Image Circle of Contax 645 Lens

[kimyeesan]

I am very interested in the Alpa upcoming Contax Shift mount for 12FPS. Would like to know how big the IC for Contax 45-90 and also 35mm. Does anyone has any experince or specification of these 645 lens? I am going to pair the lens with 44x33 CMOS sensor back.

In regards to IQ, how does the 45-90mm and 35mm perform at the corner? Thanks in advance.

 

[chrismuc]

Alpa was so nice to borrow me their Contax 645 version of the mount for the FPS which allows 12mm shift movements in all directions (left/right and up/down independingly and simultanously) and I did tests with some lenses (all with IQ180). The Contax 645 shift adapter is technically not yet the mass production version but the preliminary version they showed at Photokina 2014. Of course it has the latest firmware to control the aperture (and focus if required by the user!) of the Contax 645 lenses.

I did initial tests of several Contax 645 lenses from 35 mm to 210 mm but here to mention only the wide angle Distagons 35f3.5 and 55f3.5. Sorry Kim I don't own (any longer) the 45-90. All Contax 645 lenses work perfectly with the FPS, the camera recognizes the lens with its correct maximum aperture, the aperture can be choosen in the FPS menu (just like with Canon lenses using the FPS Canon EF mount), the aperture ring at the lens is out of function.

For my first tests I used f11 for all shots and auto-stitched in Photoshop CS6 always four pictures in landscape orientation after opening them in ACR and doing some basic adjustments (use equal color temperature, add some clarity, unsharp mask 100% 0,5 pixel, automatic reduction of chromatic aberation):*
- left 12mm
- left 12mm + up 12mm
- right 12mm + up 12mm
- right 12mm
This results in images 76mm wide and 52,5mm high (stiched sensor size) with about 150 MP resolution.

I added rulers to the images to better determine the sharp image circles and the total image circles.

Following links to the stiched files:

Contax 645 35f3.5

https://dl.dropboxusercontent.com/u.../Contax-645_35f3.5@f11_l12_u12-r12+rulers.jpg

total image circle: about 81 mm
sharp image circle: about 78 mm

I added a version of the same file reduced to IQ250 sensor size plus 12mm shift to all directions.

https://dl.dropboxusercontent.com/u...r/Contax-645_35f3.5@f11_l12_u12-r12-IQ250.jpg

As you can see, the image is perfectly sharp within +/- 12mm right/left OR up/down, just both together leaves the corners outside the total image circle.

Enclosed a second test image by the Contax 645 35f3.5.

https://dl.dropboxusercontent.com/u...pter/Contax-645_35f3.5@f16_u12-r12+rulers.jpg

This time at f16 and camera and sensor in portrait orientation, four pictures stiched together (center, 12 mm right, 12 mm right + 12 mm up, 12 mm up). Here I removed/reduced the geometrcial distortion of the single images first using the Alpa lens corrector plug-in for Photoshop before stiching them together. That works pretty well as one can see. At f16, the usable sharp image circle enlarges to about 80 mm (but of course the general sharpness is reduced slightly due to diffraction).

(Comment: The pre-series Alpa Contax 645 shift adapter is completely anodized in black but lacks inside matt coating. This leads to internal reflexions/flare which reduces the contrast especially of the super-wide angle 35 mm lens and even reflected stripe patterns can be seen in the sky in the left upper corner of the image. The series version of course will have the deeply black matt coatings which are standard for Alpa products.)

Contax 645 55f3.5

https://dl.dropboxusercontent.com/u.../Contax-645_55f3.5@f11_l12_u12-r12+rulers.jpg

total image circle: about 93 mm
sharp image circle: about 76 mm

The total image circle of the 55 is much larger than the 35, but the sharp image circle is slightly smaller. Also very useful with the Contax 645 shift adapter for the FPS.

The shift adapter works excellent. Alpa plans to release it (and the Hasselblad H and Rollei Hy6 versions) within the next months.

Christoph

 

[kimyeesan]

Thank you so much, Chris, for such a comprehensive test!!!!
How do you find the image quality? Does it compare well against Rodenstock HR lens on the Credo 50/IQ250 back?

 

[kimyeesan]

Another question, Chris, is where do you find the Lens Correction Profile for the digital back and Contax lens?

