film latitude

[Kenneth Lau]

Can anyone explain to me, in some simple terms, what ' Film Latitude ' mean??

[Grug]

It's the exposure range (the range from black to white) within the image. The greater the latitude, the smoother the gradation between different levels of exposure within the frame will be, and the more apparent 'depth' the image will have (because you can see more detail in both the shadows and the highlights).

[TheDingo]

If you take a look at the latitude chart from the Single Chip Camera Evaluation from 2011, you will see that film shows about 14 stops of exposure latitude, and the ARRI Alexa was the only video camera to match this latitude range.

2011 Single Chip Camera Evaluation

[j1clark@ucsd.edu]

Can anyone explain to me, in some simple terms, what ' Film Latitude ' mean??

Film Film, negative film, has a 'dynamic range' of up to 12-14 stops, when density is measured on a densitometer. This means that an 'over exposure' is saveable, since output print paper (and I think this is true for movie film) has a range of only about 7 stops. So with development, and printing, one can still maintain detail in the highlight areas.

When this applied to things digital, the high end ARRI Alexa is reported to have a 14 stop dynamic range. The typical HD display has a range of 7 stops, so, one can again 'think' about 'latitude', and use some form of post processing to represent the camera image on the display device.

For low end cameras, the range for many seems to be in the 6-7 stops of dynamic range, the output HD display has a 6-7 stop range... leads to... no latitude...

I just saw that the Canon 1-D has a 'log' mode. Unfortunatley it is only 8-bits of representation, so will not give as high a dynamic range representation of the image, but it may give better than the linear 8-bits currently typical in lower end DSLR's.

Since I recall you are/have/may use the Red, you need to find out what it's sensor is capable of along with the data encodings, to estimate how much 'latitude' you have given the dynamic range of the camera, vs the display range of the output device.

Digital Cinema projectors may have a slightly larger dynamic range... but one again would have to research how much...

[Razz16mm]

Dynamic range is the maximum value range from peak white to black or noise floor that a medium can capture. Latitude is the range of exposure settings the photographer can use within the DR limits of the medium and still achieve acceptable image quality for intended purpose. Film stocks can capture around 14 stops of DR, but practical exposure latitude the photographer can work with is usually considered to be about +/- 2 stops around the film's base ISO rating.
Digital video is a bit more complex, depending on gain structure, noise reduction, and processing one may have 4 stops or more usable underexposure latitude, but you have little room for overexposure if you want to preserve film like highlights.

[j1clark@ucsd.edu]

Film stocks can capture around 14 stops of DR, but practical exposure latitude the photographer can work with is usually considered to be about +/- 2 stops around the film's base ISO rating.

Yeah, I forgot about 'how much underexposure can a film stock stand, with adjustment in development to compensate', before the image quality degrades... as a form of 'latitude'...

With digital, my 'problem' has typically been a too wide a contrast range of the scene, fitting into the 7 stops of what my camera can capture...

In the case of a scene that has 4-5 stops, increasing the gama of the image, will cause 'problems' in increasing the noise of the sensor, but obviously a 1 stop 'low exposure' can be boosted, all things equal... were as a 1 stop over is lost...

[Kenneth Lau]

If you take a look at the latitude chart from the Single Chip Camera Evaluation from 2011, you will see that film shows about 14 stops of exposure latitude, and the ARRI Alexa was the only video camera to match this latitude range.

2011 Single Chip Camera Evaluation

Thanks for explaining guys.

And this is a great site ! ! !

[Kenneth Lau]

Recently I have been shooting with the RED one and Epic and realize that when shooting a subject close by the window, it is really hard to have whatever outside properly expose in a sunny day. Even I stop it down to like F.12, outside is still blown out a little bit. If I stop it down more, everything goes to black. Does this has to do with the limitation of they latitude ??

[TheDingo]

it is really hard to have whatever outside properly expose in a sunny day

...Simple shot: Correctly expose for the outside, then add enough lighting inside to properly expose your subject by the window. The trick is to make your indoor lighting look "natural", which will take some practice to get it right.

[starcentral]

Like what many others have already said, outside of how many "stops" film can capture (ie. 12-14) on a black to white scale one thing about film is its ability to be pushed or pulled in post by several stops if needed.

Remember every stop doubles or halves your ASA film stock rating, so if you shoot 2 stops under exposed, you quadruple your film stock ISO. ie. 200 ISO goes to being effectively 800 ISO.

Pushing "digital" works best with RAW, uncompressed, or higher bit-rate and color sampled footage before you start to get artifacting and noise monsters.