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Quite Simply - Depth of Field

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Christopher Genovese

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I'm a new user, so please forgive me if this was either discussed previously or unknowable at this moment (I've searched far and wide in the forum, so I tried), but all I want to know if someone can tell me is what the depth of field range will be like on the Scarlet kit with fixed lens.

Does anybody know what the fixed lens will actually be? How will that influence DOF?

Can someone, a DP perhaps, explain what influences DOF in digital cameras specifically, how it differs from how DOF is controlled in shooting celluloid film (if it does)?

What would the Scarlet need to be for me to shoot shallow DOF both (lets say for example, having only a person's face in focus in Close Up) in daylight and firelight?

Thanks,
Chris
 
DOF is all to do with the sensor size, focal length of your lens, and the aperture you are using.

For example you are going to achieve much shallower depth of field (cinematic depth of field so to speak) using a camera with a 35mm sized sensor or close to (the Red One for instance), than a camera using a 2/3" sized sensor (the Scarlet) with the same exposure/relative lens setup.

The bigger the sensor, the shallower the depth of field (compared to a smaller sensor with same relative lens/aperture setup) put simply. Also, the longer the focal length (wide=deep DOF zoom=shallow), and the higher the aperture, the shallower the depth of field. Remember this is all relative. If you were to put a 105mm lens on a 35mm sensor based camera, then also a 2/3" based camera with the same exposure settings, the 35mm camera would have a shallower DOF.

The depth of field isn't affeted by whether it is digital or film, it's just when people think of film based motion picture cameras they tend to think of 35mm cameras which contribute to a shallow depth of field. In truth a 16mm camera has a very similar sized sensor to a 2/3" chip digital camera and will have similar DOF properties.

This image shows the different sensor sizes and is a good place to start;

http://www.hotrodcameras.com/wp-content/uploads/2009/06/sensor-size-chart-web2.jpg

Edit : I believe the Scarlet has a 2/3" sensor, and an 8x fixed zoom lens, so you will be looking at DOF comparable to 16mm film. You will be able to have very shallow DOF at full zoom in daylight, as for shooting by firelight, It highly depends on how bright that is. Shooting in such low light conditions would be extremely difficult and require an extremely fast (high aperture) lens. I'm not sure what aperture the Scarlet fixed lens is, some one can chime in here.
 
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Jamie Havill said:
If you were to put a 105mm lens on a 35mm sensor based camera, then also a 2/3" based camera with the same exposure settings, the 35mm camera would have a shallower DOF.
Click to expand...

This is actually not true. A 105 mm lens, if at the same aperture, will produce identical depth of field on either camera. However, the field of view on the 35mm sensor will be much wider than on the 2/3" - hence "crop factors". Depth of field is determined by the physical aperture size, and the camera-to-subject distance. You could use a wider lens on the 2/3" and open it up to give you similar (if not identical) field of view and depth of field to the 105mm used on a 35mm-sized sensor.

Good article on depth of field:
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

EDIT: also in response to the above - you would actually have more depth of field in daylight, as you would normally stop the lens down (unless you control the exposure through shutter speed or ND filters or such, instead). Shooting by firelight, if you can get a good exposure, would require a very fast lens as you said, and would result in much shallower depth of field than shooting stopped down in full daylight
 
Christopher

I'm going to start off here with some general points about DoF to get the ball rolling; I'm sure others will add comments and after a few posts you'll either be thoroughly confused or know what you need to know - hopefully :-)

First of all, DoF in a purely technical sense, depends on distance to subject (point of focus) and f-stop. So if you keep your subject at the same size in the frame at different focal lengths (by moving the camera closer of further away and changing your point of focus) the DoF at any given aperture will be the same. However, the resulting image from a 20mm lens and a 200mm lens will be vastly different, even though the DoF is the same, because the perspective at varying distances to the subject is different. The longer lens will 'compress' the background so that it looks bigger (closer) relative to the foreground and the DoF will appear to be shallower.

Here's a link that shows this very clearly: http://www.luminous-landscape.com/tutorials/dof2.shtml

Generally speaking the smaller the sensor size the harder it is to get a shallow DoF. Lenses are wider for the same field of view.

I would guess that the Scarlet will have a lens around 9-72mm (35 - 280mm in 35mm terms). To get shallow DoF for an interview say, shoot as wide open as possible (using ND filters to reduce the amount of light) and move away from the subject and increase the focal length. Or, move as close as you can to the subject and widen out the lens. These shots can have the same DoF but look quite different. Also, the further away your BG from the subject the better for shallow DoF, so try to shot in big rooms or outside.
 
1 min on Google =

David Mullen ASC said:
Practically speaking, at the same f-stop compared to S35, 2/3" is the equivalent depth of field of stopping down by 2.5 stops -- in other words, if you shoot at f/2.0 on a 2/3" camera, it's the same depth of field as shooting at a f/4.0-f/5.6 split in S35, assuming you match field of view and distance.

Super-16/16mm has the same issue -- doesn't something shot in 16mm look "filmic"? How about a 35mm movie with a deep-focus look, like "Citizen Kane"?

Plenty of 35mm photography is shot in the middle f-stop range, especially outdoors.

