Depth of field is a function of lens focal length, aperture and diameter of the Circle of Confusion (Cc). The Cc represents the diameter of an out-of-focus image of a point of light that we perceive as being "in focus". The smaller the viewed image the larger Cc needs to be before we observe "not focussed". Similarly the larger the "negative" the larger can be the Cc for the viewed image size. So the Cc is related to the magnification of the viewed image. For cinema projection of 35mm film the generally accepted Cc diameter is 0.025mm, and for 16mm it is 0.015mm. It will be smaller for a 1/3 inch CCD and will depend on the viewing setup (monitor or projection).
So for all video cameras with 1/3 inch CCDs with lens of same set focal length and same aperture, the depth of field is the same. Whether zoom or prime, doesn't matter.
DOF calculations are based on the hyperfocal distance H (when focussed at the H everything is perceived as in focus from half the H to infinity),
H= F*F/(f*Cc), where F = focal length, f=f/stop

so then for any focussed distance S:
DN= H*S/(H+(S-F)) -- near limit
DF= H*S/(H-(S-F)) -- far limit

DOF = DF-DN

So given you know the DOF you want, you can calculate the focal length and aperture you need to use. If you want shallow DOF, you'll work at maximum usable aperture (many lenses have maximum resolution at smaller than max aperture) and the longest focal length that suits the perspective of the shot. Remember also that all optics are limited by diffraction (maximum resolution depends on aperture), so short focal length lenses (such as those on 1/3 inch CCD cameras) suffer significantly from diffraction softening of the image for apertures >f/5.

Perhaps you should have a look at the M2 cinema lens adapter.

Looks as if the M2 is the same as the micro35? I thinkk this attached to a Z1 is the way we're going to go...

Yes, the same as the Micro35 -- name revised. Cineform has option to invert the image from the M2 during capture, which is necessary.

Jessariah, I've got two of the M2's, one we bought when they first came out, and one of the more recent builds. They are awesome. Cheno shot some really sweet footage with it recently, maybe he can give you some pointers.
BTW, We're giving one of these away on the HDV tour...Fly to Florida or Burbank, maybe you'll win!

For about the same money as the extra lenses and a spinning piece of frosted glass why not buy a camera with 2/3" CCDs? That'll give you better latitude, around the same DOF and way less noise.

I'm curious, has anyone done any resolution tests using the M2?
I've raised this question several times in various places and when pushed their advocates all admit that image resolution suffers, all they seem to keep ranting about is the DOF and how they can put expensive hunks of the best glass man can make in front of a prosummer camera, sorry but the whole logic of the exercise escapes me, it's akin to buying a $20K mod kit that lets me put a Porche engine in a VW.
Bob.

Bob, the M2 is $695.00 USD, plus maybe $200.00 for a 130mm lens. The resolution does take a hit due to the ground glass, but it's quite sharp nonetheless. It's more than just DOF, it's the overall look. It's a nice appearance, even though it's a poor man's higher end gig. If the M2 was nearly 10K like the P+S is, then I'd agree with you.

Picture is obviously important (and I suspect that HDV with a Z1 out of the box will beat the look of my last feature, which was shot on a GL2...)

I don't mind the resolution taking a hit - so long as it's focusable. Personally, I prefer the "less-sharp" look.

After storyboarding this, I realize that there is a lot of close up framing, which will help to "enhance" the DOF. To me, the medium shots are really what get you. You expect to see much in focus when shooting wide and backgrounds out of focus when in close, but the medium shots are what tend to tip the hand, and I just don't think 54mm is gonna cut it in that respect (considering I'm used to 84mm and THAT didn't always get it done).

Thanks for the input.

K

I haven't tested the M2. When I first read about it I thought this must be the equivalent of magnets on fuel lines to give better petrol economy. But it seems to have a certain amount of respect from people I respect so I'm not commenting until I see results. I've been offered a try, so I guess I should take it up. However knowing that a lot of 35mm cinematography is done with short focal length lenses for intimacy, I rather expected people to be using 20mm focal lengths rather than 130mm.

Oops,
my apologies, I twas indeed confusing it with the P+S mini35, if it was the mini35 you were giving away I think I'd flying to the USA just have a chance at winning one, given what they're worth.
Bob.

Serena,

I'm confused. How would a 20mm lens be more intimate? That's pretty wide / inclusive, isn't it? Whereas a 130mm would make it much easier to isolate a subject from the background and foreground. Maybe I misunderstood what you meant?

