Depth of Field on Film vs. Digital

[luigi bertolotti]

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Has anyone done test how to use the DOF-scale in digital times ?

 

DOF is such an elusive value to test and measure, that is better, imho, to use a very simple dumb's rule : use the lens DOF scale at ONE stop less than the one you are using.

Not scientific, but, in my experience, good for lenses from 35 to 90.

[Berlinman]

DOF is such an elusive value to test and measure, that is better, imho, to use a very simple dumb's rule : use the lens DOF scale at ONE stop less than the one you are using.

Not scientific, but, in my experience, good for lenses from 35 to 90.

 

 

Thanks, sounds good and very usable. I'm a physicist and I've learnd that calculating the DOF with all aspects is nothing You can do befor taking a picture !

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[MarkP]

DOF is such an elusive value to test and measure, that is better, imho, to use a very simple dumb's rule : use the lens DOF scale at ONE stop less than the one you are using.

Not scientific, but, in my experience, good for lenses from 35 to 90.

 

 

Exactly what I do, but I add another stop where it's more critical to get the focus right.

[tobey bilek]

DOF does not exist. There is but one plane of focus.

 

50 1.4 is not as sharp in the corners as Summicron. The two lenses are different and are markedly different in bokeh which is why I own the 1.4.

 

Digital images from the camera are soft, any digital camera. I would recommend learning to sharpen properly in stages and not focus and recompose.

 

I would not recommend focus and recompose because the one lens may have MORE field curvature than the other. 1.4 are generally not as flat as slower lenses.

But even the Summicron is not flat. In designs past, even the micro lenses, misnamed macro, are not perfectly flat.

[pgk]

DOF is about perception and certainly does exist. The problem with it is that most people want a simple, cover-all solution for DOF, whilst in actuality there are a large number of variables (surch as curved field) which need to be taken into account if what we see as a final is to appear to be 'sharp'. If all variables are known then DOF can be calculated, but in practice its unlikely that all are often known and we all too often examine images far to closely....

[plasticman]

I suspect it would if the film used is as fine-grained as "is" the sensor. If anything the pixel has sharper edges, by far, than does a filigree edge of a grain of silver. Digital has long since surpassed Kodachrome and probably will the microfilms as well soon enough. New rules-of-thumb to learn, that's all. I'd probably gain a stop of steadiness if I cut out the alcohol and coffee...

 

s-a

 

Photo Utopia: Clumps and Chumps (or why film isn't binary)

[yeeper]

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I work in film and TV and so does my wife: She's a Camera Assistant - the one that is in charge of focus. "Pulling focus", as we call it. In the switch from film to digital on movies, she noticed a very similar thing: You cannot "buzz" focus on digital: It is in or it is out. Buzzing focus is where you miss focus by a tiny bit, but it is passable. It still has enough acuity to not look bad.

 

Film has this bit of roll-off due to the three dimensional aspects of it as a "sensor". Each color is its own layer. Therefore, it is possible to miss focus on one or two layers but still catch it on another. That is the nice tapering off of focus on film. Even single-layer black and white has a tiny amount of depth. With digital, it is a clinically flat sensor plane. So now in movie/tv production on digital cameras, when you miss focus, you MISS it. There is no buzzing it and getting away with it.

[semi-ambivalent]

Photo Utopia: Clumps and Chumps (or why film isn't binary)

 

I'm having trouble understanding your point. (I'm also having trouble understanding the point of the blogger. I'll read it again tomorrow but I suspect his position fails or not based on scale. Small enough and it's all just bits of energy; not "solid" at all. I'm an existentialist, and if I see "grains", they're grains. But I know their edges are not sharp and I believe digital's pixels will eventually be smaller. The boffins have few other places to go with it. You know Cmosis has a 70MP FF sensor on the market right now, don't you?) I'll have to read it again.

 

Thanks,

s-a

[mjh]

I suspect it would if the film used is as fine-grained as "is" the sensor. If anything the pixel has sharper edges, by far, than does a filigree edge of a grain of silver.

