GH1 vs 35mm Academy Aperture

Glenn Przyborski

Glenn Przyborski

Member
I though this might be of interest to forum readers, since most people shoot DLSR video to achieve a "filmlike" depth-of-field.

I took a piece of 35mm, academy aperture negative and laid it next to the GH1's imager. The film image is only a couple millimeters larger. Over the past 7 or 8 years, it's become popular to shoot full-aperture 35, but academy aperture (which is offset horizontally to allow room for the optical soundtrack) is still the most popular format. This is due to the fact that most older 35mm cameras have no provisions to re-center the lens mount without permanent modification and collimation. Also, many older lenses, such as the Angenieux 20-120 & 25-250 can't fill a full aperture image without vignetting.

When shooting 16x9 HD, both the film transfer scanner (and the GH1) ignore the top and bottom of the image. You could make the argument that the depth-of-field characteristics of the GH1 are very similar to 35mm academy aperture, movie film.

The 5D's much shallower depth-of-field is like the VistaVision format which moved film horizontally through the camera's gate with each frame being 8 sprocket holes wide. This is virtually identical to the 5D's full-frame 36mm x 24mm imager.
 

Attachments

  • 35negative_vs_GH1.jpg
    35negative_vs_GH1.jpg
    66.4 KB · Views: 0
Glenn Przyborski said:
I though this might be of interest to forum readers, since most people shoot DLSR video to achieve a "filmlike" depth-of-field.

I took a piece of 35mm, academy aperture negative and laid it next to the GH1's imager. The film image is only a couple millimeters larger. Over the past 7 or 8 years, it's become popular to shoot full-aperture 35, but academy aperture (which is offset horizontally to allow room for the optical soundtrack) is still the most popular format. This is due to the fact that most older 35mm cameras have no provisions to re-center the lens mount without permanent modification and collimation. Also, many older lenses, such as the Angenieux 20-120 & 25-250 can't fill a full aperture image without vignetting.

When shooting 16x9 HD, both the film transfer scanner (and the GH1) ignore the top and bottom of the image. You could make the argument that the depth-of-field characteristics of the GH1 are very similar to 35mm academy aperture, movie film.

The 5D's much shallower depth-of-field is like the VistaVision format which moved film horizontally through the camera's gate with each frame being 8 sprocket holes wide. This is virtually identical to the 5D's full-frame 36mm x 24mm imager.
Click to expand...


Awesome Glenn.

Glenn can I use that GH1/35mm film image on my site to illustrate this visually?


Michael Pappas
http://www.pbase.com/Arrfilms
Arrfilms@hotmail.com
http://www.PappasArts.com
 
That filmstrip, as Glenn said, is showing the 4x3 frame from film (and yes, for those who don't know, 35mm film is a 4:3 format, which is the whole reason television was 4:3 in the first place!)

The top and bottom get matted to black (essentially letterboxed) leaving a 1.85:1 image in the center.

As Glenn said, the film frame is offset to the side, shrinking its size some to make room for the optical sound track. So even though the film is 35mm from outer-edge to outer-edge, the actual imaged area in 35mm movie cameras is much, much smaller. The room from sprocket-hole to sprocket-hole is about 24mm, but (as the photo above shows) not even all 24mm is used, a couple of mm are set aside (on the right of the frame up above) for the soundtrack. So the remaining image is about 22mm x 12mm.

The GH1, while not having 100% the same size, is still pretty close; in 16:9 mode it uses an imaging area of about 19mm x 10.7mm. That puts it close to 35mm cinema film, and about 4x larger than a 2/3" video camera's sensor.
 
Last edited:
if im not mistaken, in regards to the acadamy 35mm 4x3 frame, arent anamorphic lenses commonly used so to still utilize the entire frame - not just letterbox it to arrive at the 1.85:1 ratio?
 
Hmm. 22mm, 12mm, sprocket holes, 4x3 frame, academy 35mm, 1:85 ratio matted to black, room for the sound track, 1.3x crop, 1.6x, 1.5x, 1.01101x.

Most important question: will it make me Steven Spielberg?
 
no device will make you spielberg. spielberg is spielberg becuase he had brilliant stories to tell. and someone with a lot of money to produce his vision.
 
sam rides a mtb said:
if im not mistaken, in regards to the acadamy 35mm 4x3 frame, arent anamorphic lenses commonly used so to still utilize the entire frame - not just letterbox it to arrive at the 1.85:1 ratio?
Click to expand...

