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20mm Minolta versus 21mm Contax Biogon lense

P

picturetaker

I did a comparison from the 20mm AF lense to the 21mm Biogon G Lense from Contax.
The Mionolta lense is very good, the projectet slides are sharp, unfortunately not with aperture 2,8 were this Minolta lense shows lack of sharpness. Close it a lest to 5.6.
Minolta Lense 20mm @ 2,8




Minolta 20mm @ f8




Contax G Biogon 21mm @ 2.8




Contax G Lense Biogon 21mm @f8
 
This ratings are very often just a fake. e.g. Leica 24mm lense with not so good !?, It is hard to belive !
Also there are just a few ratings 10-20, its not enoght.

The Contax 21mm Biogon lense is sharp @ 2,8 were Minolta 20mm @ 2,8 is no good when you wannt a large print.
 
The Minolta 20mm Lense cant be used for Large prints, or you have to close aperture at least to 8.
I would consider a Sigma or Tamron lense if you wanna buy such a 20mm Lense.
I would rate this lense as not so good and compared to a Contax lense as a bad way spending money.
 
I don't know which Minolta 20mm everyone here had been using, but mine back in 1986 was - and remained for the 15 years or so I had it - extremely sharp wide open, and a good match for the Biogon. Admittedly I only ever had the Biogon for any length of time in Contax G form, which is supposed to be better than the reflex Biogon. The Minolta was also much better (by far) than the Leitz 19mm f2.8.

The Minolta 20mm with a bad reputation is the MD 20mm f2.8, which was redesigned from the earlier (unrivalled, superb) MC 21mm f2.8. The 21mm f2.8 had internal floating elements, a Distagon-type design, and a 72mm front thread. It had superb full aperture performance, very good close up flatness of field, and very even illumination thanks to the generous design in terms of optical real estate. The 20mm f2.8 MD suddenly shrunk the lens to fit a 55mm filter thread and went 'Pentax size' (or Olympus size) in proportions. The result was a lens with severe moustache-type distortion, strong vignetting to the corners, and poor full aperture sharpness. Professional Minolta users, myself included, criticised it heavily. Most switched to using the 17mm f4 instead, despite the loss of speed and the higher distortion levels than the old 21mm. It was essentially a traditional large retrofocus design uncompromised by attempts to miniaturise.

In 1985 - only five years after the MD design 'replaced' the big old 21mm - Minolta unveiled the 20mm f2.8 AF and everyone breathed a sigh of relief. The good old Distagon 'bucket' style design was back in; internal floating group to correct close focus; large front element for superior illumination; low distortion; back to 72mm filters. It tested out as a fair match for the old 21mm, putting Minolta back on top with one of the best faster aperture wides on the market.

It was, also, part of a set of lenses which used coatings and glass types to give almost perfect colour balanced transmission (with 3CC/LB units) from 16mm to 500mm - combined with matched contrast. The AF lens system from 1985/6 was the first and possibly only still camera lens system built to the same colour/contrast consistency as professional movie lenses (where colour shifts from scene to scene were unacceptable). Minolta started doing this around 1975, when the XE-1 was launched and used the first shutter/transport mechanism to be compatible with Wess pin register mounts without requiring a pin register camera. We used Minolta for audiovisual production exclusively because it allowed animated sequences in the field. Wear and tear may make the XE-1/XE-5 with the Copal Leitz CLS Shutter less accurate if bought today, but in its time this was the most accurate shutter ever made, and the only one which spaced frames precisely.

That is the sort of heritage the 20mm came from after the 'blip' in Minolta design philosophy represented by the X-700 line (an attempt to match Canon's synthetic resin body and lens production introduced with the AE-1). The 9000 AF and the entire 1st generation lens line were an attempt to return to the values of 1975. I think, in the lens range, they almost succeeded in some respects, and outdid 1975 in others.

Sony had decided to continue making the 20mm f2.8 AF lens, which is pretty remarkable - 22 years down the line after its first announcement.

I've tested the Sigma 20mm f1.8, 24mm f1.8, 18mm f3.5. Tamron do not make now, and have never made, a 20mm f2.8 though they did have a 20-40mm zoom. None of these come anywhere close to the quality of the Minolta 20mm f2.8.

