Reservations to close...

Tim Le said:
Actually this does sound plausible. It would be cool too. Imagine shooting a wide shot of the Serengeti on the 18-85mm at S35 scaled to 2K, then when you spot a cheetah going on the hunt, switch to 2k windowed and presto you have a multiplier on your lens and 120 fps to boot!
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Crafty thinking, gents. And yes this would work this way (presuming my understanding of RED's modes is correct). Scaled 2K/1080p would give you S35 DOF and S35 FOV; windowed 2K would give you 16mm DOF and 16mm FOV so yes it would act like a telephoto magnification.

I've been doing this on the HVX, using it in 1080 mode and scaling to SD, and then for ultratelephoto using a "windowed" 1080 mode (that's what I did with the caterpillar video I just posted) and it does work quite well. It'd be more advanced with RED because you'd actually see the effect of the extracted window during shooting.

And 18-85 (or, "virtual 18-170") is all the lens you'd need in many (most?) shooting circumstances if you're okay with swapping between windowed and scaled mode.
 
The question here is going to be how well 2K scaled cuts together with 2K windowed. The scaled footage will probably look a fair bit sharper.
 
Yes, scaled should look better, but depending on the display format, intercutting scaled and native 2K may not be perceptible to viewers. If it's going to TV you can get away with murder.
 
it will be a good test Chris.. if you use cheap lenses that are soft as they roll away from the center of the glass, then you actually gain some sharpness shooting windowed... but most people may never notice the difference, remember 2k delivery is pretty much limited to computer monitors and theaters.
 
Damn!!! I just had the exact same discussion with Greg over here:

http://www.dvinfo.net/conf/showthread.php?t=75585

Only I was a full hour behind you guys. Just when you think your being original! Besides I was never able to say it as concisely as this:

"Scaled 2K/1080p would give you S35 DOF and S35 FOV; windowed 2K would give you 16mm DOF and 16mm FOV"

Serves me right for cruising by dvinfo first. Ha!
 
Right, Tim, the DOF stays the same, while the FOV decreases. You could get the same result by cropping a 2K rectangle out of 4K footage in post.
 
Tim Le said:
I'm not sure if this is true if you are using the same S35 lens and are switching on-the-fly scaled full frame 2K to windowed 2K. You would get 16mm FOV but wouldn't the DOF stay the same regardless of whether you are shooting S35 or S16 windowed

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Yes the DOF would stay the same, the exact same - that's the problem. Traditionally when you switch to a tighter angle, the background becomes softer - but not in this case. If I were shooting on the Red 300mm and switched from 2K scaled to 2K windowed, I would say "wow looks like a 650mm" - except for the DOF.

This is almost an issue of semantics. I think the DOF of the lens would 'numerically' remain the same for hyper-focal distance calculations - but the 'optical' DOF of 2K scaled would not mimic that of truly longer lens. Just because you are jumping into to the center of that lens / sensor to shoot 2k windowed does not mean the background will become softer. This is how Greg put it on that other forum:

"The DOF characteristics of any lens stay the same no matter the format. The DOF of a 300mm lens is the same on a 4K sensor, a 2K sensor, 2/3" or 1/3"... And the blowup analogy works."

BTW here's another tres-valuable Lowry-ism from that thread:

"In case anybody is interested, the RED 18-85mm would be the equivalent of a 38.8-183.5 on an S16 2K windowed sensor. Definitely not a replacement for a purpose-built S16 format lens."
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Would the Cooke 18 to 100mm be a good comparison to the Red 18 to 85mm lense? On the Cooke website it says it's precursor (20 to 100mm) was used along with 25-250mm zoom lenses to film Band of Brothers, which gives an idea of the quality available for TV work, I dare say a whole bunch of the films shot using cooke lenses have used it but it specifically notes this miniseries.

Link to lense on Cooke site
 
For clarification: if you set up a shot and swapped between windowed and scaled, then yes the DOF would stay the same, only the FOV would change.

What I meant by "with windowed you get 16mm DOF and 16mm FOV" is this: if you establish a certain composition in windowed mode, it would exhibit the same DOF properties as a 16mm camera. If you established the same composition in scaled mode, it would exhibit the same DOF properties as a 35mm camera. But you'd have to move the camera closer (or zoom in more) in scaled mode in order to get the same composition.

