{"id":11609,"date":"2018-02-18T12:30:57","date_gmt":"2018-02-18T11:30:57","guid":{"rendered":"https:\/\/phillipreeve.net\/blog\/?p=11609"},"modified":"2026-01-14T09:29:28","modified_gmt":"2026-01-14T08:29:28","slug":"review-carl-zeiss-28mm-f-2-8-biogon-t-1-5m-pcx-filter","status":"publish","type":"post","link":"https:\/\/phillipreeve.net\/blog\/review-carl-zeiss-28mm-f-2-8-biogon-t-1-5m-pcx-filter\/","title":{"rendered":"REVIEW: Carl ZEISS 28mm f\/2.8 Biogon T* + 1.5m pcx filter"},"content":{"rendered":"

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The Contax G 28mm Biogon was considered one of the best 28mm available on film, but suffers serious issues on digital due to sensor cover glass. Can a simple filter make the lens a competitive performer on Sony cameras? Find out below.<\/p>\n

I have shot this lens for years on the Sony A7 and more recently with a PCX filter and then on a Kolari UT modded A7. Unless otherwise noted, all of the tests in this review were performed on a Sony A7RII with a reversed 1.5m PCX filter on the lens (Thanks again to Nehemiah<\/a> for lending me the A7RII). Check captions on sample pictures to see what camera was used. Bonus: The Contax G 28mm Biogon is both Phillip and my favorite lens on aps-c cameras, so I will also add a second installment later reviewing the lens for aps-c provocatively titled How the A6000 + Contax G 28\/2.8 is better than an RX1<\/em>.<\/p>\n

Sample Images<\/h1>\n
<\/a>
Sony A7 | Carl Zeiss Contax G 28mm f\/2.8 Biogon | f\/2.8<\/figcaption><\/figure>\n
<\/a>
Sony A7 | Carl Zeiss Contax G 28mm f\/2.8 Biogon | f\/8<\/figcaption><\/figure>\n
\"Sony<\/a>
Sony A7 | Carl Zeiss Contax G 28mm f\/2.8 Biogon | f\/11<\/figcaption><\/figure>\n

<\/p>\n

Specifications<\/span><\/h1>\n\n\n\n\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t
Diameter<\/td>56mm<\/td>\n<\/tr>\n
Length<\/td>31mm (+ 3-6mm for PCX filter)<\/td>\n<\/tr>\n
Filter Thread<\/td>46mm<\/td>\n<\/tr>\n
Weight<\/td>150g<\/td>\n<\/tr>\n
Max. Magnification<\/td>1:15<\/td>\n<\/tr>\n
Close Focusing Distance from the sensor<\/td>50cm<\/td>\n<\/tr>\n
Number of aperture blades<\/td>6<\/td>\n<\/tr>\n
Elements\/ Groups<\/td>7\/5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n

More information in Zeiss\u2019\u00a0official data sheet<\/a>.<\/u><\/p>\n

Versions<\/h1>\n

There is only one version of this lens. It comes in two colors: Titanium and black but black is much rarer (and more expensive).<\/p>\n

Compatibility<\/h1>\n

The Carl Zeiss Contax G lens line was originally developed in the mid 90\u2019s for the Contax G1 and it\u2019s successor the Contax G2. Both are AF rangefinder cameras.<\/p>\n

Adapting Contax G\u00a0lenses to modern digital cameras comes with two challenges<\/strong>.\u00a0Since the Contax G cameras\u00a0have a rather short flange focal distance of just 29mm you\u00a0cannot adapt them to DSLRs<\/strong>. The advantage of this short flange focal distance is that adapters for mirrorless systems are only about 11mm thick. The other problem is that the\u00a0lenses do\u00a0not have a focusing ring<\/strong>, just AF coupling so\u00a0the\u00a0adapter must provide some means to focus the lens<\/strong>.<\/p>\n

There are two kinds of adapters, purely mechanical and electronic adapters.<\/p>\n

Mechanical adapters<\/strong>\u00a0are available for EOS M, Fuji X, M43 and Sony E-mount. They come with their own focusing ring. They\u00a0range in price<\/u><\/a>\u00a0(affiliate link) from $25 to $140. I own the Kipon one (or possibly a cheap knockoff since I got it second hand for ~$30) and it works fine on all the lenses but the 90mm (which I had trouble focusing accurately at near distances with). Focus is a little rough and in the wrong (Nikon\/Pentax) direction, but perfectly serviceable. I have heard good things about the Metabones and Fotodiox Pro adapters but I haven\u2019t used them personally.<\/p>\n

The\u00a0Techart TA-GA3 adapter<\/strong>\u00a0is very interesting because\u00a0you can use\u00a0AF with newer Sony E-mount cameras<\/strong>! AF with the Sony a7, a7r and a7s is unusable (very slow and unreliable) but with the newer cameras it works quite okay most of the time and gives you all the quickness and accuracy of a screw-drive AF lens on a dslr from 2005 (if you have used one of these you will know what I mean).<\/p>\n

The AF experience is certainly not as smooth as with native lenses. The screw driven\u00a0AF is rather loud<\/strong>\u00a0and while\u00a0it\u00a0tracks small changes in focusing distances well<\/strong>\u00a0it is\u00a0quite slow to realize larger changes in focusing distance<\/strong>.\u00a0Reliability<\/strong>\u00a0was mediocre and\u00a0not near the same level as the native lenses<\/strong>. It also\u00a0fails when it is a bit darker<\/strong>\u00a0in situations where native lenses still work reasonably well. I it found unusable, but then that performance level of AF is what drove me to manual focus in the first place, and some people seem to use it without major complaints. I changed to manual focusing which is realized with a small wheel at the 2 o\u2019clock position. Manual focusing with this method works better than I would have expected but can be a bit fiddly at long distances.
\nThe Techart TA-GA3 adapter sells for about $250 at\u00a0<\/em>ebay.com<\/u><\/em><\/a>\u00a0or\u00a0<\/em>amazon.com<\/u><\/em><\/a>\u00a0(affiliate links).<\/em><\/p>\n

Build\u00a0Quality<\/h1>\n
\"Carl
Carl Zeiss Contax G 28mm f\/2.8 Biogon disassembled<\/figcaption><\/figure>\n

The Contax G 28\/2.8 feels very nice and solid.<\/p>\n

The barrel is made of aluminum.<\/p>\n

All markings are engraved.<\/p>\n

The Biogon\u00a0is made in Japan.<\/p>\n

I have<\/em> disassembled the lens and while it is well engineered and made mostly of metal it does not seem as robustly constructed as typical Leica, Zeiss, and Cosina\/Voigtl\u00e4nder manual focus rangefinder lenses. I would expect it to be more likely to develop problems due to a sudden impact than the previously mentioned manual focus rangefinder lenses.<\/p>\n

Size, Weight and Handling<\/h1>\n