Thursday, 12 July 2007

The Hartblei 45mm Super (duper) Rotator (Part 1)


The HARTBLEI 45mm Super-Rotator shift and tilt lens is a unique and remarkable lens, even among shift/tilt lenses. This is a short story of the modification of this lens to create something even more interesting for users of digital SLRs. I first read about this lens on Luminous-Landscape quite some time ago (and I recommend that you do the same if you are interested). When I read the article by Michael Reichmann I was sure I would get one of these lenses. Although they were originally designed for use on medium format (645) cameras, more recently they have also been available for popular 35mm SLR mounts. For those who are not familiar with the specification, the lens offers 12mm of shift in any direction, and 8 degrees of tilt, also in any direction, independent of the shift direction. But time went by and one expense led to another and it never seemed pressing, so it was a considerable while later when I saw a used one on eBay. New lenses ship from the Ukraine, but this one was already in the UK and looked to be gaining little interest. Sure enough I got it for just over £100. It turned out to have a mount for a Contax 645 medium format camera (now discontinued), but at the price I wasn't too bothered because I thought I could get it modified and still make a saving.

I started looking round for converters and also contacted SRB in Luton, who are known for their engineering work on photographic equipment. It turned out that Contax 645 to Canon EOS (my camera of choice) converters were few and far between, but Pentacon 6 to EOS converters were readily available. In fact there were converters that had their own shift movements. An idea started to form. To allow shift movements without vignetting (dark areas near the corners), the lens must have a bigger than normal image circle. Imagine moving a rectangle within a circle. The rectangle must not go outside the circle. If you want to move the rectangle more you will need a bigger circle. This lens has an image circle large enough for movements on a 645 camera, so on a 35mm camera (or equivalent digital) it is not possible to make use of much of the image area that the lens forms. In other words the same movements but with a smaller rectangle will not get as near the edge of the circle. Therefore, much of the lenses huge image circle would be wasted. An extra shift adapter (with 11mm of shift) would be a way of harvesting some of the extra image circle.

Following conversations with Ian Broomhead of SRB, I purchase a Pentacon 6 to EOS adaptor and sent the lens and the adaptor off to Luton for modifications. Unfortunately for me, its arrival at SRB coincided with a large order from another customer, and so there was quite a delay before the lens was returned to me (I gather that it is large volume jobs like this that allow SRB to make one-off adaptors for people like me at reasonable prices). As you can imagine I was eager to try the new contraption. But my very first shots showed a problem. I took a couple of shots inside the house, and saw pronounced flare. But this wasn't normal lens flare. It was fogging, but only in patches. Not what I was used to seeing. The review of the lens on Luminous Landscape had quite specifically mentioned that it handled flare well. Could mine be so different? My guess was that the problem was caused by internal reflections between the digital sensor and some of the flat surfaces of the adaptor. Not too surprising really. The adaptor was designed in the days of film, when such things were not so much of a problem. Digital camera sensors are much more reflective than film and so light can be reflected back towards the lens. If it finds a parallel reflective surface it is bounced back again towards the sensor where it shows up as a foggy patch.


Surprisingly the problem didn't show up all that often (as in the image above, which is made from four shots). Many outdoor subjects were captured without apparent problems, and I was able to become familiar with the use of the lens in a variety of situations. A combination of black flock material, acid etch primer and matt black paint and the lens was ready for another test. So far, despite my best attempts to provoke it, I have not seen the same problem.

So, what benefits come from extending the shift from 12mm to 23mm? Well, of course the lens can be used just as you would any shift/tilt lens, but now there is also a greater potential for stitching a number of frames together to form very large images, and all without the need for any special software as the images will all align perfectly - they are in fact just pieces of the same image from the same lens. I have already made several images well in excess of 40 million pixels from this lens used with a 12 million pixel camera (EOS 5D). Currently the highest resolution digital back is 39 million pixels. Of course that doesn't make the images as good as from these digital backs. Other factors come into play, but for stationary subjects the combination offers a significant resolution boost. One possible limitation that had occurred to me was that of internal vignetting due to the camera lens throat cutting off part of the image. Well, this does occur, but it happens only on parts of the image that tend to overlapp and the darkened edges can be lost in the process of putting the final image together.

Anyone wanting to get one of these lenses only has to purchase one in Mamiya or Pentacon 6 fit and buy the appropriate shift adaptor from eBay. Mine only needed more extensive work because there were no Contax to EOS shift adaptors. Be prepared to have to do a bit of work to cure reflections caused by the adaptor, but if you don't mind doing so you will probably have a very useful lens.

In part 2 I will look at the circumstances in which you would use a lens like this and how to use it (and to some degree why).

Part 2
Part 3

4 Comments:

Anonymous Anonymous said...

Good to see the long-awaited saga of the tilt-shift lens at last!
Andy Sleath

8:26 pm, July 13, 2007  
Blogger John Maw said...

Hi Andy.

Thanks for your comments. Best wishes.

John

9:29 pm, July 17, 2007  
Blogger gazsus said...

I am delighted to come across this old blog entry as I have just bought the same lens, with the same Contax mount, to use on my 7D. I've spent 3 days chasing my own backside around the internet trying to find an adapter to connect the lens with my camera, then I see you have found the solution. I'm going to contact SRB-Griturn (as they are now called) and hopefully I'll have the lens working on my 7D soon. Thanks for sharing.
Gary.

4:54 pm, July 09, 2012  
Blogger John Maw said...

Hi Gary.

I'm glad to have been of some help. These are nice lenses and fantastic value.

All the best.

John

9:28 pm, July 09, 2012  

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