So -- changing from windowed to scaled will not magically make shallower or deeper DOF -- at the same distance to subject and same focal length, DOF will be identical. But if you're using the camera in windowed mode, as a practical matter you'll be getting 16mm FOV, which means 16mm DOF. If you swap to scaled mode, as a practical matter you'll be getting 35mm FOV, which means you'll have to use correspondingly more telephoto to get an equivalent composition and by doing so you'll get shallower DOF.
 
Hmm, you may be right. I'm having a hard time visualizing it for some reason, but if one is using a lens built for S35 and cropping it... it should maintain all of the same characteristics of S35.

It'd be like taking a shot using a full-frame SLR and then cropping the image in post. The DOF doesn't magically change in the cropping process.

So, yes, I imagine that the DOF would be retained using this lens. If one switched over to a S16 lens, then the S16 DOF would be achieved.
 
I think we're all saying the same thing, just a different way. The "cropping in post" analogy helps a lot. The scene now appears to have been shot on a tighter lens, but without the shallower DOF that a tighter lens would offer. I think (think???? a bit unsure) that a 20mm S35 lens and a 20mm S16 lens would produce very similar 2K digital images (FOV & DOF) when shooting in 2K windowed mode. At least that's what my director's viewfinder tells me. Not sure.
 
So -- changing from windowed to scaled will not magically make shallower or deeper DOF -- at the same distance to subject and same focal length, DOF will be identical. But if you're using the camera in windowed mode, as a practical matter you'll be getting 16mm FOV, which means 16mm DOF. If you swap to scaled mode, as a practical matter you'll be getting 35mm FOV, which means you'll have to use correspondingly more telephoto to get an equivalent composition and by doing so you'll get shallower DOF.
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Thanks Barry i thought all this studying of DOF had went astray for a minute. Maybe we get all this confusion because a simple comment like all things being equal is NOT taken into acount. The real world (which i know nothing about) scenario means that all things are not equal (FOV) so to get the exact scene means adjusting to take into account the reduced FOV going from scaled to windowed mode. I think the red website mentions that in windowed mode using s35mm lens you get s16mm DOF but they did not qualify that statement by saying by adjusting the FOV, to back that statement up? Without any statement are those comments not missleading or actually wrong?

Have i got that right......Greg....Steve.....Barry?

Michael
 
mike the beginner said:
Thanks Barry i thought all this studying of DOF had went astray for a minute. Maybe we get all this confusion because a simple comment like all things being equal is NOT taken into acount. The real world (which i know nothing about) scenario means that all things are not equal (FOV) so to get the exact scene means adjusting to take into account the reduced FOV going from scaled to windowed mode. I think the red website mentions that in windowed mode using s35mm lens you get s16mm DOF but they did not qualify that statement by saying by adjusting the FOV, to back that statement up? Without any statement are those comments not missleading or actually wrong?

Have i got that right......Greg....Steve.....Barry?

Michael
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Ok I might have started this thread astray from "reservations to close" to FOV and DOF, but there was some talk about windowed and full s35 so I chimed in.

Say you have a shot framed up in s35 in an interior of a house, and you are at 50mm and you decide you want to shoot an alternate scene at 120 fps because effects are happening and it would be cool to have some really slow motion stuff for the edit. So you switch over to windowed mode to do that. But you want to keep the framing similar. To achieve the same FOV, or framing you would roughly say have to zoom wider to maybe 25mm or so to keep the same height and width of the shot or , FOV (field of view). But you have just deepened the the DOF (depth of field). DOF is always an equation between lens legnth and apeture. Smaller lens length greater depth of field, wider aperture less DOF. But also as in any HD camera as you increase the FPS you take away light. In other words when you go from 60 to 120 FPS you lose a stop of light, which lessens your DOF. If you went from 24 to 120 FPS it would drop your exposure by about 2 1/3 stops, which may compensate for your focal length shift. This is pure physics...
This is why the s35 is so very attractive to film makers especially in drama. Shallow focus.

Field of View is determined by your format size.

DOF does not care about your format, strictly lens length and iris size, and your iris is influenced by your frame rate when taking about high speed. DOF is format agnositic, period. You change your framing when you change formats and then you zoom wider to compensate, and your DOF increases.

