graybeard

A two part question. 1. on third party lenses - can I be fairly certain that as a rule of thumb they are designed for T-mounts, and all that is necessary to mate lens to body is the proper T-mount, which will have screw threads matching the lens on one side and the various camera mounts on the other side? 2. On native lenses, ie Canon, Nikon, Pentax etc is it possible to mount unlike lens to body? ie Nikon to Canon, Pentax to Nikon etc. Would this be accomplished with a specific adapter? Thank you.

Leitz Loc: Solms

T-mount lenses will attach to nearly all SLR/DSLR cameras with the proper T adapter. Other third-party lenses are available with mounts specifically for certain cameras. Do a search for any brand such as Sigma, Tokina, Tamron, Rokinon, &c., they say which camera mounts are available.
Here is a link to a popular US dealer which carries adapters to mount various lenses to different cameras. Hope this helps answer your question.

http://www.bhphotovideo.com/c/buy/Lens-Adapters/ci/3420/N/4077634486

GoofyNewfie Loc: Kansas City

T-mount lenses are still made but the majority of third-party are not that type. T mounts are found in simple, manual focus mirror lenses and pre-set telephotos. With the more complex autofocus lenses we have today, lens mounts are not user interchangeable.

Adapters are made so you can mount "alien" brand lenses on your camera body, but with most of them, you will lose some functionality like autofocus, automatic aperture control and metering. The lens mount flange to focal plane distance differs between camera mfg's so some simple adapters won't even allow infinity focus.(putting a Nikon lens on a Canon body works but not the reverse) There are some that have a corrective optical element to compensate but I believe that changes the focal length, plus you are putting a possibly questionable piece of glass into the image making process. As always, some are made better than others.

Metabones Speedbooster makes adapters that actually increase the aperture by one stop and reduce the focal length to .7 of the original lens. ie: your full-frame 50mm f/2 lens now behaves like a 35mm f/1.4.

blackest Loc: Ireland

1) no not really, take a company like sigma for example they will have versions for a number of different camera systems including their own with mounts to suit each camera system. Tameron developed its adaptall system where they designed a number of dedicated mounts taking a common lens. So you could have one with the canon mount and if you had the pentax k or ka adapter you could switch mounts.

Mostly from a users point of view you want a lens with an aperture ring and manual focus.

Manual focus doesn't necessarily mean you focus unaided. For example on my k200d there is a hexagon on the display which is solid when focus is achieved it also has in-body stabilization where you select the focal length when you turn on the camera,(for zooms you choose a focal length you intend to shoot at).

2) Registration distance is key to a successful mounting. Each lens is designed to focus the light a set distance behind the lens, with a camera with a mirror, that is a fair distance away. Pentax and Nikon have very similar distances and canon is shorter. Which means canon tends to be able to accept an adapter which has a canon lens mount on the rear and has the body side of a pentax or nikon mount on the front and holds the lens at its designed registration distance.

There can still be problems where the rear of the lens (especially zooms) can protrude to far into the camera body and get in the way of the swing of the mirror. with movable rear elements this might occur at the wide end but not at the telephoto end. Best to examine a lens carefully to see if it is safe before fitting it to your camera.

Where the registration distance is similar between camera bodies it is impossible to have an adapter that is small enough to hold the lens at its designed registration distance. So an adapter with a corrective lens has to be used usually with a single lens element (your camera now wears glasses). By inserting this element into the light path you will tend to be degrading the iq of the lens , like cheap reading glasses they are unlikely to be perfect for this pairing.

You are probably aware of extension tubes which hold a lens a little further away from the camera body which increases the magnification of the lens which is good for close up focus but loses infinity focus. Like reading glasses, great for macro or near macro imaging but useless beyond that limited range.

Mirrorless camera's have a much shorter registration distance than camera's with a mirror box, this makes it easy to make a cheap glass less adapter for most SLR lenses. Unfortunately with the micro 4/3rds systems you have a 2x crop factor which complicates things say a 150mm - 250mm zoom behaves as a 300mm - 500mm zoom which is great for small things far away.

However your wide angle lens will generally be 28mm effectively 56mm which isn't wide angle any more. You could use a 18-55mm lens designed for a cropped sensor camera which gets you to an effective 36mm field of view but because they were designed for automatic use, there is no aperture ring which leaves you shooting wide open, giving a narrow depth of field which is generally not what you want when shooting a landscape (i guess you might focus stack to compensate).

