Relay lens for 1/2" AND 2/3" sensors (for Dof adapters)

actually, I have to correct myself. I did use a relay once for a reason other than to connect a DoF adapter. It was to use a 35mm prime on a F900. You still maintain the 2/3" DoF because the format doesn't change-- because you don't use a DoF adapter-- however the FoV changes since it's on a relay. And you end up with MORE Dof than it would be on a 35mm system.

This doesn't go against what I've been saying, it just reinforces it.
 
Marshallarts said:
Doesn't that very much illustrate the point here? 16mm doesn't get us 35mm DoF. If it's dark out and you can't open up anymore, and don't want to compromise lens MTF & CA by opening up, that is a disadvantage to 16mm. That's why 35mm is better if you're want to achieve a smaller DoF (aka, a 35mm "look"). That's why we use "35mm DoF adapters"!!!

35mm and 16mm have very different DoF! The bigger the sensor size the shallower the DoF! This is 1st grade here!
Click to expand...

Actually this actually illustrates just the opposite. You can see that Jeff has zoomed in so that each shot has the same FOV, but this means that he's also working at different focal length. When you take into account the crop factor of the 2/3'' system (bare camera) the focal length used on the 2/3'' to achieve that same FOV has to be shorter than that used by the 35mm system. A shorter lens will *appear* to have be more in focus because it doesn't compress perspective quite as much.
 
Wow.........

The more I read the more I want to shake my head. I don't know what to say. And I apologize if at any time I sound inappropriate. I can't help but give up here. I'm starting a two week shoot tomorrow and won't have any time to respond. Huy, sorry, I may not get back to our discussion either.

I can't help but think maybe this is something you all don't know. It's basic 101 to me that 16mm has a larger depth of field than 35mm. And it's because of the circles of confusion. And if you don't know what "circles of confusion" are then you have no business arguing with me.

If anyone has even bothered to look at ANY DOF CHARTS OUT THERE!!!! they will see I am correct. For God's sake I"m looking at mine RIGHT NOW!!!!!! Everyone should have one. So look at it. Read the scales!! Why do you think you have so much DoF in video!!?? It's because you have a small sensor. I'm not getting techical about focal lengths and stuff, you're only confusing the matter. The smaller the sensor the larger the DoF! Drop the focal length issue.

If the semantics of what I'm talking about are what's making this confusing I can't apologize because this is the everyday practice for me. In practice what I'm saying is correct. I understand you can say FoV this and focal length this..... but when I say I want a shot with a particular on 16mm to match the same shot on 35mm, I know plain as day that the DoF will be different, that in 35mm it is shallower. This is so obvious to me it's killing me. haha.. geesh. I gotta get some sleep.

Thanks for all the discussion on this. Looks like I've taken the whole thing way more off topic than anyone else here. Guess we'll just have to agree to disagree. Just hope I'm there when we have to test this together in person, I want to win that contest. Unless it's backwards day or something

BTW, I mention 35mm instead of APS/Cine in the above examples just because it's easier to write, both way have shallower DoF than 16mm. 35mm being the shallowest. Also, as I've mentioned earlier, a lot of DoF adapters are intended for 35mm still lenses so that's a plausible option.

.....again... why do we even have 35mm DoF adapters if you all think there's no asthetic DoF to be gained??--that being you achieve 35mm DoF... That's what it's named after!

I'm speechless.
 
Huy Vu said:
Actually this actually illustrates just the opposite. You can see that Jeff has zoomed in so that each shot has the same FOV, but this means that he's also working at different focal length. When you take into account the crop factor of the 2/3'' system (bare camera) the focal length used on the 2/3'' to achieve that same FOV has to be shorter than that used by the 35mm system. A shorter lens will *appear* to have be more in focus because it doesn't compress perspective quite as much.
Click to expand...


Sorry man.. Again, you're talking about the focal length multiplier.

Please.. listen to me. look up what i've talked about. You have something to learn.