All 35mm theater release prints allow room for the optical soundtrack. Cinemascope or Panavision anamorphic films expand the top & bottom of each frame and horizontally squash the wide-screen image.

As far as the camera filming the movie, you can either use anamorphic lenses (usually rented from Panavision) or you can use a full aperture and ignore the top & bottom of the image you're filming. Then in final post-production, the top & bottom are masked and the remaining wide format image is compressed horizontally before being printed. Many wide-screen features are shot with cameras that are designed to only pull down 3 perfs instead of the normal 4 perfs per frame. This allows standard lenses to be used for wide screen filming and it also saves film stock. The first use of this technique was called "Techniscope".

An additional clarification regarding 35mm camera apertures... It's not unusual for a camera to have a "full frame" aperture even though the film is being framed for academy aperture projection or scanning to video. The extra image that ends up on the negative is simply ignored. Full frame apertures are "safer" in that a tiny hair or piece of dirt has less chance of ending up in the actual scanned picture area.

I started this thread with regard to 35mm film that's shot for TV release... ie: commercials or TV shows. Projects designed for TV never use anamorphic lenses.
 
Isn't the sensor on the GH1 a native 16x9 chip?

35mm film and digital really are too different worlds in a sense.

I liked the anamorphic look of the Iscorama on the 5D. When you have a lens / chip combination as pretty as that, for that price, in terms of that simplicity and format, the history of 35mm doesn't matter any more. The digital age we live in is blowing all the old standards away like winter leaves on a tree in the autumn breeze. It's kinda sad.
 
commanderspike said:
Isn't the sensor on the GH1 a native 16x9 chip?
Click to expand...
No, it's actually 4:3. Hence the dual nature of the name: it's a 4:3 chip that's 4/3" in size. But it only uses 4:3 in still mode, it uses a 16:9 extraction in video mode (which is actually wider than the 4/3 standard; the GH1's chip is a little oversized in comparison to a regular 4/3 camera).
 
PappasArts said:
Glenn I forgot to ask, curiousn, what 35mm stock # is this?
Click to expand...

I believe the film stock was 5218 Eastmancolor "Vision 2" asa 500.

Please note that I didn't start this thread to get into a film discussion, but to relate the depth-of-field characteristics of the GH-1 to a typical 35mm movie scene. It's obvious from this forum that most people shoot video with a DSLR to achieve film-like DOP and are obsessed with achieving near "night-vision" ISO capabilities.

With the right lens and camera settings, the GH-1 can achieve footage that looks very similar to 35mm that's been transferred to video.
 
BUMPING because of other people's confusion about "crop factor" stuff on the release of the new AF-100.

This is the best, most concise "film vs digital formats for dummies" explanation I've seen of the concept yet, and IMO this should be stickied and moved to the AF-100 forum. :-)
 
sam rides a mtb said:
if im not mistaken, in regards to the acadamy 35mm 4x3 frame, arent anamorphic lenses commonly used so to still utilize the entire frame - not just letterbox it to arrive at the 1.85:1 ratio?
Click to expand...
Anamorphic cinematography is done using the full height, but not the full width, of the 35mm still frame. So you end up with 22x18, for about a 1.2:1 aspect ratio. Since anamorphic lenses use a 2x squeeze factor, this "squeezed" image will be unsqueezed upon projection into the 2.4:1 frame.
 
Semi related aside:

I have a half frame SLR (PEN FT) which has to basically fill a S35 frame size. In fact, people used to adapt their cine lenses to PEN F to use the SLRs as finders for filmmaking and to take pictures for location scouting/storyboarding type purposes (if you hold a PEN F "portrait" style it takes "landscape" style photos.) I have a couple lenses for it an adaptor to put them on the GH1, which works great because the image circle is just a liiiiitttle bit bigger than the GH1 needs (I assume something like that 1.18x number.) I love shooting with the half-frame film camera because it's basically the film progenitor of micro 4/3rds (hence the Olympus PEN m4/3rds cameras.) Similar advantages, including really tiny, really light lenses, and, for better or for worse, a crop factor vs full frame photography film, allowing me to get closer to distant subjects, etc. It also lets me use my GH1 to visualize the film photos before I take them (if I want) which I usually do when using it as a meter (as my PEN FTs meter is dead.)
 
You must log in or register to reply here.
Back
Top