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Author Topic: 24/25mm for Contax 645 & other MF cameras.  (Read 8546 times)

chiek

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Re: Pentax 645 25mm lens quality & compatibility with other MF cameras.
« Reply #20 on: December 09, 2015, 04:34:59 am »

You still haven't understand the conversion Chiek.... I don't modify the camera... I modify the lens as to work on the camera! This (for the Contax 645 body) can only be done with the Pentax 25mm (by making an adapter of 6.87mm thickness), or with the Samyang 24mm f3.5 T-S where one has to remove the rear part of the lens and fit a Contax C645 mount on it, that will be 19mm recessed on the lens so that the lens can then focus to infinity.


Sorry for my english but I think You don't understand what I mean. Why custom MOD lens?
I understood your think. but pls check attached picture,
In my opinion, price, Residual value, other… Canon+custom camera is better than your think.
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chiek imaging, in Seoul, SOUTH-KOREA.
Sinar P2, Hasselblad CFv-50c medium format and a7R systems
major job is products shot, especially for electronic products.
but interested in Landscapes and Portraits, Still-life.
my hobby is Designing camera…
www.chiek.co.kr

Theodoros

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Re: Pentax 645 25mm lens quality & compatibility with other MF cameras.
« Reply #21 on: December 09, 2015, 12:31:01 pm »

Sorry for my english but I think You don't understand what I mean. Why custom MOD lens?
I understood your think. but pls check attached picture,
In my opinion, price, Residual value, other… Canon+custom camera is better than your think.

But Chiek... the lens is needed because Contax can't go wider than 35mm... it's not needed to use a different platform with the MFDBs I have... for that, I am converting a Rollei x-Act2 which will end up having full interface communication with Contax lenses and backs and will have focal plane shutter too...

By the way... to modify the Samyang, it doesn't involve any cutting of the lens body at all... One needs to just unscrew the rear part of the lens (it is bolted) and then make an (dummy) adapter that will shorten the lens by 19mm and screw it back... 

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landscapephoto

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #22 on: December 09, 2015, 01:51:36 pm »

What is the image circle size of the Canon and Samyang 24mm lenses?
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #23 on: December 09, 2015, 02:42:32 pm »

What is the image circle size of the Canon and Samyang 24mm lenses?
Don't know about the Canon (didn't check as it is impossible to modify), but the Samyang is a huge 74mm... the respective Nikon 24mm PC-E (which - like the Canon - has electronic aperture control, so that it is impossible to modify) has 69mm.... All Canon 24mm TS-E, Nikon 24mm PC-E & Samyang 24mm T-S can cover a FF MFDB sensor....
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araucaria

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #24 on: December 09, 2015, 02:51:26 pm »

The samyang has horrible distortion.
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #25 on: December 09, 2015, 03:49:18 pm »

The samyang has horrible distortion.

That would be interested to know... do you have any references to back it up?
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landscapephoto

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #26 on: December 09, 2015, 04:40:36 pm »

Don't know about the Canon (didn't check as it is impossible to modify), but the Samyang is a huge 74mm... the respective Nikon 24mm PC-E (which - like the Canon - has electronic aperture control, so that it is impossible to modify) has 69mm.... All Canon 24mm TS-E, Nikon 24mm PC-E & Samyang 24mm T-S can cover a FF MFDB sensor....

The diagonal of the largest MF sensors is about 67mm, so you will not be able to shift with these lenses.
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #27 on: December 10, 2015, 11:37:59 am »

The diagonal of the largest MF sensors is about 67mm, so you will not be able to shift with these lenses.
I'm sure you posted without reading what the subject has turned out to be... What shifting are you talking about? ...the shifting mechanism will be removed off the lens and replaced with an self made simple construction which will shorten the lens by 19mm and turn it to Contax 645 mount...  The modification is fairly easy to do as the rear part of the lens is bolted on (it can be removed by unscrewing 4 screws) and the new rear part one can make by either shaving a Contax extension ring or by using a Hasselblad V to C645 lens adapter and shave the adapter a few milimeters from the Hassy side as to shorten the lens to the right size as to be adapted on a Contax...