CIRCLES OF CONFUSION!! Look it up. I'm looking at it in wikipedia right now. http://en.wikipedia.org/wiki/Circle_of_confusion This is why 35mm has less DoF than 16mm. It's indisputable. Crop factor is a completely unrelated issue. There is no *appear* to it.

Also, you're use of FoV is confusing. It's not necessary.

CoC.....
 
I just googled "why does 16mm have a larger dof than 35mm" and the very first article that came back says what I'm saying "35mm is still a large negative, and can allow you to get a very shallow depth of field.", "Super 8mm film has a larger depth of field and is often compared to 1/3″ CCD prosumer HD cameras."


...............................and even better.... My very next google, second thing I googled, was "16mm dof versus 35mm". and the first thing that came up illustrates this: http://www.mediachance.com/dvdlab/dof/index.htm

I gotta stop wasting my time doing your homework.
 
Marshallarts, I'm afraid you're not reading these posts very carefully.
My post mentioned that a 50mm lens on a 35mm gate will have slightly more DOF than a 50mm on 16mm or 2/3" gate both at the same T-stop. I won't go into the reasons why, my chicken is boiling and I have to make call time tomorrow.

I made my living as a 1st AC focus pulling for five years before just DP'ing. This stuff was critical to know. Huy is not all wrong and neither are you. You're just misinterpreting what other have posted. It doesn't even matter. What matters is that you shoot great movies :)
 
I think there is quite some misinformation in this thread.

A lens with a focal length of 50mm at a given f-stop will give you the same DOF no matter on what camera you use it. What changes is the FOV.
For example: A 50mm lens at 2.8 on a 35mm cine camera will give you the same DOF as a 50mm lens at 2.8 on a 16mm camera. What changes is the FOV ---> the 35mm cine camera will give you a wider FOV than the 16mm camera. This is because the 16mm camera "records" a smaller part of the image projected by the lens than the 35mm camera.
In order to achieve the same FOV on the 16mm camera as you get on the 35mm camera, you would need to use a shorter focal length. As a consequence of this you get larger DOF.
(Note: There are other factors that influence the DOF. I assumed that we use the same value for the COC for both formats in the calculation of the DOF. Depending on what value you choose for the COC you might get different results. A very good article that explains how the COC relays to DOF -->http://www.vanwalree.com/optics/dof.html)

Consumer video cameras usually have very small sensors. To get the same FOV as a 35mm cine camera with a 50mm lens, you need a very short (7-10mm) lens. This results in very large DOF. This is where the 35mm adapter comes in. The lens projects it's image onto a GG that has the size of a 35mm academy film frame. Therefore the FOV of the projected image is the same as if the lens would be mounted directly to a 35mm cine lens. You then use your camcorder to capture the image projected on the GG.
 
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Cordvision, what you are writing is commonly believed. Both you and Huy and others have posted the same thing. I thought it was as simple as that for a long while myself.
I guess I should have shut up about it. But it's a little troubling to see people post this misconception again and again. Experienced focus pullers know this. There's a slight variance to a focal length's DOF as it hits the film plane/sensor that has to do with the size of the film or sensor. It's not much, but it's there and it has to do with how focus is achieved on the imaging plane, and what exactly "focus" is - what's in and what's out of focus.

It's because of circles of confusion, and they change according to the size of the format. Thats why you get a bit more on the larger formats. I didn't want to pull out the "circles of confusion" bit, but I thought I'd get that technical to try to put these arguments to rest. A 50mm at a given f-stop will NOT give you the same DOF on ANY camera you use with it. Close but not exactly the same.
 
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dadoboy said:
Cordvision, what you are writing is commonly believed. Both you and Huy and others have posted the same thing. And I thought it was as simple as that for a long while myself. But there's a slight variance to a focal length's DOF as it hits the film plane/sensor what have you that has to do with the size of the film or sensor. It's not much, but it's there and it has to do with how focus is achieved on the imaging plane, and what exactly "focus" is - what's in and what's out of focus.
Click to expand...

