MEDIUM FORMAT, help me out Tom

[Pietro Impagliazzo]

Of course many of us here would prefer a much larger format. My guess is that Jim is planning something radically different from modern "full frame" DSLRs.

I think the 15/65mm format would be perfect!!!! Jim??

The main thing I am interested in is advanced exposure control. For instance, I would like to see a "ratchet" timelapse feature that controls exposures through very small-increment shutter speed adjustments (thousandths of a second), but can only lengthen or shorten exposures in one direction. In other words, the "ratchet" feature would be similar to the "click-click-click" on a rollercoaster when you going up the incline. The rollercoaster can go up, but never back. Why is this important? The "Holy Grail" of timelapse is the ability to shoot day-into-night shots, or night-into-day on fully auto exposure settings (in-camera matrix metering, for example). But modern DSLRs do not view an image sequence as a video that needs stable, smooth transitions -- they view each frame as a still. So exposure times jump all over the place as cars or clouds pass through frames. The "ratchet" feature would know in advance that it is trying to make an HD video with very smooth exposure transitions. So, for example, you could be shooting in the middle of the desert with 1/2000th daylight exposures, which would very gradually transition through dusk (1s exposures) all the way to wide open Milky Way night shooting with exposure times of, say, 45 seconds. Not even the great masters like Ron Fricke have truly been able to pull off shots like that!

Regarding exposure times: if it can do 30s exposures, there is no reason it cannot do 90s or 150s. If you are using medium format lenses, you will need longer exposure times than you would with Canon EF bodies.

RED should seriously consider this.

 

[Kyle Presley]

You might think you're getting less total light, but you're not: it's the same. Here's why: at f/3.0, the intensity per-area of light is lower. But there is more total area. So in the end it comes out equal. Why is that? Like with many things, it all comes back to aperture. 50mm/2.0 = 25mm. 75mm/3.0 = 25mm.

Are you sure about this? When I shoot medium format, I use the same metering for my Nikon SLR's as I do my Bronica. I compared the iris diameter of my medium format lenses to my Nikon lenses at various stops and the medium format lens's iris is physically wider than the corresponding stops on the SLR. Of course, I'm comparing apples to oranges though: the MF lens is a 75mm and my Nikon is 50mm, however they are about equal in terms of field of view. My point is, because of the larger field of view of medium format, you will always have shallower depth of field for an equivalent focal length. If you do stop down to get the equivalent DoF, there IS less light. You will have to change shutter speed to get the equivalent photos from both formats.

50mm/2.0 = 25mm. 75mm/3.0 = 25mm.

Maybe I'm wrong about this, but I think that holds true for lenses with the same flange depth, but medium format lenses have a longer flange depth, so less light DOES reach the film plane, that explains why the diameter of the MF irises is larger than the equivalent nikons'.

 

[Daniel Browning]

Aperture fever.

Aperture fever.

Thank you for the discussion, Kyle. I hope that you will find my post informative and helpful.

Are you sure about this? When I shoot medium format, I use the same metering for my Nikon SLR's as I do my Bronica.

Right.

I compared the iris diameter of my medium format lenses to my Nikon lenses at various stops and the medium format lens's iris is physically wider than the corresponding stops on the SLR. Of course, I'm comparing apples to oranges though: the MF lens is a 75mm and my Nikon is 50mm, however they are about equal in terms of field of view.

Also correct. 75mm @ f/2 = 37mm. 50mm at f/2 = 25mm. The 75mm lens has about 50% more aperture at the same f number.

My point is, because of the larger field of view of medium format, you will always have shallower depth of field for an equivalent focal length.

That's not actually true. There are only two things that affect depth of field: the aperture (mm, not f number) and focus distance. Nothing else. Not field of view or film/sensor size. Here's why.

For a given perspective (subject distance), a larger format requires a longer focal length to get the same field of view. A longer focal length with the same f number will have a wider aperture (in mm), and therefore, a thinner DoF.

Looking at the same focal length on both formats is interesting. If you have the same perspective (distance to subject) and focus distance, then the depth of field will be the exact same. That contradicts what you said above, but we both know why: you were talking about moving closer with the medium format camera to get the same field of view as the 35mm format. Of course, sometimes changing distance is impossible or just ruins the shot, which is why I talk about a fixed perspective and focus distance.

But lets look at what happens when you move closer to get the same field of view. The perspective changes. And the focus distance gets closer. The change in focus distance is what causes the medium format to have thinner depth of field. If you moved closer with the 35mm camera, it would have the same depth of field again as the medium format (but again, it would have a different field of view).