The rear element is recessed enough into the Samyang 24mm T-S lens as not to interfere with the mirror of the camera body and the aperture ring is purely mechanical and is positioned (thank Lord) in the middle of the lens... Its purely a research I've done as I need to go wider than 35mm on the Contax and there is no dedicated lens to do that... Other than using the lens on the Contax, the lens can also be modified for M645 mount and for Leica S mount, thus providing a cheap alternative to the custom lenses made for these cameras.

Note that the lens is going to be used with a 37x49mm sensor, thus providing an 18mm 35mm format equivalent horizontally and a 16mm respective equivalent if the camera is used in portrait mode.
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landscapephoto

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #28 on: December 10, 2015, 01:26:02 pm »

That seems an extremely complicated solution. If you are not going to shift and only need a 37x49mm sensor, what about getting a second hand H3D or H4D and the HCD 24mm lens?
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #29 on: December 10, 2015, 04:13:11 pm »

That seems an extremely complicated solution. If you are not going to shift and only need a 37x49mm sensor, what about getting a second hand H3D or H4D and the HCD 24mm lens?

What you mean? Change Contax for Hasselblad? No thanks for the following reasons:
1. I'll loose the lens speed of my 45, 80 & 140 lenses...
2. I'll miss the built quality of the C645 lenses
3. The standard zoom (the 50-110) of Hasselblad is a PINA to use in comparison to the Contax 45-90...
4. The 50 to 80mm lens gap of Hasselblad is to much of a gap....
5. I use other equipment if the case requires high sync speed...
6. I'll loose the (perfect) ergonomics of the Contax body....
7. Changing platform is of considerable cost for gaining nothing....
8. My other back next to my Blad CF-39MS is a Sinarback 54H which is my most providing tool (Art repro is what I specialize with among my pro projects) can't be fitted on a Hasselblad H as there is no adapting plate for H cameras available for it.
9. My other system (for use with movements and leaf shutter cases) is Fuji GX-680 which has permanently on it an adapter plate so that one can use C645 backs on it...  There is no adapter plate as to use H backs of it.... (there was one, but proved problematic and it was stopped).
10. My Contax line of lenses (all but the 350) I also use on my Nikons with full dedication (of AF too) as I have the JAS adapter... I can't share Blad H lenses on my Nikons... 

 ;D
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landscapephoto

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #30 on: December 10, 2015, 05:18:52 pm »

What you mean? Change Contax for Hasselblad? No thanks for the following reasons:
1. I'll loose the lens speed of my 45, 80 & 140 lenses...
2. I'll miss the built quality of the C645 lenses
3. The standard zoom (the 50-110) of Hasselblad is a PINA to use in comparison to the Contax 45-90...
4. The 50 to 80mm lens gap of Hasselblad is to much of a gap....
5. I use other equipment if the case requires high sync speed...
6. I'll loose the (perfect) ergonomics of the Contax body....
7. Changing platform is of considerable cost for gaining nothing....
8. My other back next to my Blad CF-39MS is a Sinarback 54H which is my most providing tool (Art repro is what I specialize with among my pro projects) can't be fitted on a Hasselblad H as there is no adapting plate for H cameras available for it.
9. My other system (for use with movements and leaf shutter cases) is Fuji GX-680 which has permanently on it an adapter plate so that one can use C645 backs on it...  There is no adapter plate as to use H backs of it.... (there was one, but proved problematic and it was stopped).
10. My Contax line of lenses (all but the 350) I also use on my Nikons with full dedication (of AF too) as I have the JAS adapter... I can't share Blad H lenses on my Nikons... 

 ;D

As usual you are able to find 10 problems for any solution.
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #31 on: December 10, 2015, 05:34:08 pm »

As usual you are able to find 10 problems for any solution.

I think you mean "As usual one can find 10 problems for any solution."... yep! ...that's true!  ;D  That's why most pros take it step by step, stick with (carefully selected) equipment for a long time and only upgrade parts of it as to improve on the provision of it yet, without affecting negatively the tasks it can serve... In my case (this time), I need an UWA for my MFDBs.... changing platform affects negatively the tasks that my equipment  can be used on...
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Sam C

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #32 on: December 11, 2015, 11:46:18 pm »

As a fellow Contax 645 nutjob enthusiast, I'm anxious to see how it goes.  For now I use a Cambo technical camera when I need to go wider than the 35mm Contax (~21mm equivalent in "small format"  ::) ), using the same exact digital backs that I use on the Contax, but it would be great to use high quality glass on my Contax--I'm deeply in love with the Contax 645.
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #33 on: December 13, 2015, 11:47:25 am »

As a fellow Contax 645 nutjob enthusiast, I'm anxious to see how it goes.  For now I use a Cambo technical camera when I need to go wider than the 35mm Contax (~21mm equivalent in "small format"  ::) ), using the same exact digital backs that I use on the Contax, but it would be great to use high quality glass on my Contax--I'm deeply in love with the Contax 645.