That is simply not true! Imagine having a 16mm camera with a pl mount lens and a 35mm camera also with a pl mount lens. Now you use on both camera the same lens. You use in both cameras also the same film stock. In the 35mm camera you just record (on film) more of the projected image circle than you do in the 16mm camera.

Another way of illustrating it: You mount a lens in front of a wall so it projects an image onto the wall. Now you pin a 16mm film frame onto the wall and leave it there till it is exposed properly. You do the same thing with a 35mm film frame. The only difference is that you will have more of the projected image recorded on the 35mm frame than on the 16mm frame. You could cut the 35mm frame down to the size of the 16mm frame and you would end up with two identical images.

If somebody wants to dispute that he should better bring an explanation....

(PS: you might get slightly different results if you record to different mediums because light "scatters" (is there a better word?) a little different when it hits film than when it hits a ccd/cmos sensor)
 
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I'll tell you, what clued me in a while back was my Depth of Field charts! I thought the same as Huy and you but nope. Change it over to a different format, and the DOF changes because of circles of confusion. Sorry I can't give a better explanation, I just know it's true from doing it too.
 
dadoboy said:
I'll tell you, what clued me in a while back was my Depth of Field charts! I thought the same as Huy and you but nope. Change it over to a different format, and the DOF changes because of circles of confusion. Sorry I can't give a better explanation, I just know it's true from doing it too.
Click to expand...

Exactly, it changes if you use different COC values (as I noted above). If you use the same COC values, it doesn't change. Try it out with a DOF calculator that allows you to set the COC value manually. The COC becomes an issue if you enlarge the image. If the enlargement factor for your 35mm negative is the same as it is for your 16mm negative (when you project it), the COC value is the same....

(now I have to go to bed.... it's laaaaaateeeee)
 
Hey,

The thing is one must change the CoC when determining DoF. It's critical. It's the very reason why DoF changes, this is the backbone of DoF. On a DoF wheel chart it's the very first step in making the calculations to find DoF.

I wouldn't consider it a small thing even though it changes by a tiny fraction of a millimeter. This small change is what causes the entire phenomenon, and is 100% tied to the boken (another important term, wasn't going to pull that out either).

Again, I should apologize for getting so worked up here. Silly of me. Because you all have great feedback and are correct in what you're saying (except that the DoF doesn't change part:))

Cordvision, I agree with how you're describing the lenses in terms of FoV. But CoC is what determines the DoF. And using the correct CoC is the backbone in determining Dof. It's as critical in determining DoF as identifying what ISO you're film is when using a lightmeter to calculate what f/stop to use--a critical step

Here's panavision's online DoF chart -- under format you change the Coc. A critical step. http://www.panavision.co.nz/main/kbase/reference/calcFOVform.asp

Dadoboy, thanks for coming to the rescue. Actually I was getting a little worried there. And discussing this can get confusing so I apoligize. I never meant to compare a 50mm 16 lens at the same f/stop to a 50mm 35 lens. Because the shots are different. But with a 50mm 35 lens and a 25 (or 50 equivelent) lens on a 16 camera isn't your comment backwards?-"...35mm gate will have slightly more DOF than a ..... 2/3" gate both at the same T-stop". 35mm gate has slightly less (as in shallower) than a smaller format.

Have a good shoot, I'l LATE!
 
Marshallarts said:
The thing is one must change the CoC when determining DoF. It's critical. It's the very reason why DoF changes, this is the backbone of DoF. On a DoF wheel chart it's the very first step in making the calculations to find DoF.
Click to expand...

I depends on how you look at the footage, if you window the 35mm footage and compare it to the 16mm footage, you don't have to change the COC. If you use the same enlargement factor when projecting the negatives, you also don't have to change the COC. The image captured on the negative is in both cases identical! The COC comes into play when you enlarge one image more than the other. This happens while projecting the image but not when you record it (Important here, I am comparing 16mm film to 35mm film, both cameras loaded with the same film stock, this is important because in this case you have the same "resolution"/negative area in both formats).



