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Getting the smallest deep of field


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#1 Arnaud M. St Martin de Veyran

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Posted 18 August 2005 - 04:51 PM

Hi Guys !

I've a question, maybe stupid.

Do you think that shooting with HD lenses on a SDX900 are going to give a kind of smallest dept of field that with a 35mm lense adaptor ?
What about the light quality lost ?

I've to say that after i planning to blow it to 35mm.

Hope to heard from you.

Thanks in advance.
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#2 John Ealer

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Posted 18 August 2005 - 05:06 PM

Assuming the aperture is set the same on both the film and HD lenses, film lenses attached to the P+S Technik adaptor will have less depth of field than the HD Lenses, simply because the HD CCD is smaller than the 35mm-sized ground glass in the adaptor.

Obviously, much depends on what kind of PL mount lenses you use on the adaptor, and what kind of HD glass you're using. Personally, I would prefer to use Zeiss Digiprimes wide open at T 1.3 than use Cooke S4's on the adaptor wide open at T2.0 (effectively around a T4 from an exposure - not depth of field - standpoint, due to the light loss through the adaptor.)

J
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#3 Arnaud M. St Martin de Veyran

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Posted 19 August 2005 - 02:35 AM

Thanks a lot.

So you're saying that going HD lenses directly on SDX900 will be better in image quality than with the P+S technik adaptor, right ?

I understand that with the adaptor i'm getting a fake small dept of field but i'm also loosing quality. I'm just scared that with HD lenses i'm just gonna ended with a regular video dept of field and that's really disturbing.

Again, shoot with HD lenses will offer a really good optical quality but still a very wide dept of field ? I would like to get closer as much as i can to an 35mm dept of field to be able to play with foreground and background in focus or not.
Any thaughts ?

Have a nice day.
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#4 John Ealer

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Posted 19 August 2005 - 12:15 PM

Thanks a lot.

So you're saying that going HD lenses directly on SDX900 will be better in image quality than with the P+S technik adaptor, right ?

I understand that with the adaptor i'm getting a fake small dept of field but i'm also loosing quality. I'm just scared that with HD lenses i'm just gonna ended with a regular video dept of field and that's really disturbing.

Again, shoot with HD lenses will offer a really good optical quality but still a very wide dept of field ? I would like to get closer as much as i can to an 35mm dept of field to be able to play with foreground and background in focus or not.
Any thaughts ?

Have a nice day.

<{POST_SNAPBACK}>


Unless you're referring to objective benchmarks like MTF (Modulation transfer function) or signal to noise ratio, the term "image quality" is notoriously subjective. Putting HD lenses on the SDX-900 will, in my opinion and to my tastes, yield an image that looks better for most applications than that achieved with P+S Technik adaptor.

Because the SDX-900 is a standard def camera that uses around 3:1 M-JPEG compression to get a 50mb/s data rate, I think adding the "softening" effect of the ground glass in the adaptor takes too much crispness away. (If you're shooting HD, the softening effect of the adaptor might be more desirable.)

More specifically about depth of field, here's a rough example assuming you're shooting the 1.85 aspect ratio. (For the purposes of this comparison, I'm using a "standard" 25.4 micron circle of confusion for the 35mm primes and a "standard" 10.1 micron COC for the HD lenses.)

If you use a 40mm Zeiss Digiprime at T1.6 on the SDX-900 to do a close up on a subject 8' away, you'll have around 5" of DOF.

If you use the P+S Technik adaptor with an 85mm film prime lens at T2 (which will give you the same image size as the 40mm Digiprime), then you have around 3" of DOF.

A 14mm Digiprime at T1.6 will have about 3.5' of DOF at 8'.
A 28mm (35mm film) prime at T2.0 will have about 2'2" DOF at 8'.

My point is basically that if you shoot with Digiprimes wide open (which are super clean and sharp, even wide open), you're not going to get the "regular video" depth of field look. Yes, you will have less DOF with the P+S Technik adaptor, but you have to weigh that against the "cons" of the system, which are light loss through the adaptor and the increased complexity of the system.

Your best bet is, as always, to try some tests and see what you like better. You can get excellent results with either system. Neither alternative is particularly cheap.

J
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#5 Arnaud M. St Martin de Veyran

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Posted 21 August 2005 - 03:29 AM

Thanks again !