The whole process, along with my other project that has been explained in an other thread and is about converting a Rollei X-act2 camera as to work with MFDBs and FF mirrorless, with full interface communication (and exif data) between lenses camera and backs (or mirrorless), will be posted here explaining the process (with pictures) step by step... Videos (for both projects) are planned to be uploaded on You Tube & Vimeo...
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chrismuc

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #34 on: December 15, 2015, 09:32:44 am »

Theo, how do you know that the Samyang has 74mm image circle? Total image circle or sharp image circle?
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #35 on: December 15, 2015, 03:25:36 pm »

Theo, how do you know that the Samyang has 74mm image circle? Total image circle or sharp image circle?

I know that the Nikon has 69mm image circle (my friend who owns one, tested it with me being present on his P3 with film) and the Nikkor vignettes at extreme shifts where the Samyang doesn't (according to tests) even at full shifts... so the difference is at least of 5mm (there is a good possibility that it is even more)... The measure of the Nikkor was done with focus at infinity...

Never the less, one must bear in mind that image circle (on all lenses) is measured with focus at infinity... This means that if a lens is used on a view camera and is focused to its closest possible focusing distance, the image circle will expand considerably. The same happens with zoom lenses that are expanding their image circle considerably as they are zoomed towards their long end... Now, coming back to your question about image having sharp image circle, the Samyang is reported to deliver sharp images at f5.6 to f11 across the frame with 10mm shifts on a FF sensor, so one should expect if the lens is not shifted, the image circle to be (at least) as sharp on a 37 x 49mm sensor which is only 6mm either side and surely much less than 10mm suggests... 10mm (on a FF sensor) would even cover well the furthest corners of a 37x49mm sensor....

Now, because the lens rear element is recessed considerably, It looks like the image circle at the the lens mount plane is wider than the mount's diameter (on an non converted lens).... This means that there is some influence on the lens performance (more evident at the edges of the frame) because the mount "obstructs" the full image circle to be projected... So if the lens is converted as to be mounted on an MF camera, one should expect even better performance at the edges of the frame than the 10mm shift on a FF sensor suggests, since there will be no obstruction from the rear mount of the lens as to obstruct the full image circle to be projected.
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araucaria

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #36 on: December 16, 2015, 01:25:13 pm »

That would be interested to know... do you have any references to back it up?
It's what the reviews said when it came out, I was totally going to buy one until I read these.
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #37 on: December 16, 2015, 01:31:03 pm »

It's what the reviews said when it came out, I was totally going to buy one until I read these.
Provide a link to the review then....
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alan_b

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #38 on: December 16, 2015, 03:31:14 pm »

Some info here, teardown on page 2:
http://www.lensrentals.com/blog/2013/05/first-look-at-the-rokibowyang-24mm-f3-5-tilt-shift-lens-part-1

More distortion & sharpness falloff than Canon/Nikon
« Last Edit: December 16, 2015, 03:34:25 pm by alan_b »
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Theodoros

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Re: 24/25mm for Contax 645 & other MF cameras.
« Reply #39 on: December 16, 2015, 03:54:49 pm »

Some info here, teardown on page 2:
http://www.lensrentals.com/blog/2013/05/first-look-at-the-rokibowyang-24mm-f3-5-tilt-shift-lens-part-1

More distortion & sharpness falloff than Canon/Nikon
Alan, thank you so much for this link.... much appreciated, In the second page one can clearly see that the conversion is much easier than I thought it will be! I will remove both the shift and the tilt mechanism! Fantastic pictures of the lens taken apart! One can clearly see how the lens is constructed! http://www.lensrentals.com/blog/2013/05/first-look-rokinon-24mm-f3-5-tilt-shift-part-2
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