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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

CINEPHOTOGRAPHY tools

Jarred Land said:
we will get all this stuff into an phone app at some point.. nice thing to have on an ipad on set.
Click to expand...

Why not having this very helpful calculator for Macbook Pro or Mac Pro as well, as a separate application without the need to go through the tools section???? Is it possible????
 
The DOF calculator has a parameter that is confusing me. In fact, it's contradicting my fundamental understanding of how sensor crop works with One, Epic, and Scarlet cameras. I have always thought that sensor crop, lens crop, and post crop, were all essentially doing the same thing with these three cameras.

It boils down to this question: Why does sensor crop change the DoF in this calculator?

As I understand it, sensor size will affect DoF on other cameras because the distance between the lens and sensor is set so that as much of the image projected from the lens onto the sensor, can be captured. EG: a 1/3" sensor is placed closer to a 50mm lens than a 4/3" is, so the 4/3" will have a much smaller DoF than the 1/3". But doesn't sensor crop keep the same distance between the lens and the sensor? EG: 4K-HD is the same distance from the lens as 2K-HD, therefore the DoF should be the same... But on this calculator, it's chopped in half. Why?
 
Aaron Shirley said:
The DOF calculator has a parameter that is confusing me. In fact, it's contradicting my fundamental understanding of how sensor crop works with One, Epic, and Scarlet cameras. I have always thought that sensor crop, lens crop, and post crop, were all essentially doing the same thing with these three cameras.

It boils down to this question: Why does sensor crop change the DoF in this calculator?

As I understand it, sensor size will affect DoF on other cameras because the distance between the lens and sensor is set so that as much of the image projected from the lens onto the sensor, can be captured. EG: a 1/3" sensor is placed closer to a 50mm lens than a 4/3" is, so the 4/3" will have a much smaller DoF than the 1/3". But doesn't sensor crop keep the same distance between the lens and the sensor? EG: 4K-HD is the same distance from the lens as 2K-HD, therefore the DoF should be the same... But on this calculator, it's chopped in half. Why?
Click to expand...


No all sensors are placed at the same distance to a 50mm lens... the distance is always 50mm to the nodal point of the lens.

How ever, the bigger sensor area the longer lenses you can use and still get the same field of view. And as longer lenses gives a smaller DOF.
 
Aaron Shirley said:
The DOF calculator has a parameter that is confusing me. In fact, it's contradicting my fundamental understanding of how sensor crop works with One, Epic, and Scarlet cameras. I have always thought that sensor crop, lens crop, and post crop, were all essentially doing the same thing with these three cameras.

It boils down to this question: Why does sensor crop change the DoF in this calculator?

As I understand it, sensor size will affect DoF on other cameras because the distance between the lens and sensor is set so that as much of the image projected from the lens onto the sensor, can be captured. EG: a 1/3" sensor is placed closer to a 50mm lens than a 4/3" is, so the 4/3" will have a much smaller DoF than the 1/3". But doesn't sensor crop keep the same distance between the lens and the sensor? EG: 4K-HD is the same distance from the lens as 2K-HD, therefore the DoF should be the same... But on this calculator, it's chopped in half. Why?
Click to expand...

Hi Aaron.

I think your question is answered if you think of the DoF as, I guess we can call it, a relative perception. That has to do with the so called "circle of confusion". So, when you are cropping the sensor, the image perceived (and recorded) has less resolution. Hence the perception of focus is greater in relation to the resolution because, talking in a non scientific way, the overall image looks more "out of focus", so for an object in a 2K image to be perceived really out of focus, it should be more out of focus than in the same image in 4K.

Please, someone correct me if I'm wrong.
 
See, both of these answers have exceptions I could go into (back focus adjustment, lens on an iPhone, pin-hole cameras, etc), but in both examples, you would think that DoF would double, not get chopped in half by halving the size of the sensor:

"The Bigger the sensor, the longer the lens = shorter DoF"- so doubling the sensor size, should double the length of the lens used to cover the FoV, which should halve the DoF... but the opposite happens in this calculator.

