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Thread: CYZ 28-85 converted to Sony Alpha mount

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    CYZ 28-85 converted to Sony Alpha mount

    It's been a long trip but arent't they all when you're breaking new ground. All my attempts using an M42 adapter ended in failure when trying to focus to infinity. A new approach was needed and here it is.

    This conversion is pretty simple but you do have to disassemble and remove part of the aperture controls from the lens to the camera, grind down the lens housing at the rear and a locking divot must be drilled in the rear plate of the contact. The tough part will be making the flange.

    What we, my machinist and I, did was to create a set of blades that mount where the old contax blades mount. The mounting is easy but getting rid of all the conflicting protrusions took some time. At this point I have a working flange and making copies should be fairly easy in the future. Very little can be done on the lathe and most must be done on a mill or by hand.

    Here are some pics.














    Mike

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Wow. Nice work. So the question is, when are you going into the conversion business?

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Nicely done sir.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    It must have been a lot of fun. I used to have this lens in my old Contax collection. But apart from the fun of doing the conversion and sentimental attachment to good old gear, I don't see the interest in doing this as the Zeiss 24-70 is arguably the best lens in this range. It outperformed the Contax 35-70 and the 28/2.8 in my tests which in they turn outperform the 28-85.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Interesting. I found the 35-70 to be superior to any shots I could find from the 24-70 which is terrible in the corners at almost any usable aperture. Unfortunately I didn't have an opportunity to test one myself. Then there is the weight....

    Besides I'm on a budget.

    Mike

    Quote Originally Posted by edwardkaraa View Post
    It must have been a lot of fun. I used to have this lens in my old Contax collection. But apart from the fun of doing the conversion and sentimental attachment to good old gear, I don't see the interest in doing this as the Zeiss 24-70 is arguably the best lens in this range. It outperformed the Contax 35-70 and the 28/2.8 in my tests which in they turn outperform the 28-85.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by docmaas View Post
    Interesting. I found the 35-70 to be superior to any shots I could find from the 24-70 which is terrible in the corners at almost any usable aperture. Unfortunately I didn't have an opportunity to test one myself. Then there is the weight....

    Besides I'm on a budget.

    Mike
    Mike,

    In no way did I mean to undermine your efforts and this pioneer work is very interesting in that it opens the way to adapting really good Contax lenses that don't have an equivalent in the ZA line.

    When I first got the A900 and ZA lenses I still had a 1Ds2 and a full line of Contax lenses, and I did do many tests to check what I'm getting into. I found the 24-70 corners to be extremely sharp from f/5.6 and better than many lenses at f/4. I tested the 24-70 against the 28/2.8 and 35-70 at matching focal lengths, wide open and stopped down to f/5.6. I found the 24-70 to be equal to the 28 prime in the center and sharper in the corners. It was also marginally sharper than the 35-70 both in the center and corners, but I give the 24-70 the additional advantage because it was compared at 24.6mp while the 35-70 was used on a 16.7mp body.

    I certainly would disagree with you about the term "terrible". Corners certainly are not so good at f/2.8 but at f/5.6 they are excellent. 35mm is the sweet spot of the 24-70 while 50mm is the sweet spot of the 35-70. Both are at their weakest at 70mm but the 24-70 behaved much better at this FL.

    As for the 28-85, my copy suffered from severe zoom creep, which made it difficult to use for critical work on tripod. It is designed to be used wide open as the center sharpness is at its best wide open and corners are never really good until f/8-11. Even though it has more useable FL, I much preferred the 35-70 for the incredible sharpness at f/5.6.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    What we need to lobby for is Zeiss to extend the Z line to Sony mounts ... hopefully, with CPUs. Wouldn't mind a 21/2.8, 28/2, 35/2, or especially a 50/2 Macro availability.

    These conversons would be cool on some of the older super fast Zeiss primes ... like the 55/1.2 and 85/1.2 and maybe 100/2 ... that would be a nice match for the 135/1.8.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by fotografz View Post
    What we need to lobby for is Zeiss to extend the Z line to Sony mounts ... hopefully, with CPUs. Wouldn't mind a 21/2.8, 28/2, 35/2, or especially a 50/2 Macro availability.

    These conversons would be cool on some of the older super fast Zeiss primes ... like the 55/1.2 and 85/1.2 and maybe 100/2 ... that would be a nice match for the 135/1.8.
    +1

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by docmaas View Post
    It's been a long trip but arent't they all when you're breaking new ground. All my attempts using an M42 adapter ended in failure when trying to focus to infinity. A new approach was needed and here it is.

    This conversion is pretty simple but you do have to disassemble and remove part of the aperture controls from the lens to the camera, grind down the lens housing at the rear and a locking divot must be drilled in the rear plate of the contact. The tough part will be making the flange.

