In short: it is a adapter that allows the use of 35mm-foto or cinema lenses
on camcorders to to achieve the typical filmlook that video cameras can't provide.
Traditionally movies were shot on film. Over the years several filmformats
developed which were different in aspect ratio and size. Unlike as in
the video field, where the sensor defines the size and aspect ratio of the image,
on film the image size and aspect ratio can vary in a wide range - as long as
it fits somehow onto the available film. Depending on how the film goes through
the camera the image can be vertical or horizontal. Horizontal image
oriantation was used in 35mm foto cameras. This however is unpractical for
movie cameras with large film spools, thus in them the film runs vertically.
Since the image remains horizontally it can not be wider than tha available
space between the perforations and this defines the image width. This image
size became known as 35mm movie format. All optics have been designed for
this image size and countless movies recorded with it. This rather large
image causes a short deopth of field (DOF), i.e. the distance range from the
lens to the object within which a sharp image is obtained. Everything outside
this range vanishes in fuzziness. This might sound like a drawback but rather
is an advantage, since the director can use this to direct the visitors
attention to certain elements in the picture. With deep DOF the visitor is
easiely confused by to much unnecessary details, not just that, a shorter DOF
also gives a more pleasing, soft look.
Caused by the laws of geometrical optics, the smaller the image sizes (or the
smaller the apperture setting, i.e. bigger f-stops), the longer the DOF becomes.
The result is, that where you can let some things disappere in fuzziness that
you don't want to draw attention to on 35mm film, you can't on 8mm film. Since
8mm is more ore less the same size as the sensors of most video cameras too,
you have the same problem on almost every video camera. This image
characteristic is known as video-look (deep DOF). Even if you could change
the lens of your camcorder (what you can't on most modells) you are still
stuck with the deep DOF. There was no way around (other than using bigger
sonsors as some professional video cams did) until someone came up with a
Why bothering with a bigger sensor ? All that is needed is a bigger image !
So the image was not directly projected onto the sensor, but with a real cine
lens on a 35mm format sized ground glass to create an intermediate image,
which then in turn was imaged onto the sensor with a macro lens. This way the
actual DOF of the camcorder became unimportant. The real image was created by
a 35mm cine lens, resulting in the same image characteristics as known from
35mm film. There it was: film look on video !
With the advent of modern DSLRs however the 35mm-adapters soon dissapeared as
fast as the emerged since DSLRs naturally came with bigger sensors and when
they where able to record film it changed the whole industry. DSLRs not just
killed the 35mm adapters, they are now even about to kill the entire species
of video cameras ! In a few years you will hardly find a real camera anymore
at all ! DSLRs give a very sharp and image, they are rather neutral to
the recorded image (more or less). "That's a good thing" you might think, but
is it ? Do you like to eat only packet soup or listen to music made from pure
sine tones only ? Me not. Clean stuff is lacking any character - and DSLR
images are lacking character. This certainly is good if you want to shoot the
1001th variant of a surgery room story, but not necessarily for everything
"Film look" was not just all DOF related only. Film had a different light
sensitivity characteristic and a righer dynamic range than digital sensors
have, a different color characteristics, it had "film grain" and a sort of
"light diffusion" that happens when you have strongly overexposed highlights
in your image, e.g. when you directly shoot into a light source. This all is
lacking in DSLR images.
A 35mm adapter in turn is not neutral to the image. It has its own surface
structure which can mimic film grain and diffuses the light. The result is a
change in image characteristics. Contrary to common believe the image is not
necessarily less sharp (if you have a good DOF adapter). You have a sort of
"light diffusion" as film has, the brightness characteristics changes more
towards film and the structure of the gound glass adds its very own
characteristics to the image. The result is a much more pleasing, soft image.
To give you a clue as to how 35mm-adapter footage might look like, here is a
collection of the best videos I have found on the web so far:
These days 35mm-adapters are out of fashion since most filmmakers changed
over to DSLRs. Only a few products are still commercially available. Also
almost all webpages describing the technology vanished into the digital
nirvana too. A list of still available products can be found
here. So either you are lucky to get your hands on
one of them on eBay, or you have to DIY. This is not complicated, but not
really easy either. Two guys still manufacture such adapters on request
(IKORD V5, GT35Pro), but the image quality differs significantly since they
use different ground glasses. The IKORD (which uses a Canon Ee-S ground glass)
sometimes might add a very strong own character to the image, while the
GT35Pro, which uses a grinded and coated GG, is way more neutral.
The adapters however have a significant drawback - they are complicated to
handle (you have to control two focus and aperture settings - the one of
your camera, and the one of the adapter). Additionally, the image you see
on the camera is now fliped upside down, so you need a external upside-down
mounted monitor to see the image in the right orientation.
Because of all of ths external hardware you will end up with a huge and heavy
rig which, however, in turn you instantly identifies as a professional
filmmaker to the public. You have no chance to hide ;)
A professional rig with 35mm-adapter is quite costly, even if you DIY (but
still not to compare if you would buy a professional one). But
since film now is dying out eventually completely, this is the second best
choice if you want to have images which stand out from the masses and have
this little "special extra" that others don't have - as film used to do.