 

[kimyeesan]

Alpa was so nice to borrow me their Contax 645 version of the mount for the FPS which allows 12mm shift movements in all directions (left/right and up/down independingly and simultanously) and I did tests with some lenses (all with IQ180). The Contax 645 shift adapter is technically not yet the mass production version but the preliminary version they showed at Photokina 2014. Of course it has the latest firmware to control the aperture (and focus if required by the user!) of the Contax 645 lenses.

I did initial tests of several Contax 645 lenses from 35 mm to 210 mm but here to mention only the wide angle Distagons 35f3.5 and 55f3.5. Sorry Kim I don't own (any longer) the 45-90. All Contax 645 lenses work perfectly with the FPS, the camera recognizes the lens with its correct maximum aperture, the aperture can be choosen in the FPS menu (just like with Canon lenses using the FPS Canon EF mount), the aperture ring at the lens is out of function.

For my first tests I used f11 for all shots and auto-stitched in Photoshop CS6 always four pictures in landscape orientation after opening them in ACR and doing some basic adjustments (use equal color temperature, add some clarity, unsharp mask 100% 0,5 pixel, automatic reduction of chromatic aberation):*
- left 12mm
- left 12mm + up 12mm
- right 12mm + up 12mm
- right 12mm
This results in images 76mm wide and 52,5mm high (stiched sensor size) with about 150 MP resolution.

I added rulers to the images to better determine the sharp image circles and the total image circles.

Following links to the stiched files:

Contax 645 35f3.5

https://dl.dropboxusercontent.com/u.../Contax-645_35f3.5@f11_l12_u12-r12+rulers.jpg

total image circle: about 81 mm
sharp image circle: about 78 mm

I added a version of the same file reduced to IQ250 sensor size plus 12mm shift to all directions.

https://dl.dropboxusercontent.com/u...r/Contax-645_35f3.5@f11_l12_u12-r12-IQ250.jpg

As you can see, the image is perfectly sharp within +/- 12mm right/left OR up/down, just both together leaves the corners outside the total image circle.

Enclosed a second test image by the Contax 645 35f3.5.

https://dl.dropboxusercontent.com/u...pter/Contax-645_35f3.5@f16_u12-r12+rulers.jpg

This time at f16 and camera and sensor in portrait orientation, four pictures stiched together (center, 12 mm right, 12 mm right + 12 mm up, 12 mm up). Here I removed/reduced the geometrcial distortion of the single images first using the Alpa lens corrector plug-in for Photoshop before stiching them together. That works pretty well as one can see. At f16, the usable sharp image circle enlarges to about 80 mm (but of course the general sharpness is reduced slightly due to diffraction).

(Comment: The pre-series Alpa Contax 645 shift adapter is completely anodized in black but lacks inside matt coating. This leads to internal reflexions/flare which reduces the contrast especially of the super-wide angle 35 mm lens and even reflected stripe patterns can be seen in the sky in the left upper corner of the image. The series version of course will have the deeply black matt coatings which are standard for Alpa products.)

Contax 645 55f3.5

https://dl.dropboxusercontent.com/u.../Contax-645_55f3.5@f11_l12_u12-r12+rulers.jpg

total image circle: about 93 mm
sharp image circle: about 76 mm

The total image circle of the 55 is much larger than the 35, but the sharp image circle is slightly smaller. Also very useful with the Contax 645 shift adapter for the FPS.

The shift adapter works excellent. Alpa plans to release it (and the Hasselblad H and Rollei Hy6 versions) within the next months.

Christoph

Thanks!!! Where can I find the Lens Corrector Profile for Conax Lens?

 

[rupho]

You can download the free photoshop plug in from the Alpa website or use capture one 8 which apparently is using the Alpa lens corrector for the contax lenses. Works like a charm

 

[chrismuc]

Hi Kim,

I use the FPS only with Canon TSE, Contax 645, Hasselblad V and other MF lenses, but I don't use Rodenstock HR lenses. Also I don't have any experience with the IQ250 sensor but the pixel size of the 250 (5.3 um) is quite the same same like the 180/280 (5.2 um), so regarding sharpness requirement they are very similar.

The Alpa lens corrector plugin for Photoshop can be downloaded here:

ALPA of Switzerland - Manufacturers of remarkable cameras - ALPA Lens Corrector

Btw, the current version of C1 (8 I assume) also can correct the distortions (with and without shift) of Contax 645 (and many other lenses), the correction parameters come with the software (no plugin required).

