Super Angulon XL 38, Super Angulon XL 47 or Apo-Helvetar 48 ?

Hi everybody,

<p>I am planning to go with an Alpa TC, shooting film (6x9). I need some advice

on which lens to start with. I am planning to mainly shoot landscapes,

cityscapes and scenics. As I was surfing through the Alpa-site, I thought of one

of the following:

<p><i>Super Angulon XL 5.6/38

<br>Super Angulon XL 5.6/47

<br>Apo-Helvetar 5.6/48</i>

<p>Which one offers the sharpest results, best color/tonality and best contrast?

Would you suggest something completely different from Schneider?

<p>Please let me ask <b>another question</b>: As I read so far, the difference

between the Super Angulon XL 47 and the Apo-Helvetar 48 is, that the Helvetar is

optimized to be used at f11, while the Super Angulon is optimized for f22. Is

this the only difference? Would this mean, that the quality of the results of

the Helvetar would be inferior when shot at e.g. f22 for landscapes?

<p>Thanks a lot and kind regards,

<br>Thorsten

Thorsten,

I would get the Helvetar as it is better wide open. Most all these lenses will be similar stopped down. Get the 38mm if you really want to go wide, but the 48mm should be a great perfect lens on this camera. Do you really need the extra coverage of the 48mm XL? Please...let me know how you like the camera when you get it!

Emile/www.deleon-ulf.com

I think it comes down to what you would like to do with the lens. The Schieder 38 and 47

XL are large format lenses with large image circles. ALPA has adapted them for medium

format use, so the center area 'sweet spot' is in use. Still as you mention they are best

stopped down. If you were going to look at the SWA model with its 'shift' feature they

would have an advantage with the extra coverage.

I have a 48 Hevatar and it is simply put a great lens. Very usable at its wide apertures and

amazingly good with it stopped down to f8-11. A good combination with the 6x9 back as

the ALPA general use lens. With the usable better corrected f5.6-f8 aperture range of the

Helvetar the ALPA makes a better 'hand-held' camera.

The Schneider datasheets for the 47 mm Super-Angulon (http://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=168&IID=1841) show the stoped-down performance at f22, but that doesn't really mean that for your usage that the optimum stop is f22. Schneider's main design goal was 4x5 photographers, and Schneider was probably stopping the lens down to get the coverage as wide as possible, to an incredible 120 degrees (166 mm diameter). Probably the performance for medium format is excellent at some wider aperture.

Not having heard of the 48 mm Apo-Helvetar, I did a google search and found http://www.alpa.ch/alpa/helvetar.htm, which states under "What Makes it so Special?" "One of the most interesting facts concerning the Apo-Helvetar, based on the legendary Schneider Super-Angulon's design, is that it can be really used at f 5.6 - in any case it is MUCH better at f 5.6 than all large-format lenses (which are optimized for enhanced image circles and for f stops of f 11 and more)".

That page also has a link to a datasheet for the 48 mm f5.6 Apo-Helvetar. At first glance, the MTF curves are very different from those of the 47 mm f5.6 Super-Angulon XL, but when you compenstate for the graphs being plotted for different image circles, the f22 MTF curves become are virtually the same! The f22 curves for the Apo-Helvetar end at the radius 49.5 mm. At this radius the 20 lp/mm radial curve is at 60% and the tangential curve is at 30%. The f22 curves for the Super-Angulon XL are plotted to radius 83 mm, so we have to read the curves above the x-axis value of 49.5/83 = 60%. The Super-Angulon 20 lp/mm curve radial curve is 60% and the tangential curve is about 25%. If you only look at the inner 60% of the MTF curves of the 47 mm Super-Anguon XL, the curves look alot better.

However, the MTF curves for f5.6 are more different, even after compensating for being plotted to different radii. For example, the 20 lp/mm curves of the Apo-Helvetar fall to 40% to 45% from 30 to 40 mm radius, while the sames curves for the Super-Angulon are below 25% response.

After that, the datasheets are identical. Both lenses are 48 mm lenses! The datasheet for the 47 mm SA-XL discloses that the actual focal length is 48.0 mm. The cross-section diagrams of the two lenses look identical. The values of seven other optical parameters are exactly equal, e.g., for both lenses the principal plane separations are HH' = 24.8 mm, the pupil magnification is 0.995, the Back Focal Length is 29.5 mm, etc.

The graphs for Relative Illumination and Distortion on the datasheets for the 48 mm Schneider ALPA Apo-Helvetar and the 47 mm Super-Angulon XL are exactly identical. They forget to crop the graphs for the Apo-Helvetar -- they go to radius 83 mm, showing the lens to cover diameter 166 mm!

It's seems that the 48 mm Schneder ALPA Apo-Helvetar and the 47 mm Schneider Super-Angulon XL are the virtually same lens. When ALPA says that the 48 mm Apo-Helvetar is "based" on the "Super-Angulon's design", they don't mean in some loose sense! They seem to have made some small modification to improve the performance in the center of the image at wide apertures.

If you believe the MTF curves on the datasheets, these two 48 mm lenses (the 47 SA-XL is really a 48 mm lens) are essentially identical at f22 and the Apo-Helvetar is better at f5.6. Guessing, whatever tinkering they have done has reduced the coverage of the Apo-Helvetar somewhat -- otherwise the idea would have been incorporated in the design of the SA-XL.

Sorry for answering so late, but I have been away for a few days. Thank you all for your answers. Michael, thanks a lot for review of the MTF curves. Well, I think you could say, that the Helvetar is a good lens to go with, if you plan to stay with the Alpa (well, that's for what it is designed).

Regards,

Thorsten