"cropping the sensor, the image ...has less resolution. Hence the perception of focus is ...the overall image looks more "out of focus", so for an object in a 2K image to be perceived really out of focus, it should be more out of focus than in the same image in 4K"- this concept works if you're talking about perception of a 2K image vs a 4K image both projected onto, let's say, a 40' screen, but if we're talking about cropping, then let's imagine we're talking about a 2k image vs a 4k image being shown at a 1:1 pixel ratio on a 4K monitor. You look at the 4K image and see what's in focus and out of focus, then you look at the 2K cropped image... has anything changed focus wise? Now, let's say we take that 2K image and scale it up to 4K. Over all it's going to look softer from the same viewing distance as the original 4K image, but that includes the center of the DOF, so relatively speaking, all of the just barely in focus spots should remain just as in focus as the center of the DOF part of the image (let's say: 'twice as blurry' than they were at 2K 1:1), just as things outside of the DoF area will become 'twice as blurry' as they were at 2K, and things way out of the DoF will also become 'twice as blurry'.

So neither explanation here (if I understand them correctly) explains why an object just inside of acceptable DoF at 4K suddenly becomes out of focus when the RED camera is switched to 2K. Are you both saying that sensor crop and post zoom'n'crop have different effects on the size of the DoF?

Björn Benckert said:
No all sensors are placed at the same distance to a 50mm lens... the distance is always 50mm to the nodal point of the lens.

How ever, the bigger sensor area the longer lenses you can use and still get the same field of view. And as longer lenses gives a smaller DOF.
Click to expand...

Jordi Figueras said:
Hi Aaron.

I think your question is answered if you think of the DoF as, I guess we can call it, a relative perception. That has to do with the so called "circle of confusion". So, when you are cropping the sensor, the image perceived (and recorded) has less resolution. Hence the perception of focus is greater in relation to the resolution because, talking in a non scientific way, the overall image looks more "out of focus", so for an object in a 2K image to be perceived really out of focus, it should be more out of focus than in the same image in 4K.

Please, someone correct me if I'm wrong.
Click to expand...
 
Ok, Aaron, I've checked back the cinephotography tool and I'm with you. I thought you said the DoF got bigger when going to 2K (which is the point I defended), but certainly, the DoF when changing from 4K to 2K it gets shallower, which is the opposite of what I was saying. So I'm with you: it confuses me too.

Can someone explain?
 
3' min? Is it possible to get a bit closer. To minimum focus at least? On the RPZ that is about 2" from the glass. Thanks guys.

Jarred Land said:
we will get all this stuff into an phone app at some point.. nice thing to have on an ipad on set.
Click to expand...
 
Jordi Figueras said:
Ok, Aaron, I've checked back the cinephotography tool and I'm with you. I thought you said the DoF got bigger when going to 2K (which is the point I defended), but certainly, the DoF when changing from 4K to 2K it gets shallower, which is the opposite of what I was saying. So I'm with you: it confuses me too.

Can someone explain?
Click to expand...

Its a bit tricky to talk about DoF and CoC but lets try.
Usually people wrongly state (old misconception) that bigger sensor gives shallower DoF. This is indirectly true only due to practical circumstances.
DoF is determined by 5 factors:
1. sensor size
2. focal length
3. focusing distance
4. aperture

OK that's 4, and the 5th one is almost always left out:
5. size of the viewing picture combined with the viewing distance

This is where, usually left out DoF story, CoC (circle of confusion) comes into picture. We can differentiate between print/screen (p/sc) CoC and sensor CoC.
Print/screen CoC is defined as the largest diameter of a "point" at which this point still looks acceptably sharp or in focus - and p/sc CoC is defined for the picture we look at, be it screen or print. Again p/sc CoC is defined for the picture we look at.
It turns out that for the "normal" viewing conditions, the bigger the picture the more distance there is between us and the picture. The bigger the picture the bigger the p/sc CoC - ONLY if we assume the bigger viewing distance.
Now lets map this p/sc CoC to the sensor. How do we do that? Easy - divide the diagonal of the viewing picture - screen with the diagonal of the active part of the sensor.
I.e. picture is 350mm in diameter and it's p/sc CoC = 0.28mm (if we assume viewing distance of 350mm)
Sensor diagonal is 35mm. We can say that the magnification factor between sensor and the viewing picture (screen) is 10. Therefore sensor CoC = p/sc CoC / 10 = 0.028
Ok take a little break :-)