 

[chrismuc]

Hi Grischa, thx, I was too slow writing

 

[kimyeesan]

Thank you so much for such detail insight into this setup. I am pretty convinced with the IQ.

 

[kimyeesan]

Chris, are you based in Guangzhou?

 

[joelorbita]

Image Circle of Hasselblad H Lenses on Alpa FPS and shift adapter?

I recently saw the Alpa Shift adapter for Hasselblad H lenses

ALPA of Switzerland - Manufacturers of remarkable cameras - Photokina 2014


and was wondering if anybody had information on the image circle of these lenses?

They obviously have a much larger image circle than 645 otherwise a "shift" adapter would be pointless..

I noticed a similar post by "kimyeesan" and see that "chrismuc" has had access to a preproduction version of the Contax 645 shift adapter and these results look very impressive!!


The one difference that I am wondering between these two camera systems (presuming that both have suitable image circles to be used with the shift adapter), is whether the Hasselblad H lenses will flash sync at their maximum sync speed on the Alpa FPS (using the lenses leaf shutters), even when using full shift on the Alpa adapter?

If so, that would be very cool indeed


Thanks so much, if anybody has any information, would be greatly appreciated!

 

[narikin]

As an ex-Contax 645 user, and current Alpa system (inc FPS) user, I have to caution your enthusiasm on this path, in that the old film lenses, mostly designed in the 1980's, or 90's at best, are simply not up to modern MF digital needs. They can give an 'interesting' look, and maybe a few of them, a very few mind you, are acceptable in their sharpness, but none will be able to resolve what a current generation Rodenstock Tech lens is capable of.

What they can do is provide a faster aperture, and affordability, (remember to factor in this pricey adapter!) but don't expect results that compare to a dedicated modern tech lens in resolution.

 

[kimyeesan]

As an ex-Contax 645 user, and current Alpa system (inc FPS) user, I have to caution your enthusiasm on this path, in that the old film lenses, mostly designed in the 1980's, or 90's at best, are simply not up to modern MF digital needs. They can give an 'interesting' look, and maybe a few of them, a very few mind you, are acceptable in their sharpness, but none will be able to resolve what a current generation Rodenstock Tech lens is capable of.

What they can do is provide a faster aperture, and affordability, (remember to factor in this pricey adapter!) but don't expect results that compare to a dedicated modern tech lens in resolution.

I understood that. It's the opportunity to use zoom lens, therefore more versatile that draw me to this path.

 

[kimyeesan]

As an ex-Contax 645 user, and current Alpa system (inc FPS) user, I have to caution your enthusiasm on this path, in that the old film lenses, mostly designed in the 1980's, or 90's at best, are simply not up to modern MF digital needs. They can give an 'interesting' look, and maybe a few of them, a very few mind you, are acceptable in their sharpness, but none will be able to resolve what a current generation Rodenstock Tech lens is capable of.

What they can do is provide a faster aperture, and affordability, (remember to factor in this pricey adapter!) but don't expect results that compare to a dedicated modern tech lens in resolution.

In anycase, I have been using the TSE canon lens. The example of the contax lens is way sharper already to the canon specimen. So, if I can accept Canon's I think I can accept Contax. Hahhaha Thanks though for the fair and valid warning!

 

[gerald.d]

In anycase, I have been using the TSE canon lens. The example of the contax lens is way sharper already to the canon specimen. So, if I can accept Canon's I think I can accept Contax. Hahhaha Thanks though for the fair and valid warning!

What aperture are you shooting the TSE's at? I'd recommend f/11-16 for the best results.

There is a significant difference on the 24 even just between f/8 and f/11 -

Copyright Gerald Donovan 2013. All rights reserved.



Kind regards,


Gerald.

 

[kimyeesan]

What aperture are you shooting the TSE's at? I'd recommend f/11-16 for the best results.

There is a significant difference on the 24 even just between f/8 and f/11 -

Copyright Gerald Donovan 2013. All rights reserved.


Kind regards,


Gerald.

Hi, Gerald, I always shoot f11 or smaller, but I do find that I need to dial the focus back a bit from the end turn of the canon focus ring as it focus way pass infinity... or am I wrong? it realy do have to pair with the Credo50 to check critical focus everytime... even at f11...

