1/4 inch sensors. Even harder to shallow DOF?

[Tim Le]

Originally Posted by Matt Daviss

Is it possible to show comparisons for 1/4", 1/3" and 2/3" rather than/as well as Super35? Many thanks, much appreciated.

Glad to help! I ran the numbers for 2/3" below. I'm not exactly sure what the size of a 16:9 2/3" sensor is so I just used Fujinon's 35mm-to-2/3 16:9 multiplier factor of .254. From that I estimated the circle of confusion to be .0076.

For the heck of it, I also added 1/2" sensor based on Fujinon's 35mm-to-1/2 conversion factor of .178.

Here are the results:

Given:

• FOV: 50mm lens (in 35mm terms)
• Aperture: f/2
• Distance to subject: 5 feet

The DOF would be:

1/4" sensor:

• Actual focal length: 5.2mm
• Circle of Confusion: 0.003
• Near focus distance: 3' 8.9"
• Far focus distance: 7' 6.5"
• Depth of field: 3' 9.6"

1/3" sensor:

• Actual focal length: 6.9mm
• Circle of Confusion: 0.004
• Near focus distance: 3' 11.8"
• Far focus distance: 6' 8.5"
• Depth of field: 2' 8.7"

1/2" sensor:

• Actual focal length: 8.9mm
• Circle of Confusion: 0.005
• Near focus distance: 4' 2.4"
• Far focus distance: 6' 2.2"
• Depth of field: 1' 11.8"

2/3" sensor:

• Actual focal length: 12.7mm
• Circle of Confusion: 0.0076
• Near focus distance: 4' 4.5"
• Far focus distance: 5' 10"
• Depth of field: 1' 5.4"

Super35mm Cine:

• Actual focal length: 34mm
• Circle of Confusion: 0.019
• Near focus distance: 4' 9.2"
• Far focus distance: 5' 3.1"
• Depth of field: 0' 5.9"

If anyone sees any errors, please feel free to correct them.

[Heath McKnight]

It's got a 20x zoom lens, so shallow depth of field isn't too bad at all.

heath

[Bill Pryor]

That's right--if you want an ECU of a person's eyeball and nose, then the depth of field would be pretty shallow.

[Tom Hardwick]

Quite right Bill. Heath - the longer the focal length of the lens the tighter you'll frame, that's all. You must combine this with big gates (chips) to get useful photographic differential focus.

tom.

[Steve Mullen]

Originally Posted by Tom Hardwick

You must combine this with big gates (chips) to get useful photographic differential focus.

With JVC's 30p one had to shoot in a manner appropriate to the frame-rate. With the V1, we will have to learn HOW to shoot with deep DOF.

But, I'll say that for every person who needs minimal DOF there are ten who will be shooting in situations where max DOF will save the shot by keeping good focus.

Minimal DOF is most relevant for those shooting 24p. For every person who shoots 24p, 100 or even a 1000 will be shooting 60i. IMHO, the future is HD at 720p60, 1080i60, and in late 2007 -- 1080p60.

[Tony Tremble]

I am constantly surprised by "filmmakers" shooting video trying to emulate the film medium of Hollywood. Personally I see these cameras a different medium in themselves and see the differences between film and video as positives to be explored rather than negatives to be worked around e.g. with expensive clunky 35mm adaptors. In my view the small, lightweight high quality camera packages are liberating and far outweigh the considerations of shallow depth of field.

Some of the greatest filmmakers and if not the finest of our time, Abbas Kiarostami, regularly use Deep Focus as a device.

...getting back on topic, I thought I read that the 1/4 inch chips were arranged such that their effective area was the same as 1/3 inch CCDs. I'm pretty sure I'm not going mad. Always a possibility though... But if true should mean little or no difference between DOF of previous cameras such as the Z1.

TT

[Bill Pryor]

Welcome to the marketing circle of confusion, Tony. If you haven't read Rushkoff in awhile, it might be a good time to pick up a copy of "Coercion." It's all about corporate control.