David
 
don't know which Minolta 20mm everyone here had been using, but mine back in 1986 was - and remained for the 15 years or so I had it - extremely sharp wide open, and a good match for the Biogon. Admittedly I only ever had the Biogon for any length of time in Contax G form, which is supposed to be better than the reflex Biogon.>

How can you make a justifiable comparison with such a well accepted lens as the Biogon 21mm/f2.8, when you only had it for a short period of time.

Wear and tear may make the XE-1/XE-5 with the Copal Leitz CLS Shutter less accurate if bought today, but in its time this was the most accurate shutter ever made, and the only one which spaced frames precisely. >

Did you compare this shutter to Compur Syncro or Prontor shutters?

Regards:

Gilbert
 
I can make justified comparisons because my job was testing lenses. It's hardly heretical to suggest that Minolta's design for the 20mm, a result of close working with Leitz in the 1970s on aspherical elements and floating groups and the product of ten or more years of development, should have been a fair match for the Biogon, even though the first modern version was introduced in 1995 some ten years after the Minolta. The Biogon is still based on a very old design concept.

The Biogon is a symmetrical lens which exhibits typical high central sharpness (even the 20mm f5.6 Russar, based on the original Biogon design of 60+ years ago, offers that). It is not distortion free but because it's a rangefinder lens the distortion is purer, plain barrel rather than compound. It has strong optical vignetting, a characteristic many users like because of the 'holding in' effect, though it can cause problems when cropping images. The 21mm today is a Cosina-made lens of excellent quality, and I wouldn't rate it as better than the 20mm f2.8 Minolta, just different. I suspect it's actually better than the Contax G variant made by Kyocera, but I had a mixed relationship with my Contax G lenses. They seemed extremely sharp and had a pleasant fluid quality to the image, but the camera never seemed capable of focusing the lens accurately enough to use the lens qualities.

How can you compare the Copal Leitz CLS with a Compur of Prontor? Both are leaf shutter, in lens. The CLS was a laminar blade focal plane shutter. As such it set new standards for that type of shutter, which were as it happens higher than those for Synchro Compur or Prontor SVS, as neither could achieve 1/1000th and suffered from the usual failings of leaf shutters at 1/500th.

David
 
usual failings of leaf shutters at 1/500th. >

Usual failings?

and I wouldn't rate it as better than the 20mm f2.8 Minolta, just different. I suspect it's actually better than the Contax G variant made by Kyocera, but I had a mixed relationship with my Contax G lenses.>

So you really don't know!

The Biogon is still based on a very old design concept. >

The Tessar, Planar over 100 years old, Sonnar, 1930. They are all still being used including the Biogon, Distagon, in advanced cameras, film and digital, as well as cinemaphotography. So, what does old design have to do with anything?

Leitz in the 1970s on aspherical elements>

Zeiss had aspherics in 1936!

Regards:

Gilbert
 
Well, you clearly have an agenda, and nothing much to do with Sony/Minolta. Leaf shutters are at their least efficient working at wide apertures, and also at their least accurate at high shutter speeds. Since wide apertures and high shutter speeds often go together, the failings are well enough known (graph of lens transmission value expressed by aperture created by shutter during opening and closing phases mapped over time - etc).

I guess one thing I can use to judge the Biogon in retrospect would be the pictures I took at the Zeiss conference in Majorca when the G1 was launched. I used the 16mm and the 21mm a good deal. The Fujichrome 50 slides do not show any increase in detail or sharpness compared to any of the many I shot with the 20mm Minolta at the same period. All they do show is far more visible light fall off to the corners (with the 16mm, I used the centre filter).

The point of course is not that old designs are bad - all modern designs are derived from a handful of originals - but that modern designs using methods and materials unavailable in the past may be better. In the case of the Minolta 20mm f2.8, close focus distance quality is specifically very much better than any straight Distagon design. Hasselblad did address this, and I owned and used for a long time a Distagon 40mm CF with a manually adjusted floating group. The Minolta floating group is coupled to the focus.

David
 
Well, you clearly have an agenda, and nothing much to do with Sony/Minolta.>

David
photoclubalpha.com>

Agenda, looks to me like you have one!

Also, you are the one that mentioned Zeiss lens designs, and Contax.

You have made a number of unfounded statements today as fact not opinion!

The Fujichrome 50 slides do not show any increase in detail or sharpness compared to any of the many I shot with the 20mm Minolta at the same period. All they do show is far more visible light fall off to the corners (with the 16mm, I used the centre filter). >

How do you know if you had trouble focusing?

Regards:

Gilbert
 
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