    What we, my machinist and I, did was to create a set of blades that mount where the old contax blades mount. The mounting is easy but getting rid of all the conflicting protrusions took some time. At this point I have a working flange and making copies should be fairly easy in the future. Very little can be done on the lathe and most must be done on a mill or by hand.
    Very nice! I hope we can soon get samples of pics ... please

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    Re: CYZ 28-85 converted to Sony Alpha mount

    I'd bet that Zeiss' ZA contract with Sony prevents them from adding the ZF-style lenses to the Sony lineup, but I hope I'm wrong. At least there a few useable ZS lenses.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by fotografz View Post
    What we need to lobby for is Zeiss to extend the Z line to Sony mounts ... hopefully, with CPUs. Wouldn't mind a 21/2.8, 28/2, 35/2, or especially a 50/2 Macro availability. (...)
    +2 ... autofocus of course

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by douglasf13 View Post
    I'd bet that Zeiss' ZA contract with Sony prevents them from adding the ZF-style lenses to the Sony lineup, but I hope I'm wrong. At least there a few useable ZS lenses.
    I tried to be a smarta** and asked Zeiss if they plan to release any of the MF lenses in Sony Alpha mount. Guess what? They completely ignored my email

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    Re: CYZ 28-85 converted to Sony Alpha mount

    Quote Originally Posted by fotografz View Post
    What we need to lobby for is Zeiss to extend the Z line to Sony mounts ... hopefully, with CPUs. Wouldn't mind a 21/2.8, 28/2, 35/2, or especially a 50/2 Macro availability.
    .
    Maybe the 100/2 makro, but I wouldn't want any of the other ones, because the 24-70 is simply better. Just go to slrgear and compare for instance the 24-70 at 24mm and the 28/2. The 24-70 outperforms it up to f/8 (too bad it was not tested at 28mm, but according to my own tests, it gets clearly better at 28 and keeps on improving up to its sweet spot at 35mm). Even at 2.8 the zoom is better. As for the 21/2.8 I would also want one, if it performs as good or better than the Contax 21 (and the 16-35). I have never tried the Contax version, but I can safely say that except for the extreme corners, the ZA zoom has plenty of sharpness to compete with them.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    FWIW, I emailed slrgear the other day and requested that they re-test the 24-70Z with the A900 as well, because their current results are only with the A700. They were very polite and said they'd get on it ASAP.

    On a side note, has anyone noticed any creaking in the zoom ring on their 24-70? I've had it since the camera arrived last March, and I finally got around to sending it in for repair two days before my warranty was up .lol.

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    Re: CYZ 28-85 converted to Sony Alpha mount

    No problem Edward. I did search for A900 shots with the 24-70 and my impression from the few I found was that the corners were quite weak. I didn't get one to try myself so that is as much as I can say. Hopefully someone like Mark Welch will put it through some rigorous comparison testing that will reveal just how good it is. I've seen a lot of enthusiasm for the lens and a little bit of disappointment as well. But sharpness out to the edges and into the corners is one of the things that really sets a good lens apart from a medicocre one and full frame corners are not one of the strong points of that lens from what I have seen and read.

    As I said though I'm on a budget and both the 28-85 and 35-70 are within my means while the 24-70 and 16-35 are not. Besides that I'm a lot more interested in a lens with a max aperture in the 3.5-4 range that is light and performs well at max aperture than I am one with a larger aperture that needs to be stopped down to get good sharpness. Why carry the weight of all that lowlight glass if you won't be happy with the results it gives you.

    I used to think I had to have f2.8 but I don't think that way any more. Now I think good quality and f4 or thereabouts is a better match for someone who wants to spend less and carry less weight. Leica, Zeiss and Minolta seem to make a lot of lenses for people who think like me. I'm finding though that Minolta glass is just a little bit below Zeiss in iq for me.

    My 35-70 I started this project with had been dropped and while it seemed to focus to infiinity at 70mm it didn't at 35. It does fine in medium distance shots though. Today I won a second one on ebay and I will be converting it as well. Then I'll decide between the two lenses.

    If the 24-70 really is an excellent lens there will be used ones available soon enough.

    Mike

    Quote Originally Posted by edwardkaraa View Post
    It must have been a lot of fun. I used to have this lens in my old Contax collection. But apart from the fun of doing the conversion and sentimental attachment to good old gear, I don't see the interest in doing this as the Zeiss 24-70 is arguably the best lens in this range. It outperformed the Contax 35-70 and the 28/2.8 in my tests which in they turn outperform the 28-85.
    Quote Originally Posted by edwardkaraa View Post
    Mike,

    In no way did I mean to undermine your efforts and this pioneer work is very interesting in that it opens the way to adapting really good Contax lenses that don't have an equivalent in the ZA line.

    When I first got the A900 and ZA lenses I still had a 1Ds2 and a full line of Contax lenses, and I did do many tests to check what I'm getting into. I found the 24-70 corners to be extremely sharp from f/5.6 and better than many lenses at f/4. I tested the 24-70 against the 28/2.8 and 35-70 at matching focal lengths, wide open and stopped down to f/5.6. I found the 24-70 to be equal to the 28 prime in the center and sharper in the corners. It was also marginally sharper than the 35-70 both in the center and corners, but I give the 24-70 the additional advantage because it was compared at 24.6mp while the 35-70 was used on a 16.7mp body.

    I certainly would disagree with you about the term "terrible". Corners certainly are not so good at f/2.8 but at f/5.6 they are excellent. 35mm is the sweet spot of the 24-70 while 50mm is the sweet spot of the 35-70. Both are at their weakest at 70mm but the 24-70 behaved much better at this FL.

    As for the 28-85, my copy suffered from severe zoom creep, which made it difficult to use for critical work on tripod. It is designed to be used wide open as the center sharpness is at its best wide open and corners are never really good until f/8-11. Even though it has more useable FL, I much preferred the 35-70 for the incredible sharpness at f/5.6.

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