Aaron Shirley said:
Now, let's say we take that 2K image and scale it up to 4K. Over all it's going to look softer from the same viewing distance as the original 4K image, but that includes the center of the DOF, so relatively speaking, all of the just barely in focus spots should remain just as in focus as the center of the DOF part of the image (let's say: 'twice as blurry' than they were at 2K 1:1), just as things outside of the DoF area will become 'twice as blurry' as they were at 2K, and things way out of the DoF will also become 'twice as blurry'.

So neither explanation here (if I understand them correctly) explains why an object just inside of acceptable DoF at 4K suddenly becomes out of focus when the RED camera is switched to 2K. Are you both saying that sensor crop and post zoom'n'crop have different effects on the size of the DoF?
Click to expand...
Not really.


Now let's continue with the optical and sensor part of DoF.
There is only one distance where a point is "perfectly" sharp in the DoF (point is a point). Sharpness gradually falls off in front and behind this distance. Point starts to have an increasing diameter.
Let's assume we are recording in 4K resolution - active sensor diagonal is X and approx. sensor CoC = 0.02 mm (coming out of magnification and viewing picture formula)
You now make a note of a point on the edge of DoF of a picture/screen - on the sensor it has a diameter of 0.019mm
Now you switch to 2K resolution - you have a cropped image, but the noted point is still in the frame.
Active sensor diagonal is X/2. So image on the sensor will need to be magnified 2x more than the 4K image to cover the same viewing screen. approx sensor CoC = 0.01 mm.
Note that the image on the active part of the sensor has not changed - the noted point still has a diameter of 0.019mm - but according to CoC formula that is higher than the acceptable CoC of 0.01mm when recording to X/2 diagonal.
In essence the same point which is not in perfect focus is being magnified 2x more when recording in 2K related to 4K resolution. This magnification "pushes" the point out of focus (out of acceptable sharpness) on the viewing screen.

Same principle makes it harder to find critical focus on the 5" LCD. You think you nailed it, but when looking on a bigger screen from a relatively smaller distance you notice you missed the focus mark.
And you are able to notice that due to the bigger magnification.
Strange conclusion coming out of this is that for the same viewing distance - a bigger screen will decrease DoF even though you change nothing on the scene and camera side :-)
 
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Marko Hocevar said:
...There is only one distance where a point is "perfectly" sharp in the DoF (point is a point). Sharpness gradually falls off in front and behind this distance...
Click to expand...

Thanks for that great explanation, I see what I was missing now! I guess I've spent so much time shooting in lower resolutions like 16mm, 1080, and SD, that I've always thought of CoC as something you could "crush" or "clip" your area of focus into (as you would with your shadows and highlights) so you'd just have an even focus from the edge of near acceptable focus to the edge of far acceptable focus. Which to be honest, never felt right to me, but seemed to look true when I'd double check my focus in post.

I guess with all of this extra resolution, you can more easily see how the physics of light work.
 
Just downloaded. Great! Thank you RED-team and Brent for posting, very nice of you!
 
This IOS Redtools app really needs it's own thread to help publicise it.
 
In the recording time section for Dragon there aren't any obvious resolutions for anamorphic shooting. Do we just tap in 4K 5:4 and other 5:4 settings for an accurate calculation when using anamorphic lenses or will there be an update for anamorphic?
 
Crop Factor DOF??? i know there is too much info about it... but i make a test shot, all de shots, 5Kws, 4Kws, 3Kws, and 2Kws are in the same position and i didnt change the focus. I do not see any diference on DOF...thank you for comments.

https://youtu.be/kVHLS1RhHp4

DOF* not DOP
 
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