This friday we have a guest author here on Fujirumors. It’s Jan Vogelaar, author of various books like “Contarex, Contax G & Leica M Lenses Guide to Digital Imaging on the Fujifilm X-Pro1” [ebay (click here) or at camerabooks (click here)]. He was so kind to send me an extract of his book.
And don’t worry, Rico Pfirstinger is working on the next X-pert corner articles. Many articles of the X-pert corner are based on Rico’s book ““Mastering the FUJIFILM X-Pro1” (Kindle Edition) (Apple iBook Store) (German version)”. As you may know, Rico is writing all his articles on Fujirumors for free. It would be great if you’d support his great work by purchasing his book. And thanks to all those who already did it.
A book review by Jan Vogelaar
The development of photographic lenses cannot be complete without Carl Zeiss AG. It was Ernst Abbe of the Zeiss Company who first applied scientific principles to the lens design process, rather than relying on trial-and-error experience.
Ever since the lens design principles by Zeiss are given special names, which nowadays, some for more than a century later, are still used: Tessar (1902), Planar (1896), Sonnar (1929), Biogon (1951) and Distagon (1958). In many ways the history of Carl Zeiss AG is the history of photographic lenses. Carl Zeiss has acquired an excellent reputation for its lens quality, mechanically as well as optically.
Another relevant aspect is illustrated in the next picture, showing the light beam projection angle of the Retrofocus and the Biogon lens design. The angle α-1 of the Retrofocus lens is much sharper than the angle α-2 of the Biogon design lens.
Granted permission by Zeiss, full owner of the biogon and distagon design name and (former) patents
Thus, the edge light beams hit the sensor with an angle of 90o minus α-1 for the Retrofocus design and for the Biogon: 90o minus α-2 degrees.
Imagine a small light beam that hits the sensor activating green collecting pixels and the next beam of the same color hits the red collecting pixels next to it, and then a green/magenta color shift may occur.
The sharper the hitting angles the more chance there is for this color shift. This phenomenon occurs with some Biogon (ánd other) lenses.
Although this is not a complete scientific explanation, now you can understand the origin of the different color shifts that now and then appear in your digital pictures more often with the Biogon type of lens design. All colors should be in focus in exactly the same plane e.g. the sensor’s plane.
PIXEL COUNT & RESOLUTION
The requirements for the sensor’s resolution primarily depend on what purpose the photographer has with his pictures. If the aim is to obtain a picture file for maximum enlargement then the maximum resolution is required. The pixel race is mainly a marketing tool, easy to write about and the general public believes the more pixels the better. However, the number of pixels is most relevant for the size of the picture to be printed. 12 mega pixels are sufficient for any 10” x 18” print.
From a resolution point of view the actual pixels pitch and the optical performance of the lens might well be much more relevant for the registration of finest details in the image. In other words, if the lens resolution is capable to define a 6 micron sized detail, the resolution for the sensor should be capable to do the same. The pixel pitch for a 15 – 20 Mp sensor is app. 6 microns.
Definition: The pixel pitch is the distance in mm between the centers of two neighboring pixels in the pixel array.
Today’s sensors are approaching the capabilities of the best lens designs, at least that is the message that lens designers are now broadcasting.
The main factors limiting the lens performance are:
- Aberrations, which lens-designers try to improve ánd
- Diffraction, which basically is a physical phenomenon.
Aberrations: spherical, coma, axial chromatic, astigmatism, field curvature, are very hard to eliminate
with the high-speed lenses.
Diffraction is an optical effect, which softens the total resolution of the photography, no matter how many megapixels the sensor has.
The designer’s success determines how much resolution and contrast is captured. If the aperture is opened wider, the aberrations are increasing with the bigger aperture openings.
Conclusion: The most relevant parameters, that limit the lens performance, given a particular picture size, are the best optical design and the aperture opening. In general: the aperture openings smaller than F = 16 or 22 already come close to the diffraction limitations.
Definition: Light travels in straight lines, however it begins to disperse or diffract when it is squeezed through a narrow opening e.g. the camera’s aperture.