Marshallarts said:
I wouldn't consider it a small thing even though it changes by a tiny fraction of a millimeter. This small change is what causes the entire phenomenon, and is 100% tied to the boken (another important term, wasn't going to pull that out either).
Click to expand...

...and is 100 % tied to the boken... do you mean bokeh? If so, the bokeh is tied to the shape of the aperture and hasn't much to do with the COC....
 
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Marshallarts,
I know it seems counter-intuitive that a 50mm lens through a 35mm gate will have more DOF than through a 16mm gate at a given stop. But it's true.
When I was AC'ing. I always found pulling with an 85mm on 16mm more challenging than an 85mm on 35mm wide open. 85mm and longer on 16mm at low light levels can put hair on your chest!

We often think of 16mm as having more DOF in all circumstances than 35mm, but the facts and my experience don't bear this out. Try it on your Depth of Field calculator, or just google "depth of field caculator" and punch in the numbers. I can't vouch for any of the ones online - I have one on my palm pilot and I have paper charts that I've used and an ASC book somewhere.

I can't say I enjoyed my work as an AC, it's a demanding and very technical job, but one of the things it provided, other than money, was a chance to see theories in action. I can understand visually why a smaller circle of confusion will lead to LESS DOF for a given focal length compared to a format with a larger circle of confusion.

That's why pulling focus on a 70mm HD zeiss digi prime at 1.4 can be brutally difficult!
 
cordvision said:
I depends on how you look at the footage
Click to expand...
And I never said it didn't. The Panavision On-line DoF calculator goes over every one of those possibilities and includes the corresponding CoC references. If anyone's bothered to look into any of the references I've already made. The original issue is that people didn't believe me when I said 16mm has more DoF than 35mm.

cordvision said:
...and is 100 % tied to the boken... do you mean bokeh? If so, the bokeh is tied to the shape of the aperture and hasn't much to do with the COC....
Click to expand...

Yes, I meant Bokeh, mistyped. And yes the aperture determines the shape of the bokeh. But I'm still correct in what I wrote. To avoid anymore confusion, I'm shutting up and letting the facts talk. (These are direct references, I should have made them days ago but still only took a minute to find)

**********************************************************

Boken - Bokeh characteristics may be quantified by examining the image's circle of confusion. In out-of-focus areas, each point of light becomes an image of the aperture, generally a more or less round disc. (reference: http://en.wikipedia.org/wiki/Bokeh)

Depth of field and sensor size -

As sensor size increases, the depth of field will decrease for a given aperture (when filling the frame with a subject of the same size and distance). This is because larger sensors require one to get closer to their subject, or to use a longer focal length in order to fill the frame with that subject. This means that one has to use progressively smaller aperture sizes in order to maintain the same depth of field on larger sensors. (reference: Cambridge in Color Digital photography tutorial) continue reading before you start talking about FoV, remember, these are direct quotes

So the bottom line - and all you really need to know - is that DOF is inversely proportional to format size. Note that format size is inversely proportional to the "digital multiplier". The higher the "digital multiplier", the smaller the format and thus the greater the depth of field. Note also that now you can see one of the reasons large format camera users need tilts and swings to get adequate depth of field. With an 8x10 camera you have about 8.5 times LESS depth of field than you do with 35mm for the same image. This also explains why consumer digicams, some of which have sensors 1/6 the size of 35mm film, have such a large depth of field and one of the reasons why it's almost impossible to get blurred backgrounds when using them.
I'm sure some people will say, OK, but what if you don't take angle of view into account. What's the relative DOF if you use the SAME lens on a small-sensor camera and a full-frame camera?
Now you run into the problem of what you are comparing to what. The same lens on the two formats will give you different fields of view, so if you enlarge each image to the same size (say 8x12), you won't have the same print so you really can't compare DOFs. If you crop the 35mm negative to give you the same print as the digital image the answer is easy. The DOF in the cropped 35mm print and digital image print will be exactly the same. You're using the same lens and same size image (cropped 35mm or digital), so you get exactly the same DOF.
What if you don't crop? Well, you have different views, but you can still compare DOF I guess. The focal length of the lens is the same in each case, so the ratio of the DOFs is just the ratio of the circle of confusion values, 18.45 microns for the small-sensor camera, 29.5 microns for the 35mm film. The ratio is 1.6x - there's that number again! The small-sensor image now has less 1.6x DOF than 35mm - but note that it still has at least 1.6x more DOF than the 35mm film would have if an 80mm lens had been used with the film camera to give the same field of view as the 50mm lens on the small-sensor camera. (reference: photo.net)

