depth of field wit ultra primes&416

[christian hennermann]

hi there,

we r shooting with ultra primes and the arri 416. now, is the depth of field the same even though i'm using 35mm lenses on a super 16mm? or is it still what it would be like with a16mm lens like the zeiss high speeds..?

 

example:we r shooting with the UP50mm and the arri416. is the depth of field now like a 50mm on 35mm camera or rather like a 65mm on a 16mm camera?

[Patrick Neary]

hi-

 

you should be using the depth of field tables for 16mm, for the 50mm. The lens stays the same, but because 16mm and 35mm have different circles of confusion (.001" for 35 and .0006" for 16) your DOF will be different for each format (slightly less forgiving in 16mm).

[Larry Nielsen]

This is one of these questions that always sparks debate, Doug Hart and myself have tried over and over and over again to explain this one, and I have to laugh because to this day I don't think anyone will ever get it unless Doug decides to specify a chapter in his book about this. Depth of field is based on focal length, distance to subject, and t-stop. Where the confusion comes in, is in the format, 16mm vs. 35mm. The confusion now is whats considered the field of view. For practical purposes, lets say 16mm is half of 35mm, I know its not, but if you follow along you may get a better picture of where I'm going. Lets say I have two cameras side by side, one a 416, and the other an Arricam Lt. I put a 50mm prime on the Lt, and at 5' I've filled the entire frame with a slate. Now I take that same lense and I place it on the 416, in order for my slate to fill the entire frame, I now have to take the slate out 10' Why? Because if 16mm was half of 35mm, which its not, my 50mm prime is now equivalent to a 100mm prime. So now heres the question. Which has greater depth of field, the 50mm on the Lt at 5' with a T.4, or a 50mm on 416 at 10' with a T.4? Now knowing that, is depth greater in the 16mm format? I don't know about you, but I'd rather be pulling focus on a 50mm at 10' versus 5'. That should help you.

Larry

[Stephen Williams]

[quote name='Larry Nielsen' post='189535' date='Aug 24 2007, 09:24 AM']Depth of field is based on focal length, distance to subject, and t-stop.

Now knowing that, is depth greater in the 16mm format? I don't know about you, but I'd rather be pulling focus on a 50mm at 10' versus 5

Larry[/quote]

Hi Larry,

DOF is connected to the 'F' stop, not 'T' Stop (and magnification on the film however I don't want to start that one here!)

Stephen

[Ry Kawanaka]

I've always wonder how come samcine dof calculator has T-stop measurement as every lens has slightly different degrees of compensations. Does anyone have answer to this??

I know it's slightly off the topic but Mr. Williams post reminded me of this question...

Edited August 24, 2007 by Ry Kawanaka

[Patrick Neary]

Howdy all-

 

It seems to simplify things, Christian asked about slapping a 50mm onto a 16mm camera, in which case comparing fields of view doesn't really enter the equation, it's just a 50mm at f4 focussed at 12' (or whatever).

 

If you look at the DOF tables (in the AC manual) you get slightly less depth of field than the same lens set at the same distance at the same stop but on a 35mm camera, so you wouldn't want to use the 35mm DOF table. The only change is the size of the recording format.

 

aside, who came up with those CoC numbers anyway (kodak)? Are they universal or can they vary depending on which DOF table or wheel you're looking at?

[Stephen Williams]

I've always wonder how come samcine dof calculator has T-stop measurement as every lens has slightly different degrees of compensations. Does anyone have answer to this??

I know it's slightly off the topic but Mr. Williams post reminded me of this question...

 

Hi,

 

I don't have my MK II with me but I think on the bottom right of the calculator there is an offset for F & T stops AFAIR.

 

Stephen

[Jonathan Bowerbank]

Depth of field is based on focal length, distance to subject, and t-stop. Where the confusion comes in, is in the format, 16mm vs. 35mm. The confusion now is whats considered the field of view.

 

Excellent explanation Larry, I had an instructor once who included "format" into the factors of DoF, then another DP would turn around and say NO while pointing out the difference between DoF and FoV just as you have. This is why in the AC Manual there are separate tables for DoF and FoV.

[Patrick Neary]

I had an instructor once who included "format" into the factors of DoF, then another DP would turn around and say NO while pointing out the difference between DoF and FoV just as you have. This is why in the AC Manual there are separate tables for DoF and FoV.

 

FOV is something entirely seperate, but you have to include format when you're talking about DOF, because CoC numbers are different for each...

[David Auner aac]

DOF is connected to the 'F' stop, not 'T' Stop (and magnification on the film however I don't want to start that one here!)

 

Hi Stephen, I assume by magnification you mean the image reproduction ratio, right?