 

[gerald.d]

Hi, Gerald, I always shoot f11 or smaller, but I do find that I need to dial the focus back a bit from the end turn of the canon focus ring as it focus way pass infinity... or am I wrong? it realy do have to pair with the Credo50 to check critical focus everytime... even at f11...

You're not wrong - the TSE's focus way past infinity, and the tiniest of movements can make a huge difference. They are very, very sensitive.

Kind regards,


Gerald.

 

[marc aurel]

What aperture are you shooting the TSE's at? I'd recommend f/11-16 for the best results.

There is a significant difference on the 24 even just between f/8 and f/11 -



Kind regards,

Gerald.

Hi Gerald,

I did a detailed comparison of the TS-Es (17mm, 24mm II, 90mm) and the Contax-Zeiss PC-Distagon 35mm on Luminous Landscape Forum (http://www.luminous-landscape.com/forum/index.php?topic=93273.0). I attach a compilation of crops from different parts of images with 10mm of vertical shift. There is more about this on LL.

My recommendation:
• Unshifted position: for a flat subject I would use all lenses at f8. This will change of course if you have a 3-dimensional subject that needs more depth of field.
• Shifted position (+10mm): for a flat subject the PC-Distagon and the 90mm can be used at f8 even shifted. The 17mm and 24mm need to be stopped down to f11 for better corner sharpness. From about 3 or 4mm of shift f11 is better with the 17mm and 24mm.

These tests were for the use on an A7R. Used on an Alpa FPS and a 44x33mm sensor like the IQ 250 you get into the not-so-good part of the image circle too often. That was the reason why I decided to stay with the A7R (or the upcoming 5DsR).

I could get my hands on the Contax 35mm for 645 format on an Alpa FPS and the prototype of the Alpa Shift-Adapter too. I was very impressed. As shown by others in this thread it is much sharper in the outer part of the image circle than the TS-Es. I would say this lens is definitely up to the needs of modern sensors. But I need a wider lens for architecture photography too often. And there is no wider option in the contax system.

Best regards - Marc

 

[narikin]

I understood that. It's the opportunity to use zoom lens, therefore more versatile that draw me to this path.

I used to have that Contax MF zoom - pretty good lens, and not bad value for the glass/ elements involved. Heavy though. No idea if it up to digital or not, sold it many years ago.

All I can say is stay away from current generation Rodenstock Tech lenses. Especially the 90mm HR-SW. You will not be happy with any Contax or Hasselblad lens once you've seen what that can do.

 

[gerald.d]

Hi Gerald,

I did a detailed comparison of the TS-Es (17mm, 24mm II, 90mm) and the Contax-Zeiss PC-Distagon 35mm on Luminous Landscape Forum (A comparison of four shift lenses on the A7R). I attach a compilation of crops from different parts of images with 10mm of vertical shift. There is more about this on LL.

My recommendation:
• Unshifted position: for a flat subject I would use all lenses at f8. This will change of course if you have a 3-dimensional subject that needs more depth of field.

<snip>

These tests were for the use on an A7R. Used on an Alpa FPS and a 44x33mm sensor like the IQ 250 you get into the not-so-good part of the image circle too often. That was the reason why I decided to stay with the A7R (or the upcoming 5DsR).
Best regards - Marc

Hi Marc -

It's very important to stress the sensor here. With the 24 TSE at least, there is a significant difference on FF MFDB when you go from f/8 to f/11, and another improvement from f/11 to f/16.

The diagonal of the MFDB is 14mm longer than that of the A7R, so it's perhaps not surprising that if you're "only" shifting 10mm on the A7R you're not getting into the zone where stopping down starts to make a big difference.

Looking at your test image, I'm assuming that you're shifting up 10mm in portrait orientation - that means the image circle required to cover that shift is actually just 61mm.

The TS-E image circles are a lot larger than that - they have to be a minimum of 67.2mm to cover the IQ180 used in my earlier linked example.

It's great to see these lenses getting used on a wide range of cameras and formats - they are incredibly versatile - but care needs to be taken not to interpret results of tests on one format as being relevant to another. I wouldn't dream of shooting these lenses at f/8 on FF MFDB unless I wasn't at all worried about the corners.

Kind regards,


Gerald.