It's really only in night photography where the extra depth of field of 2/3" sensors is a bit uncharacteristic of 35mm night photography, which tends to be super shallow-focus.

Now if you like the look of 35mm shot at an f/2.8-f/4 split, it's a bit harder to do that on a 2/3" camera since you'd need an f/1.4 lens -- not impossible for a single-sensor camera that can use cine lenses, but the fastest 3-CCD HD lenses made tend to be f/1.6 (like a Zeiss Digi-Prime), which is probably close enough.

Fincher's "Zodiak" and the upcoming "Benjamin Button" were shot on the Viper, which has 2/3" sensors -- they seem fairly "filmic" to me...
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David Mullen ASC said:
Obviously you have to know what you are doing in order to control depth of field and not let it get deeper than you want, since you don't have an easy way of getting, let's say, the look of shooting at f/2.0 on 35mm when using a 2/3" camera. So I can't say that it makes no difference, the size of the sensor, just that it's a difference that can be dealt with to some varying degrees of success. A 2.5-stop difference in effective depth of field is manageable.

However, I just finished a TV show on a 35mm-sensor digital camera, when we had contemplated using a 2/3" camera... and I was glad we went with the 35mm-sensor camera in the end because we didn't shoot many close-ups on the show, lots of medium shots in small houses, at an f/2.8 generally, usually on a 35mm prime lens. So it was helpful to have the fall-off in focus since I couldn't get the walls farther away from the subject and we weren't pushing in tighter either to make the focus drop off faster.
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David Mullen ASC said:
You're ignoring two issues -- one is that since the smaller sensor crops the lens image more, you won't get the same field of view, so you'll want to compensate by changing focal length.

The other issue is that you have to change your Circle of Confusion factor if you are blowing up a smaller image to be the same size as a larger image. So the depth of field charts for a 50mm lens, for example, are different when that 50mm lens is on a 35mm camera versus a 16mm camera, because the Circle of Confusion figure is different if you are assuming the same size in final image presentation / display.

Of course, this is what Eki was saying at the top of the page.

Anyway, because you need to use shorter focal length lenses on smaller sensor cameras to get the typically desired fields of view, you can say that for practical purposes, smaller sensor cameras have deeper focus characteristics.
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David Mullen ASC said:
This is basic photography. The 2/3" sensor gives you an effective increase in depth of field as if you stopped down a 35mm cine lens by 2.5-stops once you match field of view by using a shorter focal length compared to 35mm cine (divide the focal length you would use on a 35mm movie camera by 2.5 to get the equivalent focal length in 2/3" -- so instead of a 50mm lens, you'd use a 20mm lens, for example.)

So if you shot at f/2.0 on your 2/3" camera, it would look like you were shooting 35mm at a f/4.0-5.6 split. Whether or not that is acceptably shallow-focus is up to you, but in your typical close-up, the background would be soft at that stop.

Rent "The Curious Case of Benjamin Button" or "Zodiak", both shot on 2/3" cameras and decide whether the backgrounds are soft enough in focus.
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Hope that helps. :thumbsup:
________
Digital Vaporizer
 
Kevin Marshall said:
This is actually not true. A 105 mm lens, if at the same aperture, will produce identical depth of field on either camera. However, the field of view on the 35mm sensor will be much wider than on the 2/3" - hence "crop factors". Depth of field is determined by the physical aperture size, and the camera-to-subject distance. You could use a wider lens on the 2/3" and open it up to give you similar (if not identical) field of view and depth of field to the 105mm used on a 35mm-sized sensor.

Good article on depth of field:
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
Click to expand...

That's why I say it is all relative. There's a good paragraph here that will explain what I mean;

"On the other hand, when standing in the same place and focusing on a subject at the same distance, a longer focal length lens will have a shallower depth of field (even though the pictures will show something entirely different). This is more representative of everyday use, but is an effect due to higher magnification, not focal length. Longer focal lengths also appear to have a shallow depth of field because they flatten perspective. This renders a background much larger relative to the foreground-- even if no more detail is resolved. Depth of field also appears shallower for SLR cameras than for compact digital cameras, because SLR cameras require a longer focal length to achieve the same field of view."

Say our original poster wants to get a close-up of a face with a really shallow depth of field. He's not going to use his widest lens, and go and stand in the persons face, ensuring the background is a nice long distance away. He's going to use a nice portrait lens, stand back and have the background thrown out of focus very easily, due to the properties of these lenses. This is much easier to achieve on larger sensor cameras, as you can use longer lenses along with wider lenses depending on what you want from the shot.

I meant to say if you were to use a lens that equated to a 105mm view point of each sensor, with the same aperture settings, the 35mm sensor would yeild a shallower DOF.
 
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Thanks. Yea, I'd appreciate anyone else' advice on this too.

Am I to believe that if I was to put a 105mm lens on a Scarlet with a 2/3" sensor, that the image passing through the lens would be cropped due to the smallness of the sensor? Where do the borders of the image truly finish then? If Red camera's are truly infinitely reconfigurable, wouldn't they eventually develop a sensor that was TOO BIG for the image passing through the lens?