****************************************************

I'll stop here since my point was made and this can go on FOREVER...

And before anyone starts to drag FoV into this conversation again to defend their statement, let me first say my original posting had nothing to do with FoV, it was simply something you brought into the conversation in efforts to dispute my claim. It's superfluous to the original facts I made.

And if anyone points out these reference still photography instructions, it's because quite honestly it appears cinematographers don't know much about photography. Since I'm both maybe I appreciate the understanding of this more. Unless you don't really care in the first place, if you wish to accurately calculate DoF you need to take into account format size.

If you're sloppy or simply it's not as important to you. Don't bother replying to dispute these facts.
 
This is precisely why we feel it's so important to ensure that a full FOV is maintained for a given lens used with our system, either via our B4 relay, or otherwise. We don't believe in promising zero vignettting while advising our users to just zoom in to clear it. This effectively kills the FOV of your lens kit and makes DOF calculations and focal length choices very confusing. We have 8 choices of imaging elements, 4 for the smaller form factor cams, and 4 for the larger...all designed to provide maximum frame width with choices in bokeh rendition.

Bokeh is something we've worked very hard on specifically because the imaging element used can profoundly affect bokeh rendition. This is very confusing to those who haven't used them, but a quick look at our CF1/2/3 clip in Cinevate's Video University will make it visually obvious. CFX and CFXL is our best yet in terms of film accurate DOF (in other words, what you'd expect with actual film) across the usable aperture range. There's another clip at our site that explains also that light loss with our CF1 and CF1le elements behaves very different from what is predicted....in other words with a 50mm lens stopped down to f5.6 on our adapter system, you're only loosing 1 stop to the camera. This was so hotly debated it actually prompted a quick clip with the camera tethered to a waveform monitor...and prompted the creation of Cinevate's Video University altogether. Rather than argue, we just shoot videos and post them up :-)

The point of all of this is that the adapter, optics and taking lens all profoundly impact light loss, bokeh rendition, and DOF rendering. By DOF rendering I mean that you can tune bokeh while also maximizing light efficiency. Test the current crop of adapters at f5.6 and you'll see what I mean. Light loss figures quoted are nearly meaningless if they're not measured with a 35mm lens set at various apertures out front.
 
I think we are running in circles and we both generally agree with each other. (And we are faaar of topic :) )

I only disagree with two points in your last post and both deal with the exact same aspect.

Marshallarts said:
And I never said it didn't. The Panavision On-line DoF calculator goes over every one of those possibilities and includes the corresponding CoC references.
Click to expand...
This DOF calculator has fixed values for the COC for each format and assumes that you look at the footage on a cine screen. The value for the COC isn't a given factor. It is a subjective value that describes what you consider to be acceptably sharp and what not. The value you choose for the COC is different if you watch the footage on a big cinema screen than it is if you watch the movie on your TV.

Marshallarts said:
What if you don't crop? Well, you have different views, but you can still compare DOF I guess. The focal length of the lens is the same in each case, so the ratio of the DOFs is just the ratio of the circle of confusion values, 18.45 microns for the small-sensor camera, 29.5 microns for the 35mm film. The ratio is 1.6x - there's that number again! The small-sensor image now has less 1.6x DOF than 35mm.
Click to expand...
If you don't crop and if you enlarge both negatives wit the same enlargement factor, the same value of the COC applies for both formats ---> same DOF. What you quoted is true if you project both negatives fullscreen on a cine screen (which means that you have to enlarge the 16mm negative more than the 35mm negative to fill the screen).


