The histogram can be a very useful tool in helping photographers properly expose their images, but it can be just as hurtful as it is helpful when used improperly. Cinematographer Ryan E. Walters explains why the methods used by photographers to expose their images should not be used by videographers.
ETTR (Expose To The Right) is a common practice to obtain the most dynamic range in a shot. In theory, it provides cleaner images with less noise in the shadows. On the flip side, ETTR can lead to accidental overexposure and unrecoverable highlights. The most common issue with histograms is that they are horribly inconsistent; the look for one shot may not match that of the other.
Histograms are vague – the waveform monitor is a better tool for video. Whereas the histogram only shows one value (luminance), the waveform monitor gives you a distribution of brightness from bottom to top. It matches vertical sampling, so you see a representation of the frame left-to-right. It’s also far easier to match shots to other shots in terms of brightness with the waveform in comparison to the histogram.
You can’t tell how bright someone’s face is by glancing at a histogram, but you can certainly do so in most situations with a waveform monitor. Sure you can get an idea of average contrast and glaring exposure problems, but a waveform monitor is like a microscope analyzing every detail.
In my opinion, histograms should always be used (if at all) alongside other exposure tools like the vectorscope, RGB Parade, zebras and false color displays. Non-linear editors like Adobe Premiere seem to have this belief too, as they have easy access to these tools where histograms are buried in menus.
Histograms are a good tool to see if your blacks are crushed or your highlight are blown, but should not be the be all end all method of exposing your image. If you rely on the histogram alone, you might you might have some difficulty when it comes time to color grade.
[Via NoFilmSchool / Images Screen Caps]
Do you use histograms for every shot? Should histograms not be used in photography as well as cinematography? Let us know what you think?