We will leave the technical and physical background information for what it is and now concentrate on what the purpose of this article is:
The goal is to review and determine the real life and practical results and compare the results achieved with a variety of Zeiss Contarex, Zeiss Contax G and Leica M mount lenses. By showing the results for each lens at full opening, at f = 5.6 (on the table) and at f = 8 the variable of diffraction is not really relevant.
A wide variety of adapters are produced, for the Sony Nex mount, the Olympus 4/3rd and micro 4/3rd mount and for the Fujifilm X mount. At the lens end virtually every mount is available:
Alpa / C mount (ø 25 mm) / Canon EF / Canon FD / Contarex / Contax & Yashica / Contax G1 & G2 / Exakta / Leica M / Leica R / Leica screw (ø 39 mm) / M42 screw (ø 42 mm 1 mm pitch) / Minolta MD / Nikon F / Nikon G / Olympus 4/3rd / Olympus OM / Pentax PK / Rollei / Sony / T2 (ø 42 mm 0.75 mm pitch)
The main adapter producers are: In Germany: Novoflex, Voigtländer, in China & Japan: Kipon, Metabones, Rainbowimaging, Rayqual and Photodiox.
Furthermore Fujifilm introduced in June 2012 already a fully coupled Leica M adapter including the focal length selection for the Fuji X Pro 1. The design prevents collapsible Leica lenses hitting the interior of the camera.
The Fujinon XF lenses are newly designed for the APS C sensor. Al other lenses in the book however are originally designed for film. Even many new lenses on the digital market today are a modification of film design lenses.
The scores for all lenses are given on a scale of 1 to 10 for sharpness and brilliance, 10 is best. For Color fringing and color aberration the score is also on a scale of 1 to 10. 10 equals totally absent.
All material is produced in a timespan of about 2 to 3 hours and no post-processing for aberrations or sharpness is performed. All files are .jpg from Photoshop and/or the Fuji .jpg in camera engine.
The Fujinon XF lenses are newly designed for the APS C sensor. Al other lenses in the book however are originally designed for film. Even many new lenses on the digital market today are a modification of film design lenses. These considerations made me select the new Fujinon XF lens for the standard.
THE FUJINON XF 1.4/35 MM PERFORMANCE (specs&price)
This very fast Fujinon XF 1.4/35 mm lens is a pleasure to use. Not the most compact, but still light weighted and an excellent performer.
The center is at f = 1.4 already very sharp: excellent. The very minimal light fall off disappears in one stop. There is minimal chromatic aberration in the very far corner only at f = 1.4. Stopped down to f = 5.6 the chromatic aberrations disappears completely even in the very far corners.
An easy to handle, very fast wide-angle lens living up to all expectations.
Center crop Fujinon XF 1.4/35 mm at f = 1.4
Corner crop Fujinon XF 1.4/35 mm at f = 1.4
Center crop Fujinon XF 1.4/35 mm at f = 8
Corner crop Fujinon XF 1.4/35 mm at f = 8
THE CARL ZEISS CONTAX G PLANAR 2.0/35 MM PERFORMANCE (ebay worldwide via slidoo)
At full opening this Contax G Planar 2.0/35 mm lens is a little bit soft and has almost no light fall off. Fully opened a very good score already.
The performance improves even further by stopping down and the performance is at f = 5.6 really excellent.
Playing with the depth of field and or stopping down to f = 8 brings the performance center to corner up to one’s highest expectations, very close to the norm lens.
If you own this lens: buy the adapter and I am sure you will not be disappointed.
Center crop Contax G Planar 2.0/35 mm at f = 2
Corner crop Contax G Planar 2.0/35 mm at f = 2
Center crop Contax G Planar 2.0/35 mm at f = 8
Corner crop Contax G Planar 2.0/35 mm at f = 8
THE CARL ZEISS BIOGON ZM 2.0/35 MM PERFROMANCE (ebay worldwide via slidoo)
At full opening this Biogon 2.0/35 mm is soft and has (about one stop) light fall off. Fully opened a disappointing score in my opinion.