Sony does, indeed, say that by rotating the chips they get the same imaging area as with 1/3" chips. And my first thought was the same as yours: If that's true, then the depth of field should be the same too, and a 3.5mm lens should be a really nice wide angle lens. But it isn't and it isn't. That superwide lens, in fact, is very close to 40mm, in real lens terms. So, you're shooting with a 1/4" chip camera. Even Sony can't violate the laws of physics. Maybe the 1/4" CMOS chips provide a picture quality equivalent to 1/3" CCDs, but they're not the same size. There's electronic magic going on there that I could never hope to understand, but 1/4" is still 1/4". I'm not knocking the camera--hell, I might even buy one one of these days.

As far as emulating film look, that may be the reason some people use shallow depth of field. I don't. I use it selectively depending on the shot. For example, I had a shot of different size wine glasses lined up, a very tight shot, filling the frame. I shot wide open, dropping the background a couple of stops, backlighting the glasses and with about a 1 foot depth of field. That popped everything nicely. You can't do that with a 1/4" chip camera, or a 1/3" chip camera for that matter. Shallow depth of field can be very useful. When shooting interviews in public places, I like a shallow depth of field so when people walking by in the background look at the camera, you can't tell what they're doing. You can do that, just barely, with a 1/3" chip camera, but most likely not with 1/4".

I think if a guy wants to use a 1/4" chip camera for serious moviemaking, then he would be very interested in one of the spinning ground glass adapters. Not for everything, but for some shots. Those gadgets wouldn't be all that bad to use if they get the flip thing done. I've read that the Brevis may have a right-side-up model soon. If the V1 turns out to be a successful camera, which it very well might be, then I'd guess the sales of the ground glass adapters would soar. Time to dig through my old still camera bags and see how many pre-AI Nikkor lenses I can come up with....

[Tom Hardwick]

You raise good points about limited DOF Bill, and here's another. Probably the most difficult image to successfully compress to MPEG2 for DVD is a field of waving grass. I've tried it and no way is it as smooth and clean as the original MiniDV master.

So to give DVD players an easier time, have as much of the frame as soft and blurry as you can make it - that way the compression gets used where it's needed, and BCU of faces with out of focus backgrounds and foregrounds look pin sharp and beautifully detailed.

tom.

[Bill Pryor]

True. Also in film-originated shots like that, when a person is running across the frame, the background is usually a little softer, so you don't really notice the strobing if the pan is too fast.

If somebody (like Redrock or Cinevate) would make a 35mm adapter than allows you to shoot right side up, then that would certainly make the V1 a much more desireable camera for low budget movie work. Same for any 1/3" chip camera. Shooting upside down isn't so bad, actually--it would be like using a view camera again.

[Bogdan Tyburczy]

The industry could build more versatile image flip functions in the cameras, not only EVF flip, but also actual image flip. Upside-down issue wouldn't be an issue, but for now, we have to deal with it.

Deep DOF is especially painful in wide shots in SD, when all the background details are in focus or so, but the camera resolves them like some sort of moving pulp. In HD it does not hurt so much. Background detail is resolved in much more pleasant way, but I absolutely don't mind larger sensors :) 1/3" vs 1/4" matters and 35mm adapter is not always handy.

[Phil Bloom]

yeah totally agree.

Such a shame sony went with 1/4 chips. Completely put me off. My Letus35 is great but heavy, cumbersome, fiddly and only for stuff close to me. So if I "running and gunning" I can't get something far away without taking the letus off. Not a simple thing with rods etc..

[Stu Holmes]

Originally Posted by Phil Bloom

Such a shame sony went with 1/4 chips.

I think people's desire for 3CMOS 1/3in. cam stands a good probability of being satisfied within a number of months time. There's always a method to a company's apparent 'madness'..

just an opinion.

[Bogdan Tyburczy]

Hard to say, but it's possible. Sony invested in new technology and will probably wait to gain profit from that before introducing larger version. 1/4" ClearVids sit in FX7 also. Sony's choice of 1/4" size was primarily about cost effectiveness. 1/3" would bump up the price much more above XH-A1 level.

[Tom Hardwick]

I agree. A 1"/4 chip has an area of 8,17 sq mm, whereas the 1"/3 chip has an area getting on for twice that: 14.52 sq mm.

Such a surface area demands a much bigger and heavier lens, as can be witnessed by comparing the TRV900's 12x zoom with that of the 12x zoom fitted to the VX2000.

tom.

[Heath McKnight]

Don't forget, it has a 20x lens so getting the shallow DOF isn't hard.

heath