Article about obvious Panasonic AF100 design flaw.
Below are some first test shots we were able to perform after getting AF100 camera. We will write a full review soon but now we would like to focus on only one thing that caught our attention. This is something that for some users (like us) is a source of HUGE disappointment and a deal breaker.
Watch the video as this phenomenon is easier to understand and notice in a moving image. Below tests were performed in less than ideal conditions, we don’t have a lab to perform a truly scientific tests. However, we think that below test reveals a pretty serious problem that Panasonic AF100 has.
AF100 sensor flare from Mateusz Broughton on Vimeo.
Few words about Panasonic’s AF100 background.
Panasonic AF100 is advertised as a camera that offers extreme flexibility because of its capability to mount very wide range of lenses. Big sensor size and short flange focal distance of the camera allow use of motion picture and still photo lenses, in addition to lenses designed specifically for Micro Four Thirds system.
Our excitement was huge but… didn’t last very long. Look at the screen grabs below and notice a green ghost in the image. Our first thought was that it is simply a lens flare. Unfortunately it is not. It is not a lens flare, it also is not a kick back from a UV filter which looks very similar to this phenomenon (we did not have a UV filter mounted). What it unfortunately is is an internal reflection coming from the camera’s sensor unit. This phenomenon has been known for years and many DSLR cameras suffered from it.
Sensor Flare / Sensor Ghosting / Sensor Reflection (we will use those term interchangeably).
Surface of the CCD or CMOS sensor is a reflective surface. When light hits the sensor some of it is being reflected, travels back to the rear element of the lens, reflects from it, travels back into the sensor (this “light ping pong” continues but with every reflection intensity of it decreases or the image “lands” outside of the sensor or/and the rear element of the lens).
It is illustrated below (please forgive me a very schematic drawing, such lens woulnd’t be any good !). 
It depends on the quality of the lens coating, the shape of the rear element (flat rear element tends to make the problem worse), distance between the sensor and lens’s rear element, and – what seems to be the problem in case of AF100 camera – reflectiveness of the sensor surface (and/or in case of AF100 additional built in filter that seals the sensor).
Digital revolution forced manufacturers of lenses to change their design to minimize this side effect. Many wonderful lenses still available (Nikkor, Leica, Zeiss, Canon, Kern) were designed in a film era. Because a surface of the film is not as reflective as a surface of the digital chip it has not been an issue.
But wait… haven’t we been successfully using manual focus Nikon, Leica or Zeiss lenses on DSLR cameras? Why all in the sudden the same lenses cause a problem? Isn’t AF100 supposed to be designed with filmmakers in mind (unlike DSLR’s) and is advertised as camera that “can mount it all” ? In all ads the AF100 body is surrounded by lenses made by different manufacturers and originating from different systems.
Comparison with DSLR (Canon 7D).
We shot some comparison tests with 7D camera. Same lens was mounted on Panasonic AF100 camera and then on Canon 7D DSLR. We used specific adapters (both adapters have no glass elements). We used the same Nikkor 50mm f/1.8 AI-s lens that causes the most severe problem.
On Canon 7D camera we can see that ghosting caused by the sensor is MUCH more under control. It is not only its intensity but also its color and saturation. In this particular shot it simply blends with the color of the flame better, therefore is less distracting (watch the video to fully understand it.)
Maybe it is not Panasonic’s fault ?
DSLR cameras are optimized for longer focal flange distance (distance between sensor/film surface and lens mount) and even though this distance still varies depending on lens manufacturer (Nikon F mount 46.50 mm, Canon EF 44.00 mm ) it is not as significant as the difference between Micro 4/3 focal flange distance and i.e. Nikon distance, therefore we can successfully use Nikon, Yashica/Contax, etc. lenses on our 7D, 5D cameras.
Since Panasonic designed this camera as an open platform then maybe they can’t optimize the sensor to work with lenses of different focal flange distances? Maybe our collection of Nikon, Zeiss, Leica lenses is simply not to the standard that AF100 demands?
We thought that then probably a native lens system, designed specifically for Micro Four Thirds system should work fine ( we thought then it was not fair to advertise the camera as one that can “mount it all”). It unfortunately is NOT the case here either. We tested Pansonic’s 14-45mm lens with the camera and… we can see the same ghost! A truly haunted AF100! If it is not optimized to work with its native lens system then what lenses should we use? Look at the ghost seen in the screen grab below. It is clearly not a lens flare but a mirror /flipped image of the brightest element seen in the frame. You can clearly see the shape of the light bulb and even see a description of the bulb at the tip of it!
Look at some other examples. In another test we filmed a high contrast image. You can see a green ghost in both screen grabs shot with Lumix 14-45mm (top), Nikkor 50mm f/1.8 AIS (middle), and almost no ghost in video shot with 7D with the same 50mm lens (bottom). 
More ghosts!
After discovering this problem we looked at the AF100 videos available online and … WE FOUND MORE GHOSTS! Even in one of the very first videos shot by Philip Bloom (lighting a cigar) we can see that green ghost. It is so easy to confuse it with regular lens flare and went unnoticed for quite a while, but look closely and you will see that it is not just a regular lens flare! Virtually any video shot with AF100 available online shot in low light, that has strong sources of light has that problem!
This issue is very severe and will ruin a lot of otherwise beautiful shots. It could be a problem in many shooting situations that involve high contrast images such as blown out windows, snow, sun in the frame, etc. We don’t need ghost in our shots! They are distracting! Panasonic, go back to a drawing board!
Built in ND filter cure???
What is even stranger is that when you use a built in ND filter most of the ghosting is gone! Just try to dial setting 2, 3 or 4 (compensate the exposure with either ASA setting or lens’s f stop) and you will see that it helps Nice! But…. why would you want to use an ND filter when you are shooting in low light (where the ghosting is most visible) ? It is not a solution then. It just doesn’t make sense, Panasonic!
Our speculation is that built in ND filter accidentally works as a cure for described sensor flare issue. It is probably due to the fact that surface of the ND filter has its own coating that prevents sensor flare issue. Again, we don’t have a lab and are not engineers to know exact answer, those are only speculations.
Conclusion.
What this all means is that Panasonic AF100 camera is a prototype! Yes, it is. How else can you explain it if the camera has been released without thorough testing? Maybe we should get paid for testing it? It really hurts that we can’t use the camera with our favorite lenses. It hurts that we can’t use it with any lenses! It is camera’s fault not the lenses and using higher quality lenses such as PL mount Zeiss Ultra or Master Primes will not solve the problem (don’t forget that those lenses were not designed with digital camera in mind either). Even lenses designed specifically for this system cause the problem simply because it is a DESIGN FLAW of the camera.