 

Cheers, Dave

[Stephen Williams]

Hi Stephen, I assume by magnification you mean the image reproduction ratio, right?

 

Cheers, Dave

 

Hi Dave,

 

Exactly, that and 'F' stop determine DOF.

 

Stephen

[David Auner aac]

Exactly, that and 'F' stop determine DOF.

 

I have been trying to get that into people's brains ever since I started working in this industry. I just don't get why so many books by real pros get this wrong. I guess that's the merits of growing up with a grandpa who was a pro photographer and an uncle who does the same...

 

Cheers, Dave

[Satsuki Murashige]

I've always wonder how come samcine dof calculator has T-stop measurement as every lens has slightly different degrees of compensations. Does anyone have answer to this??

I know it's slightly off the topic but Mr. Williams post reminded me of this question...

I have the Mk. 3 and it has f/stops on the left side and T stops on the right. The scales are offset by 1/2 stop, so if you set it to T1.4, the f/stop will be f/1.2. It's not exact for every lens obviously, but it's probably close enough for focus pulling. Plus, you'll notice that once you get up to about 50mm at those stops, you're depth of field is practically nil anyway so you can't really rely on DoF to cover your mistakes -- you have to hit focus precisely.

 

Also, most modern lenses like the Ultra Primes don't have f/stop markings on the barrel, so you'd have to use the T stop anyway to approximately calculate depth of field. It helps that modern prime lenses are very light efficient so the T stop is very close to the f/stop.

[Stephen Williams]

Also, most modern lenses like the Ultra Primes don't have f/stop markings on the barrel, so you'd have to use the T stop anyway to approximately calculate depth of field. It helps that modern prime lenses are very light efficient so the T stop is very close to the f/stop.

 

Hi,

 

Cooke S4's, Ultra Primes & Master Primes have DOF tables from the manufactures, corrected for entrance pupil position & T stops.

 

Stephen

[Dror Dayan]

Hi Everyone.

 

it may not exactly be the subject of this thread, but this is something that I don´t seem to understand and it bugs me, when shooting S16 with 35mm optics. I AC´d a student film last month, with the SR3 and BL optics, so we had 35mm optics on our camera. I asked the DoP if it means that we now have to use "wider" focal length, because if for example a "normal" lens for super16 is a 16mm, the 16mm from the BL will be too wide, no? he said the focal lengthes stay exactly the same. I just couldn´t understand how come it dosen´t make a difference if those are 16 or 35 optics. Because of the smaller format it´s like we´re "zooming in", so we should use wider optics to preserve our field of view, or so I thought. I know from photography that if you want to preserve a "normal" field of view for example with 35mm, middle-format or large-format, you have to use 50mm, 80mm or 135mm accordingly. dosen´t it also apply to film cameras?

 

thanks,

 

dror

[Stephen Williams]

Hi Everyone.

 

it may not exactly be the subject of this thread, but this is something that I don´t seem to understand and it bugs me, when shooting S16 with 35mm optics. I AC´d a student film last month, with the SR3 and BL optics, so we had 35mm optics on our camera. I asked the DoP if it means that we now have to use "wider" focal length, because if for example a "normal" lens for super16 is a 16mm, the 16mm from the BL will be too wide, no? he said the focal lengthes stay exactly the same. I just couldn´t understand how come it dosen´t make a difference if those are 16 or 35 optics. Because of the smaller format it´s like we´re "zooming in", so we should use wider optics to preserve our field of view, or so I thought. I know from photography that if you want to preserve a "normal" field of view for example with 35mm, middle-format or large-format, you have to use 50mm, 80mm or 135mm accordingly. dosen´t it also apply to film cameras?

 

thanks,

 

dror

 

Hi,

 

A 50mm lens is always a 50mm lens, how wide a circle that the light covers determines the largest format that the lens can be used on. Bear in mind that a lens used on a 16mm camera should ideally resolve more than one used for 35mm.

 

Your not zooming in, your cutting out the center!

 

Stephen

 

Stephen

[Jon Kukla]

One thing that was mentioned in the GBCT Techs magazine maybe a year ago was that 35mm format lenses sometimes have a problem in 16mm cameras in that the extra width of the image circle creates more light bouncing around the mount, which may have some veiling effect in the gate. It was all very circumstantial and controversial even there, but apparently it was noted by the rental houses and there were some minor but important modifications made to counteract this. To what extent this knowledge has circulated around the rental houses and so forth, I'm not certain. I'll try to look up the issue so as to provide a scan of the article.

[Jon Kukla]

Yeah, here it is, page 8: http://www.gbct.org/newsletters/TECHS_15_lr.pdf