I'm not Sarena but I'll add an observation if I may, longer lenses compress depth. Just watch a wildlife doco, you'll oftenly feel that Attenborough is only feet away from the lion when in fact he's 100s of feet in front of it, the effect overall is that we feel like a distant observer which we are because the camera is so far away from the subject even though the subject is full frame. What's also being altered is perspective. If you've got a long zoom and an equally long dolly you can pull a neat optic effect by pushing in while zooming out so that all that shifts is perspective.
I suspect it's just this (the perspective issue) that makes using a long lens to get limited DOF not as effective as using a wide lens with the same DOF, the wider shot even though framed the same puts us closer, sort of we're in the room not peering in from outside if that makes any sense.
Bob.

Yeah, that makes sense. I'm literally talking about "camera on a person and something 20-feet behind him is blurred." I know to get this effect, I move the camera back and zoom in. If I zoom out and move the camera closer, I can have the subject be the exact same size in the frame, but the background is more in focus. From what I understand, I have "more" ability to do that with a 20X lens that goes to 108mm as opposed to a 12x lens that goes to 54mm.

Maybe my definition of DOF is not accurate / what I'm talking about aesthetically. I'm just trying to avoid having a medium shot of someone and EVERYTHING in the distant background in clear focus.

In my DP opinion there are TONS of better choices to work with. For the amount of money you have ($10,000) you can rent CineAlta and get real HD. Or remain SD with DVCPro of SDX900 -- less res then Z1 but hell better quality. Closeups and Mediums will look good with any camera it's with med-wides and wides where the gear you are using comes into play. Honestly i would still choose DVX100 or XL2 over Z1. Again my opinion based on lots of experiences with above gear and 2 encounters with Z1.

I'm just trying to avoid having a medium shot of someone and EVERYTHING in the distant background in clear focus.

If it's at all possible (i.e. controlled situation), my suggestion is run the camera's iris wide open. I did an interview some time back that had a table full of presents (my preferred background instead of a blank wall) no more than 3 ft. (1 m.) behind the subject. I did not want the presents to distract from the interviewee so I opened the iris to maximum and then lit the subject and presents separately. I was fortunate in that I showed up early for this and had a lot of time to experiment. It paid off though as the background was far enough out of focus to satisfy me.

Mike

Patryk -

I'm with you 110% - if I had my way, I'd break out an XL2 and go...but all we hear on the rep/distribution end is "hi-def," so that's "almost" an imperative. And the $10K isn't really the budget - I'm pulling in some of my own money for this, so if I go that high, I need to "own something" when all is said and done.

My wife actually suggested I just worry about making a good movie and consult with my DP on the camera stuff...right after I join control-freaks anonymous...

This has been an interesting thread. Thanks to all for the input.

Kevin

Great thread.

I can achieve some amazing shallow DoF using the Iris-wide method. To compensate for the over-exposure, I employ a variety of NDs ( neutral density filters ) - these range from a mixture of 0.3 up to 0.9 solids. Used in conjunction with my on-board 0.9 ND I can achieve 2.4 ND!

Oh, did I say I use a Canon XM2 SD?

Grazie

Actually the camera doesn't matter at all, as Serena explained it's purely a function of optics, good glass or bad glass, VHS or 35mm or IMAX the same laws of physics apply.
Anyone tried using split field lenses with video, nice way to get some interesting FXs that today will have everyone thinking you spent a fortune on CGI. Optical FXs have sort of gone out of vogue which might be a pity as they're pretty cheap to do and you don't needs a few 100 gigaflop CPUs to do them.
Bob.

Bob? Your, "Actually the camera doesn't matter at all, .. . " was, I guess, your positive feedback to my feeble attempt to suggest by my "Oh, did I say I use a Canon XM2 SD?" comment? No?

G

Yes :)
Sorry just a bit punch drunk from hanging around in another forum, NOT a Canon one though, that's for sure, at least Canon users always seem pretty objective.
You'll be pleased to know it looks like we'll be buying our first Canon cameras in five years, the XL H1 is looking VERY promising, hope it hangs out well with Vegas.
Bob.

Grazie,

As I stated above, SD vs. HDV is not my choice. I'm a Canon fanatic, so the XL2 would be my first choice. But when my producer says that "everyone out there wants hi-def if it's a digital project," it forces me to go away from SD.

As tough and subjective as the industry is, anything I can do that wil help sell the finished product I will do. In this case, the format is the first thing they want to know about - many times before genre or named talent involved. Whether HDV is overrated or not is not an issue. Whether you can get a great-looking finish out of a SD camera is not an issue. If your answer to their first question - Did you shoot it in hi-def? - is "yes," you have an automatic edge.

So, what do I do? Ultimately, this is a business. Period. You'd like to think it's more creative than it is, but it isn't. If they want hi-def, that's what they get. So I come to the people here and the great folks at VASST, get some help & feedback and move on.