If you do stop down to get the equivalent DoF, there IS less light.

There is half the light intensity per area, but there is double the area. Therefore the *total* amount of light is the same.

You will have to change shutter speed to get the equivalent photos from both formats.

If the technology was equal, then you would get equivalent photos without slowing the shutter speed. Here's why: The MFDB will have the disadvantage of needing a one stop push. The 35mm will have the disadvantage of needing twice as much enlargement for a given print size -- bringing them back to equivalence. If you do slow the shutter speed on the Medium Format, then it will have *more* total light than the 35mm, and will look better at equivalent print sizes. Another way to think of it is if you shrunk the Medium Format negative (or MFDB file) down to 35mm size, the light intensity would go up one stop.

Unfortunately, the technology is not equal. You might be able to try the above experiment with the same film in 35 and MF, but since film has non-linear response, even a one-stop push might skew the comparison. If the scene had low contrast and was exposed to fit entirely within the linear portion of the film response curve, then the experiment would work.

Maybe I'm wrong about this, but I think that holds true for lenses with the same flange depth, but medium format lenses have a longer flange depth, so less light DOES reach the film plane, that explains why the diameter of the MF irises is larger than the equivalent nikons'.

A longer flange depth doesn't mean less light reaches the film plane, it just places constraints on the lens design. Longer depths require more telecentric lens designs, shorter and it bangs into mirrors and causes vignetting (angle of incidence). The more important technical limitation is that MF lenses need to throw a larger image circle than 35mm and have longer focal lengths for the same FOV.

For another illustration of the amount of light and equivalence, consider the following:

Subject distance: 5 feet.
Focus distance: 5 feet.

• APS-C camera, ~425mm^2 sensor/film area, 35mm, f/1.4, 1/250, ISO 100.
• 35mm still camera, ~850mm^2 sensor/film area, 50mm, f/2, 1/250, ISO 200.
• Medium format, ~1700mm^2 sensor/film area, 75mm, f/3, 1/250, ISO 533.

All three of those shots will have the same perspective, field of view, depth of field, and total amount of light. If they had the same linear film or sensor technology and perfectly matched lenses, then the final image would also be the same.

Notice how 35/1.4 = 25, 50/2 = 25, and 75/3 = 25. Again demonstrating that total light gathering ability and depth of field are determined by actual aperture.

 

[Kyle Presley]

Wow, that's a lot of information. Let me digest this. I'm still a little confused as to how all this works if it's metered the same. Let me read through a few more times. Thanks for the reply Daniel.

 

[Kyle Presley]

OK, I get it now. I didn't fully understand the relationship between focal length and f stop as it applies to aperture. Now I think I have a better grasp of this. You're much better at articulating this stuff than I am. I fully concur with what you're saying, I just misunderstood at first. I love this forum, it's full of knowledgeable people, and no consultation fees! Do you mind, Daniel, if I ask what your photography background is?

 

[Daniel Browning]

Do you mind, Daniel, if I ask what your photography background is?

Not at all. I got into photography about two and a half years ago; video shortly after that. My day job is software, but in my spare time I shoot weddings/events, timelapse, astrophotography, macro, and landscapes.

 

[jean_dodge]

What if?

What if this new Red still camera was revolutionary in extending the dynamic range by virtue of using its large sensor to fracture an image into say, quarters - what if the lens used a prism or even a moving sensor somehow (I'm a terrible inventor, don't quote me on this stuff!) to enable multiple exposures within say, 1/1000 of a sec in order to enable handheld shots that became HDR composites?

Some motion picture ultra high speed scientific cameras used a spinning prism to create fast multiple images that filled a normal transporting 35mm film frame with four images per frame, thus quadrupling the effective frame rate at the sacrifice of image size/resolution. With a still life or a cooperative human model, you can already use a DSLR to make an HDR image by employing fast bracketing, at say 5 fps or so and the results are good enough to fool the eye, even when shot handheld.

As mentioned above, for 90% of photojournalism work, and any work for print that is bound into a book or magazine, sensors larger than Super35 size are mostly overkill, as is anything above 24 megapixels unless your job is to make huge enlargements. Red has experience making large sensors - so I'm just thinking about ways in which they might employ this tech to still photography. It seems like HDR, panorama, timelapse and high frame rate are areas in which they might reasonable be expected to deliver surprises or advantages over DSLR companies like nikon, canon et al.

I doubt this is what Red is doing, but it does seem to be within their grasp.

My other guess as to what this "revolutionary" still camera might be would be a possible bridge between MF and 35mm, combining some good aspects of both.