On the other-hand you generally will have a 14-42mm lens designed for mirrorless that you got with the camera, with the drawback its generally f3.5 at the bright end wide open. Not so good for indoor shots without flash.

There is also the speed booster type adapter which is available. This will lower IQ to a degree, it essentially works like a light funnel concentrating the incoming light on to the area at the back of the camera where your sensor is instead of spilling light all over the back of the camera. It effectively doubles the light by a stop but also highlights the weaknesses of the lens especially at the edges. It does readjust the crop factor by multiplying the focal length by ~0.7 so a 50mm full frame lens acts like a 35mm and the 2x crop factor makes it 70mm effectively For telephoto 300mm f4 would be similar to 420mm f2.8 and while it may be bad at the edges birders might not find it too bad as they tend to have to crop anyway.

On the other hand without the speed booster your 300mm is behaving like a 600mm , so upping the iso might not degrade the iq as much as adding the speedbooster optical element.

M42 lenses tend to be adaptable to most mounts, fully manual and can be very good in practice. You do need to research the lens though, being old doesn't automatically mean good.

There is also a danger you might find you become a collector of old lenses more than a photographer.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

I was amused by the title here. At first I though you were talking about little green men.

agillot

yes and yes , a T mount will adapt a T mount lens to any brand using the right adapter for that body .i use a T mount long lens on a pentax film and a nikon d 70 and 300 . i also use some pentax lenses on the nikons using a adapter from fotodiox [ $ 45 ] .when you are using a T mount your camera body will work in manual mode only , and manual focus [ like in the old days ] you set the speed on the body , and the opening on the lens . the light meter on body may not work [ does not on nikon ] due because the lens does not communicate with body [ f stops ] .

blackest Loc: Ireland

Light Meter works on Pentax green button stops down the lens and calculates the exposure.

Leitz Loc: Solms

The Df meters work even on a bellows with no electrical or mechanical communication with the lens.

graybeard

Thanks for the info. This is what I was looking for. I was already suspicious about Sigma, as I saw pics of the lens bases looked fixed, rather than T-mount. So I will have to avoid them. As to #2, I think I will avoid most big name lenses (probable anyway because of cost) except M42 lenses, which is what my old lenses are, and I have used them on my Canon digital. So far I have acquired 3 old 400mm TP lenses (still in the mail) and I am anxious to try them out.

redhogbill Loc: antelope, calif

:thumbup:

Blurryeyed Loc: NC Mountains.

I think that a member already explained to you registration distances and the need to purchase adapters with lenses vs adapters without lenses. Here is some very helpful information, it is a listing of the flange registration distances for most camera bodies. If your body has a shorter registration distance than the lens you are considering then you can usually find a glassless adapter for it. Personally I would not consider the purchase of a lens that I would have to use another lens to work properly, I would simply find lenses that can be adapted to my camera with a simple spacing adapter. I shoot canon so I have a wide variety of such lenses to choose from, such as Nikon, Yashica, Pentax, Olympus, etc... but I can't use the old Canon lenses which is a shame.

I guess that I should also add that if you are shooting with a full frame camera a little more investigation is necessary, the mirrors on the full frame cameras are larger than on the crop cameras and may come into conflict with the back of the lens or its levers, I have a 35mm Pentax Takumar that was one of my favorite lenses on my crop frame Canon DSLR but that I can not use on my full frame canon because the mirror will contact the back of the lens possibly damaging the camera's mirror.

http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

blackest Loc: Ireland

Thanks for that list, I think :)
The cheapest lenses are the ones which never made it in to the digital age. now with this list I can find loads of obscure lens mounts that will adapt to my camera's
I already have pentax bayonet to micro 4/3 if I get m42 to pentax k I can use m42 on pentax and micro 4/3 (with the K to 4/3 adapter). So many more lenses i can trawl through ebay looking for :) so much more GAS ...

LFingar Loc: Claverack, NY

Yeah! I thought there would be some great photos from Area 51! I was kinda curious just where a lens on an alien body would be mounted. :lol:

graybeard

Pretty much the same idea I have. I am perplexed by the reactions of some people... ranging from dismissal to outright hostility. No doubt we may be bidding against each other on ebay, actually raising the prices when we want just the opposite !! Anyway, good luck and let us know about some of your experiences.

blackest Loc: Ireland

Possibly not shipping from the US is expensive, and will ensure a cheap lens attracts duty even if it was a 99 cent lens.