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Thursday, July 12, 2012

A misleading statement 30 000 image database.

I have 'issues' with a statement about Nikon's matrix metering . Many people believe that matrix metering compares each image with a database of 30 000 images "stored in the camera" . I don't believe this is accurate .
Here is their statement
Matrix Meter is called the 3D RGB Color Matrix Meter. 
This meter gathers information from 1005 red, green, and blue sensors and factors in distance information provided by the lens as it evaluates proper exposure calculation. This meter instantly analyzes a scene’s overall brightness, contrast, and other lighting characteristics, comparing what is sees against an onboard database of over 30,000 images for unsurpassed exposure accuracy, even in the most challenging photographic situations. By the time the 3D Matrix meter has made its considerations of colors by hue and saturation, tonal ranges by brightest and darkest, areas of similar tonality that are connected or separated, distance to the subject, and compared that to its database generated from photographic images, it’s got a very good idea of what the exposure should be.

If you are a beginner, Matrix is where you should start. As your skills grow, and they will, you will acquire a better understand of when it might be beneficial to use other light metering options.

What is the database of over 30,000 images?
Over the years Nikon has studied the color, area of coverage, focus distance, contrast, size and shape of shadows and highlights and exposure characteristics of over 30,000 actual photographic images and incorporated this data as a reference source for the expert exposure system that is the 3D Color Matrix Meter."




I find this statement particularly unbelievable considering the difference we see in matrix metering in different bodies . My D40 meters very strongly for the focus point selected , the D90 is more accurate and I shoot in matrix metering with both of them .
Think about it, when a D4 is shooting at 10 frames per second is it really likely that in less than a tenth of a second the camera's processor can do all its calculations including flipping through 30 000 images before taking each picture ? Close to impossible I say !
It is more likely that Nikon have studied 30 000 images and written an algorithm based on that research to program matrix metering . There are many other factors involved in calculating exposure and each body is slightly different with different parameters programmed into it otherwise a D40 would give the same exposure as a D4 with the same scene - but this does not happen .
So my next lot of studies will involve analyzing matrix metering to see if I can work out the metering parameters of the D90 - I'm sure it will be similar to many other models out there and the more I understand a program the more benefit I can get from shooting in that mode by being able to 'predict' its reaction to different scenes at different distances.

4 comments:

  1. How much space do you think 30k histograms uses? That is all a picture really is to a light meter, so the database doesn't need to store the whole pic. Since the light meter only works in increments of 1/3 - 1/2 EV, that database can probably be organized, de-duplicated and indexed for better efficiency.

    There's probably more going on with Auto-WB than there is in metering.

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    Replies
    1. They state that it is 30 000 images , not histograms. For this to be even remotely true it would have to be at least an image with as many pixels as the metering system uses along with colors , distance info [ difference between a photo of a painting and an actual photo with bright sky in it in the distance] . 30 000 histograms would be totally meaningless on their own.

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  2. "3D" means distance info " color" means more than a plain histogram " matrix metering" means divided into segments.
    Histograms can at least have color information - not distance or segments which is what Nikon's matrix metering is all about.

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