Although stopping down improves a lot and the performance is at f = 5.6 not yet at its best, just good.
Stopping down to f = 8 or 11 is necessary in order to brings the performance center to corner up to one’s expectations.
Center crop Carl Zeiss ZM Biogon 2.0/35 mm at f = 2
Corner crop Carl Zeiss ZM Biogon 2.0/35mm at f = 2
Center crop Carl Zeiss ZM Biogon 2.0/35mm at f = 8
Corner crop Carl Zeiss ZM Biogon 2.0/35mm at f = 8
THE LEICA SUMMICRON M 2.0/35 MM PERFROMANCE (specs&price)
At full opening this Summicron 2.0/35 mm is mildly soft and has (about one stop) light fall off. Fully opened already a good score.
Stopping down improves a lot and the performance is at f = 5.6 really good.
Stopping down to f = 8 or more brings the performance center to corner up to one’s expectations: excellent!
A great lens to put on the must have list.
Center crop Leica M Summicron 2.0/35 mm at f = 2
Corner crop Leica M Summicron 2.0/35 mm at f = 2
Center crop Leica M Summicron 2.0/35 mm at f = 8
Corner crop Leica M Summicron 2.0/35 mm at f = 8
- The examples in this article illustrate, with perfect compatible pictures, the performance of top quality lenses on the new Fujifilm X-Pro 1 mirror-less digital camera.
- Fujifilm has initiated a new sensor development with respect to the randomization of the sensor’s pixels position and the algorithm that is needed to process the data. The absence of the low pass filter is absolutely an improvement.
- Fujifilm has designed new lenses that are not anymore modifications of the film lens design. The Fuji lenses cannot be used on any other camera system, although the design seems to me a further development of the Distagon (retrofocus) concept.
- All lenses in the book are mechanically beyond questioning. Carl Zeiss and Leica are still top class producers. The quality of the adapters is at a sufficient good level.
- For the photo enthusiasts, camera and lenses collectors, the digital photography era brings new challenges and opportunities. The proof is here in the book. The oldest Leica M lens in the book is the Elmar 2.8/50 mm of the production the year 1958. A few of the vintage Contarex lenses have a similar age.
- Of course the optical systems have seen many improvements over the years. The developments of multi-layer coating techniques, high dispersion optical-glass ánd a-spherical lens elements, certainly are worth mentioning. If you own vintage lenses: Select one of the digital camera systems as discussed in the book, select the right adapter and start using your precious optical glass.
A BRIEF DESCRIPTION OF THE BOOK’S CONTENTS:
After the Introductory chapters you will get to see the results of a collection of 28 lenses.
- You can check the Carl Zeiss Contax G: 2.8/21, 2.8/28, 2.0/35, 2.0/45 and 2.8/90 mm.
- There is absolutely NO need to trim the protection cams at the rear end of both the wide-angle 21 and 28 mm Biogon G lenses. The mounting of the lens is explained in the book.
- And the famous Contarex 4.0/18 mm Distagon all up to the 4.0/250 mm long Tele Sonar including all the Contarex lenses in between. 16 Carl Zeiss Contarex lenses all together.
- Also the Carl Zeiss Monocular 80 x 30B combination with the 50 mm & 135 mm is not forgotten: imagine a 1060 mm tele on your digital camera. Multiplied by crop-factor 1.5 makes 1590 mm …
- Furthermore the Leica M Summicron: 2.0/35, 2.0/50 and 2.0/90 mm, a Summaron 2.8/35 mm and the Elmar: 2.8/50, 4.0/90 and 4.0/135 mm.
- Including the Zeiss ZM: 2.0/35 and 2.0/50 mm as well.
- Beautiful, 59 full-color images evaluate and illustrate full size and with center & corner cuts, what the essential strengths and weaknesses of the lenses are so you will quickly find out how to select and use your lenses like a pro.
- All is together on 98 pages, 77 in full color in this very complete and interesting book.
- Last but not least a DVD with more results (150 comparable photographs) at full open, f = 5.6 and f = 8 comes together with the book. The performance of the same lenses on film are on the DVD as well.