Hi,
...and the current concept is what came about to replace it.
Let us enter the 'way back' machine and set it to 1994. With a little move laterally in the timespace continuum, we can also shift ourselves to land in Japan. Wher Nikon and Fuji are codeveloping a DSLR based more-or-less on the F4 film camera known as the Nikon E2 and Fujix DS-505.
We'll see that the standard CCD size of the day would have a large FLM, on the order of 5-6x, so they incorporated a reverse teleconverter (RTC) into the front of the camera. That allowed all 35mm lenses to work with the same angle of view as they did with film.
Sounds pretty good, right? Yes, it does, right up until you get to the problems.
First problem: The RTC lenses extended the nose of the camera by a factor of three. It now has the size of a 645 medium format camera.
Second problem: The weight of the extra glass makes it weigh about the same as a 645 as well.
Third problem: Light falloff from the extra optics loses three stops of light.
Fourth problem: recovering from the light loss means that the miniumum ISO is 800, but you can boost it to 3200 (only two steps for some reason I don't understand) if you don't mind images that look like they were taken in a snowstorm.
Fifth problem: Lenses with maximum apertures smaller than f2.8 tend to have vignetting in the corners of the image. Lenses with maximum apertures smaller than f4 tend to result in circular images, much like a fisheye lens, only without the distortion.
While Fuji and Nikon were trying to peddle this wonderful product, Kodak was developing larger CCD chips and bolting Nikon and Canon film bodies onto their cameras. All of the problems noted with the E2 were corrected, but they did have the FLM issue. Of course, the FLM was in the 1.5x region, and most people could live with this.
I also note that Kodak sold a lot more of the $25-30k 6mp units (both Nikon and Canon based) with a 1.3x FLM than Nikon and Fuji sold of their $10k 1.5mp units with RTC's.
The follow-on Nikon D1 and Canon D30 also opted for a half-sized imager and the resulting FLM, rather than accept all the issues associated with trying to use a RTC.
How do I know about all the fun one has with the E2. It's simple. I still have one! Guess how much I use it these days? Right. It does let my wife take some shots of completed designs for emailing to clients. It still works well enough for that, but that's about all.
I think the 'law of physics' you over looked is that the concept stinks in practice. However, you can try it yourself. Just get one of those lens mount to filter ring adapters and reverse mount a 50mm lens. That'll do the same thing. Photographers have been reverse mounting lenses for decades.
It's all about to become a moot point, I think. Kodak has an 11mp 24 x 36mm DSLR imager available these days. How long will it be before someone has that in a product? The chip announced in late June. If co-development of the application (meaning a camera) occured...well... keep a close eye on Photokina.....
Stan
To retain lenses' 35mm angles of view on DSLRs with 1.5 or 1.6
multiplication ratios, couldn't the manufacturers simply produce
the opposite of an extender to be inserted between body and lens?
Or is there some immutable law of physics that I'm overlooking?
What would the effect be on the widest f-stop ratio of the prime
lens?
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mustafa
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Amateur Photographer
Professional Electronics Development Engineer
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