Lenses all throw a circle onto a focal plane and how much of that area we use in a rectangle is the format size. The attributes of that circle does not change as we change formats but we tend to change lens lengths to compensate for the new format and thus change the physics of the image.

This is why I find it difficult to compare still 35mm to anything. Leica cameras were the first 35mm still cameras, and they came about to shoot tests for cine cameras. But they used the film horizontally instead of vertical and we have that same comparison going on now. Is it 18mm or 85mm in still full frame, or motion s35, and what and what does that mean in s16? Actually all 35mm film went through the camera vertically and we got used to ultra wide images horizontally as a by-product of motion picture quality control!

You just have to use the millimeters and then figure out the aperture and the shutter speed and that gives you your DOF. Your lens length times the expousure.

So if you want the same DOF you slap on some Nuetral Density filters and open up from f5.6 to 2.8 to keep the same DOF or allow for the fps or some such scenario. Or you are changing your film speed, i.e. gain. This is why assitant cameramen have DOF and FOV calculators, they also take into account film speed, f-stop, aperture, ISO, shutter, all of these things affect expousre and DOF.

BUT... We have never before been given an option to change our formats on the same camera mid-scene or mid-roll to achieve creative alternatives. So we are thinking about things that have never come up before, really never before on the same camera on the same shoot you just can't change formats on any other camera I can think of!

Pretty cool isn't it? I have never heard of a situation where a camera crew on a show switched from 35 to 16 with the flick of a switch! It is sort of a new mental puzzle to solve.

Mostly people that want to shoot windowed will shoot windowed most of the time. Sports shooters already are shooting in 16mm and love high FPS. They love slow motion, like the people doing snow sports, and motocross and drag racing etc. I have seen a lot of top notch guys on the slopes shooting with A-Minimas. The smaller 16mm lenses are great for handheld work and the high speed is way cool. Also if you are using 35mm zooms you have that much greater telephoto in s16! Also shallow DOF is not very important in high speed work as your exposure needs increase as you go faster so usually you need all the DOF you can get, especially when pulling your own focus.

We are just not used to having so many choices! So as a former film Assistant Cameraman and as a DP on film and video for the last 20+ years I thought I would throw my 2 cents in on this discussion and see if it helped at all.

Brian Ferguson
briferg
Red reservation #12
 
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Pretty cool isn't it? I have never heard of a situation where a camera crew on a show switched from 35 to 16 with the flick of a switch! It is sort of a new mental puzzle to solve.

Mostly people that want to shoot windowed will shoot windowed most of the time. Sports shooters already are shooting in 16mm and love high FPS. They love slow motion, like the people doing snow sports, and motocross and drag racing etc. I have seen a lot of top notch guys on the slopes shooting with A-Minimas. The smaller 16mm lenses are great for handheld work and the high speed is way cool. Also if you are using 35mm zooms you have that much greater telephoto in s16! Also shallow DOF is not very important in high speed work as your exposure needs increase as you go faster so usually you need all the DOF you can get, especially when pulling your own focus.
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That was nice Brian theres more than a few out here that appreciate your post. It is pretty cool aint it, so too in being able to use different mounts.
The latitude that appears to be available, the workflow issues, a waveform monitor with proper HD resolution. its no wonder we all want the camera and hope it fits in with our type of work. I can look at the camera now view its strengths and weaknesses and try to work round the weaknesses. For some people some parts of the cameras strength might well be others weaknesses.

When you look around at this price point of red there is really not much choice like for like is there? I am beginning to realise that it all comes down to whether the format can work for you and be justified in price to do what you want the camera to do. I have reached the point now that there is sufficient advice (thanks guys) out here on this forum to enable everyone to establish if red is a suitable camera for your needs. If others are still windering it will be because they have not spent the time reading enough threads on this red forum.

Chris Kenny just posted a good explanation of DOF when using the s35mm format. Both posts explain real world use without trying to just be smart and knowledgable. No inference meant or intended just real world examples.

I think people understand better when things get explained that way. I am at book number 14 now, 11 of them i could have probably done without. This forum provides better advice and guidance:dankk2:
 
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