 

[Kyle Presley]

What about a medium format 6x6 sensor with very large pixels? Native HDR without multiple exposures.

 

[Deanan]

That's not actually true. There are only two things that affect depth of field: the aperture (mm, not f number) and focus distance. Nothing else. Not field of view or film/sensor size. Here's why.

Not exactly true. Circle of confusion is the third factor (and images size as an extrapolation).

Additionally, other factors in the system like OLPF, grain, noise, etc affect the sharpness quality and CoC which in turn affect the perceived depth of field. Ultimately, you also have to factor in qualitative assumptions about what the cutoff for in focus and out of focus is.

 

[Daniel Browning]

Not exactly true. Circle of confusion is the third factor.

Oops, forgot about that one. That's one of the neat things about capturing and viewing at 4K: the depth of field is thinner.

 

[Deanan]

Oops, forgot about that one. That's one of the neat things about capturing and viewing at 4K: the depth of field is thinner.

I forgot to mention that the debayer also affects DoF.

To some extent, the scaling algorithm does a little bit also.

 

[Tom Lowe]

Deanan, what do you think about the exposure "ratcheting" idea? It might be a pain to design, but Red's DSLR Killer would be the only camera on the planet with that feature. The resulting shots would really be something, IMO.

 

[Deanan]

Deanan, what do you think about the exposure "ratcheting" idea? It might be a pain to design, but Red's DSLR Killer would be the only camera on the planet with that feature. The resulting shots would really be something, IMO.

I used to do lots of timelapse years ago and I would do similar things with multiple exposures and accumulating the exposures for each frame. it works well and you have the advantage of being able to control things more precisely when you're 'developing' the timelapse in post. However it did require custom tools to blend or select images and laptop to control the camera.

I had a simpler version that just used a light sensor to ramp the iris in one direction.

 

[Tom Lowe]

Yeah, but ramping the IRIS will obviously change your DOF, and it's not enough control to go from a daytime desert, for example, to a moonless desert exposed for the Milky Way. You're talking about going from 1/2000s to like 45s.

 

[Deanan]

Yeah, but ramping the IRIS will obviously change your DOF, and it's not enough control to go from a daytime desert, for example, to a moonless desert exposed for the Milky Way. You're talking about going from 1/2000s to like 45s.

It works ok for some types of shots and is simple to implement. The DOF change can also be a nice addition sometimes.
More complicated shots I had to use external control to change exposure time but this also has limitations.

 

[Tom Lowe]

Yeah. A system that uses internal (through the lens) matrix light metering with uni-directional, small-increment shutter ramping seems like the best solution... at least that I can think of.

 

[Deanan]

Yeah. A system that uses internal (through the lens) matrix light metering with uni-directional, small-increment shutter ramping seems like the best solution... at least that I can think of.

What I used to like to do the most was to do multiple exposures per frame at the same exposure or at multiple exposures (depending on the goal) and then doing weighted averages.

Later I also started to shoot a sample frame, analyze it, and then trigger another frame with the correct exposure.

Unfortunately, I haven't had time to do any timelapse in the last 8 years.

 

[Tom Lowe]

What I used to like to do the most was to do multiple exposures per frame at the same exposure or at multiple exposures (depending on the goal) and then doing weighted averages.

Later I also started to shoot a sample frame, analyze it, and then trigger another frame with the correct exposure.

Unfortunately, I haven't had time to do any timelapse in the last 8 years.

Well, what about automating this with DSMC?

Please.

 

[Nova Invicta]

Complexity vs Simplicity

Complexity vs Simplicity

Most of the points discussed here are complex by comparrison to the Red One which basically removes the complexity to the posting of raw images which is also the reason the camera is cheaper than anything Sony or Panny do. Hasselblad already have a 50MP camera back and Leica have created a halfway format with 37.5MP. The biggest weakness of Red One and most digital cameras is dynamic range if Red is really radical it will find a way of resolving this. Kodak newer bayer filter is a step in this direction and its first application in mobile phones will start to erode the whole digital compact market which will need to move up to full frame 35mm or to keep it small micro 4/3rds type cameras. Likewise DSLRS will need to move up like Leica is doing and Nikon is rumored to be doing to medium format type sensors with dynamic range over MPs being more important.
Once again however the topic is hijacked by the sensor when the "System" is all important also and that includes lenses, accesories & software.

 

[Joseph Ward]

We know that DSMC will have movie mode because Jims dsMc distinct difference of DSLR. If Red were to make a Medium Format DSMC they might as well combine it with Epic. Epic/DSMC