PS: I am not looking to get into a fight about this or anything. It is still meant in a friendly way....
 
dadoboy said:
Marshallarts,
I know it seems counter-intuitive that a 50mm lens through a 35mm gate will have more DOF than through a 16mm gate at a given stop. But it's true.
When I was AC'ing. I always found pulling with an 85mm on 16mm more challenging than an 85mm on 35mm wide open. 85mm and longer on 16mm at low light levels can put hair on your chest!

We often think of 16mm as having more DOF in all circumstances than 35mm, but the facts and my experience don't bear this out. Try it on your Depth of Field calculator, or just google "depth of field caculator" and punch in the numbers. I can't vouch for any of the ones online - I have one on my palm pilot and I have paper charts that I've used and an ASC book somewhere.

I can't say I enjoyed my work as an AC, it's a demanding and very technical job, but one of the things it provided, other than money, was a chance to see theories in action. I can understand visually why a smaller circle of confusion will lead to LESS DOF for a given focal length compared to a format with a larger circle of confusion.

That's why pulling focus on a 70mm HD zeiss digi prime at 1.4 can be brutally difficult!
Click to expand...

Okay. Here we go. PANAVISION DoF chart (we agree Panavision knows best, right?) Using your 85mm lens example on a super 16mm camera:

SUBJECT DISTANCE:
20 feet

APERTURE: f5.6

FOCAL LENGTH OF LENS & FORMAT:
85mm on Super 16 1.78 HDTV TV Transmitted (CoC=0.0005mm)
170mm on Super 35 1.78 HDTV TV Transmitted (CoC=0.001mm)
*given a ~2x conversion from s16 to s35



Super 16 1.78 results:
Dof Near: 18.872'
Dof Far: 21.2714'
Dof Total: 2.3994'
Hyperfocal distance: 329.947'
Angle of View (Horizontal): 7.9 degrees
Field of View - width: 2.7647'
Field of View -height: 1.5529'

Super 35 1.78 results
Dof Near: 19.4276'
Dof Far: 20.6071'
Dof Total: 1.1795'
Hyperfocal distance: 659.894'
Angle of View (Horizontal): 8.1 degrees
Field of View - width: 2.8235'
Field of View - height: 1.5882'

16mm has a larger DoF than 35
 
what dadoboy says is true. Here is the example straight from panavisions DOF calculator.... (dadoboy, used the same lens for his example. Marshallarts, you used the same FOV for your example and therefore chose lenses with different focal length. So you aren't talking about the same thing. Dadoboy's example is true because you need to enlarge the 16mm negative more to project it onto a given cine screen than you need to enlarge the 35mm film negative. Therefore you need to choose a smaller value for the COC in the 16mm format. This is why your DOF is shallower in the 16mm format in this example. (The same principle applies that I tried to explain in my above posts))

Super 16mm
Subject Distance: 13m
Focal Length of lens: 85 mm
Aperture: f1.4
Format: Super 16 1.78 HDTV TV Transmitted (CoC=0.0005mm)

Dof Total: 0.8356m


35mm
Subject Distance: 13m
Focal Length of lens: 85 mm
Aperture: f1.4
Format: 35mm 1.85 Projected (CoC=0.001mm)

Dof Total: 1.6764m
 
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Oh sorry, didn't see those other posts here before I did my little "test".

Great info Dennis! I really truly look forward to learning more about your relay and hopefully using it! Much appreciated and good to get me back on track here.

I apologize for being the most responsible for taking this thread off topic. I'm getting upset at others who defend their points yet I'm the one whose trying the most to defend my point. I guess I knew bringing FoV into this would further complicate a subject I didn't intend getting into in the first place. And then I kept getting more agitated the more FoV was being used to dispute me.
 
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