I don't want to get off track here, I'm just interested in what I'm specifically getting if I buy a Scarlet, as far as DOF is concerned.

Side question: Also I was wondering does anyone know how a DP would describe DOF technically? Are they aware of the literal length measurement of the plain in focus, (e.g. this shot has a DOF of 88 millimeters) or do they just eyeball it?
 
Listen to what David Mullen has been quoted saying Christopher, and you will understand this quite easily. If you were to use a lens that would equate to 105mm on a 35mm sensor camera, you would then need to divide that by 2.5 to find that focal length lens would be required a 2/3" sensor to achieve the same field of view. In this case it would be 105/2.5 which is a 42mm lens. Now due to the step down in focal length by 2.5 to achieve the same FOV as a 35mm sensor due to crop factor of the 2/3" lens, you'd effectively have the same DOF as the 35mm camera if the aperture was decreased 2.5 stops.
 
Jamie Havill said:
That's why I say it is all relative. There's a good paragraph here that will explain what I mean;

"On the other hand, when standing in the same place and focusing on a subject at the same distance, a longer focal length lens will have a shallower depth of field (even though the pictures will show something entirely different). This is more representative of everyday use, but is an effect due to higher magnification, not focal length. Longer focal lengths also appear to have a shallow depth of field because they flatten perspective. This renders a background much larger relative to the foreground-- even if no more detail is resolved. Depth of field also appears shallower for SLR cameras than for compact digital cameras, because SLR cameras require a longer focal length to achieve the same field of view."

Say our original poster wants to get a close-up of a face with a really shallow depth of field. He's not going to use his widest lens, and go and stand in the persons face, ensuring the background is a nice long distance away. He's going to use a nice portrait lens, stand back and have the background thrown out of focus very easily, due to the properties of these lenses.

I meant to say if you were to use a lens that equated to a 105mm view point of each sensor, with the same aperture settings, the 35mm sensor would yeild a shallower DOF.
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You are confusing Depth of Field with Field of View.
 
Jamie Havill said:
Listen to what David Mullen has been quoted saying Christopher, and you will understand this quite easily. If you were to use a lens that would equate to 105mm on a 35mm sensor camera, you would then need to divide that by 2.5 to find that focal length lens would be required a 2/3" sensor to achieve the same field of view. In this case it would be 105/2.5 which is a 42mm lens. Now due to the step down in focal length by 2.5 to achieve the same FOV as a 35mm sensor due to crop factor of the 2/3" lens, you'd effectively have the same DOF as the 35mm camera if the aperture was decreased 2.5 stops.
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Okay, thanks Jamie. I hadn't gotten through all you're quotes before I responded to other replies, but I read it now so I understand. That really helps. And I'll rent Zodiak again!

Thanks everyone else. This is all a big help, not too much confusion.
 
Christopher Genovese said:
Okay, thanks Jamie. I hadn't gotten through all you're quotes before I responded to other replies, but I read it now so I understand. That really helps. And I'll rent Zodiak again!

Thanks everyone else. This is all a big help, not too much confusion.
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No problem Chris, I'm still learning too, hence why my information got a bit cloudy at points. Glad you understand some things now, and other more knowledgable people that us were able to help!

It seems people get to caught up in the scienece of theory of it. Just get out there and see what works for you, and what achieves the best results. For example, David Mullen (probably the most qualified guy on many of these threads) always quotes real life scenario's, and draws from his actual experience to answer questions.
 
Just a thought, but if really shallow DoF is important to you, for less money than Scarlet check out the new breed of DSLRs. They're not comparable to Red in many ways as they're stills cameras with video, but if all you need is HD resolution you can get crazy shallow DoF easily - and you can buy now!

Philip Bloom has may examples of DSLR footage on his web site:

http://philipbloom.co.uk/
 
Andy Taplin said:
Just a thought, but if really shallow DoF is important to you, for less money than Scarlet check out the new breed of DSLRs. They're not comparable to Red in many ways as they're stills cameras with video, but if all you need is HD resolution you can get crazy shallow DoF easily - and you can buy now!

Philip Bloom has may examples of DSLR footage on his web site:

http://philipbloom.co.uk/
Click to expand...

These new breed of DSLR's seem to me to have too shallow a depth of field.

edit : From what I've seen at least!
 
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One thing to keep in mind is that crazysexycool DOF (RE: 5DMk2) can make focus-pulling rather difficult, especially for the one-man band doing handheld without a lot of support gear.
________
FORD XB FALCON SPECIFICATIONS
 
Andy Taplin said:
Just a thought, but if really shallow DoF is important to you, for less money than Scarlet check out the new breed of DSLRs. They're not comparable to Red in many ways as they're stills cameras with video, but if all you need is HD resolution you can get crazy shallow DoF easily - and you can buy now!

Philip Bloom has may examples of DSLR footage on his web site:

http://philipbloom.co.uk/
Click to expand...

Wow, that's quite beautiful. But I'm going to have to go with the Scarlet, I'm not just interested in getting a certain kind of image but like many of us, forming a relationship with Red for many years and taking advantage of upgrades, customer service, etc.

Also, I'm too much of a slow motion whore.
 
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