviating the need to use Non-CPU Lens Data, so installing the chip won't do any harm and will do some good in any event.

Having the chip identify the lens will be great because, as I discovered tonight, the Non-CPU Lens Data feature doesn't allow you to enter a focal length of 90mm!

Anyway, I've had a little time to play around with the lens, and I must say, this lens is unreasonably sharp. It's possibly the sharpest lens I've ever used at f/2.8. I'm actually flummoxed that a $125 lens dating from the late 1970s or the 1980s could be this sharp. Also, its field is extremely flat, even at non-macro distances. Evaluation of other qualities, such as contrast and color, will have to wait.

I'll report again once I've installed the Dandelion, but I'm not hopeful about that.

[Hugh_3170]

The Tamron SP 90mm f/2.5 with the Adaptall mount had an excellent reputation back when it first came out.  My uncle had one that was his preferred lens for copy work.

[Roland Vink]

You would have to investigate how the adaptor links the camera stop-down lever in the camera to the lens aperture lever.

If it is a direct pass-through linkage, similar to the PK-13 and other Nikon extension tubes, then the adaptor will preserve the linear stop-down action of AI-S lenses.

I have a feeling that the stop-down lever of Tamron Adaptall lenses works in the opposite direction from Nikon lenses (I might be wrong here). If so, the adaptor would need some way of reversing the stop-down action, and that may or may not support AI-S functionality.

Also, the travel of the stop-down lever in F-mount lenses is relatively short. If the Adaptall lenses have longer travel, so the adaptor may need to scale the movement up or down to match, which could also affect performance of AI-S lenses.

Even if the adaptor does in theory support AI-S, the extra mechanical linkage between the camera and lens could make the aperture control less accurate.

Of course the only way to be certain is to install the Dandelion chip and see how it works.

The Dandelion is a G chip, so when installed you can only control the aperture from the camera, you can't use the manual aperture ring (correct me if I am wrong). Personally, I prefer using the aperture ring, so the Dandelion chip is not an option for me. I never use Programme or Shutter Priority with manual lenses, I always use Aperture Priority or very rarely Manual. This gives me control over the DoF and the overall look of the image so AI-S functionality is not important either, I'm happy to enter CPU data into the camera - you just need to remember to select the right setting when changing lenses

[Chulster]

The Dandelion is a G chip, so when installed you can only control the aperture from the camera, you can't use the manual aperture ring (correct me if I am wrong).

Hi Roland,

The Dandelion has a setting to enable using the aperture ring to control aperture—this is setting "60" as described on Thomas Pindelski's Dandelion page. Of course, one must also enable use of the aperture ring in the camera's settings.

The linkage between the stop-down lever in the lens mount and the lens proper is fairly simple. The stop-down lever is attached to a ring; and then there is a mechanism that converts the rotation of this ring to an up-down motion (along the axis of the lens). This piece that moves up and down mates with a mechanism in the lens itself that also moves up and down. Finally, this up-down movement is converted to opening and closing of the aperture diaphragm via invisible means (invisible without disassembling the lens).

I will try to take a couple of videos of this linkage if I have the time and the inclination.