Actually the grains of silver have sharply defined edges, see Kodak R&D: Chemistry-Silver Halide Emulsions for example. On the other hand they are neither square nor arranged in an orderly pattern as sensor pixels are. But the main difference lies elsewhere.

 

Some people have been comparing the size of sensor pixels to the size of the grain in silver halide film, but such a comparison isn’t actually valid. The sensor data tell you that within a certain area, the average brightness was such-and-such. A silver crystal in a film emulsion only reveals that two or more photons have hit the original silver halide crystal. That is you get very precise position data as the crystal is quite small, but next to no brightness data – it could have been nearly dark and there was just the one stray photon (well, two photons actually) hitting the grain or there could have been a bombardment of photons, but once the developer has reduced every grain containing at least one small part of metallic silver to pure silver, there is no way to tell the difference.

 

You need to look at a larger area and count the number of silver grains to determine their density, and from the density you can determine the brightness. Increasing the area gives you finer distinctions in tonal values as well as lower noise, but at the same time you lose position information. So there is a trade-off between brightness vs. position info. Assuming you have a sensor providing, say, 14 bits per pixel for distinguishing 16384 values with a certain amount of noise, you could try to determine how large an area of a specific emulsion you would have to evaluate to obtain a similarly fine resolution of brightness with similar noise. This area could then be usefully compared to the area occupied by a sensor pixel.

 

Having said that, in the context of DOF considerations it is far more relevant that emulsion layers have a certain thickness with grains deposited at different depths. Also with colour film (and some back&white film) there are several layers. The position of the image plane can vary by some tens of microns and still be somewhere within the layers of emulsions. This is in sharp contrast to a sensor that behaves like an extremely thin film.

Edited October 14, 2014 by mjh

[pgk]

So now in movie/tv production on digital cameras, when you miss focus, you MISS it.

There is a vast difference between accuracy of focus and DoF. DoF has not changed in terms of the way the image is formed (how could it?), however both the way we sample it (we now use a very thin flat plane) and how we assess what appears to be 'sharp' (we magnify far more, as a matter of course, to determine how much fine detail exists in the area we are interested in) has.

 

FWIW I am very wary of attempting to 'compare' digital and analogue systems, because they are so different. However, as I have said before on this forum, for scientific purposes current high end full-frame digital (colour) systems have provided me with more, and more usable, data when carrying out critical identification work based on details of the subject matter. So in terms of 35mm work, digital cameras can produce more image data than film, and I have carried out absolute comparisons in a real world test situation to check this. Data yield is not the absolute requirement of most images though so this needs to be taken within its context.

[pico]

Up to a point, more pixels per square mm does not mean greater capture of information or higher quality.

 

Digital noise is white. What we see as grain is black, translucent space between grain clusters.

[flyalf]

Im with mjh. My understanding is that analouge film records light not in one 2-D plane as digital does, but in 3-D layers into the film. This will affect DoF because the image is formed in different ways. If digiatl had layers of sensors on top of each other recording different colours this might be a bit like analouge film. But to have the image formed more like analouge the digital sensors would have to be distributed like film grains, that is "baked" into emulusion layers that have depth.

 

Beacuse of this and the general properties of digital I use the folloving rule-of-thumb for DoF; step down 1-2 apertures from DoF scale on lens.

[AlanSchaller]

Im finding the Monochrom paired with good glass gives a more natural (film like) and pleasing presentation to photos in comparison to any of the other digital cameras I have used and owned.

 

Here are some examples of my pictures on my Monochrom with 50mm and 35mm asph Summicrons.

 

https://www.flickr.com/photos/127753524@N02/

 

Alan.

[pico]

Im with mjh. My understanding is that analouge film records light not in one 2-D plane as digital does, but in 3-D layers into the film. This will affect DoF because the image is formed in different ways. If digiatl had layers of sensors on top of each other recording different colours this might be a bit like analouge film.

 

 

Consider the Fovean sensor.