I really got the answer i needed ;-)

I knew that the image quality is a very subjective point so i was just wondering a point of view. Thanks for yours. It match with my theory.

I expected that with P+S Technik adaptor i'll lost some quality so i was already thinking to for HD primes. The examples you gave to me show me how the dept of field is already small, in a way.

The only thing is i'm not going to get Digi Primes but Fujinon HD lens style cause of the budget. Any point of view or advice about the Fujinon ?

Also, i'm wondering what is the lense equivalent between 35mm and SDX900 ?
I mean, if i want the same frame as a 50mm in 35mm format which HD lense is going to be ?

Then, i'm looking for a good monitor to see what i'm doing.
I'm thinking to get a 14" monitor but what does that mean SDI ? Standard Interlaced ?

If you have any advice again, let me know...

Have a nice week end.
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#6 Phil Rhodes

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Posted 21 August 2005 - 07:53 AM

Hi,

I don't understand what all the fuss is about. My fairly cheap, very basic Fuji S20x6.4 lens has a stop below 1.3 which it just calls "open" and this is typical of video lenses - you want less depth of field than that?! That's like shooting 35mm at a T4. Are apertures smaller than T4 considered unusable on 35mm shoots these days?

On the other hand, whatever guild there is that supports focus pullers must be cackling with glee...

Phil
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#7 John Ealer

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Posted 21 August 2005 - 10:23 AM

Hi,

I don't understand what all the fuss is about. My fairly cheap, very basic Fuji S20x6.4 lens has a stop below 1.3 which it just calls "open" and this is typical of video lenses - you want less depth of field than that?! That's like shooting 35mm at a T4. Are apertures smaller than T4 considered unusable on 35mm shoots these days?

On the other hand, whatever guild there is that supports focus pullers must be cackling with glee...

Phil

<{POST_SNAPBACK}>


Phil -

The sharpness difference between a Fujinon S-series zoom wide open and a Zeiss Digiprime is going to be pretty remarkable. Also, if you're shooting with an S-series lens that means you had a 1/2" sensor camera, which will have inherently more DOF.

Your point is well made, however - a 2/3" sensor in a video camera is very close to the size of a 16mm film frame. So depth of field characteristics between 16mm and HD or SD are very similar. Not as shallow as 35mm, but if treated properly, can yield very appealing results.

J
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#8 John Ealer

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Posted 21 August 2005 - 10:31 AM

Thanks again !

I really got the answer i needed ;-)

I knew that the image quality is a very subjective point so i was just wondering a point of view. Thanks for yours. It match with my theory.

I expected that with P+S Technik adaptor i'll lost some quality so i was already thinking to for HD primes. The examples you gave to me show me how the dept of field is already small, in a way.

The only thing is i'm not going to get Digi Primes but Fujinon HD lens style cause of the budget. Any point of view or advice about the Fujinon ?

Also, i'm wondering what is the lense equivalent between 35mm and SDX900 ?
I mean, if i want the same frame as a 50mm in 35mm format which HD lense is going to be ?

Then, i'm looking for a good monitor to see what i'm doing.
I'm thinking to get a 14" monitor but what does that mean SDI ? Standard Interlaced ?

If you have any advice again, let me know...

Have a nice week end.

<{POST_SNAPBACK}>



Fujinon glass should be great. Don't know it as well as I haven't used it as much. An SD lens will need to have a focal length of just less than half of a 35mm lens to have the same field of view as that 35mm lens.

What monitor you want will depend on your shooting environment. If you're out in a cow pasture, you probably won't want to be lugging around that 14"-er. If you're in studio, however...In general, I've had good luck with the Sony HR (high res) monitors.

SDI (serial digital) is ideal but not essential - youll need to make sure the SDX-900 you have has the SDI board installed. At the very least, make sure you get a monitor will 400 or more TV lines resolution. The Sony HR monitors work nicely, a good 9" unit is the PVM-9L3.

J
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#9 Stephen Williams

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Posted 21 August 2005 - 10:42 AM

That's like shooting 35mm at a T4. Are apertures smaller than T4 considered unusable on 35mm shoots these days?


Phil

<{POST_SNAPBACK}>



Phil,

It depends on the look you want! With lenses like the Cooke S4 they are pin sharp at T2 and the new Master Primes are pin sharp at T1.4. I shoot 90% of my 35mm work between T2 and T4.

Stephen
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Media Blackout - Custom Cables and AKS

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