Category Archives: measurbation

equivalence is more equal than you think

There is a perpetual online discussion amongst measurbators about “equivalence”.


Equivalence is a very real phenomenon which can be predicted and measured.  The idea is that when comparing cameras with different sensor sizes, smaller sensors tend to have greater depth of field at “equivalent” focal lengths.


Why “equivalent” focal lengths?  Ok, it gets technical pretty quick, but rather than bore you with esoteric technobabble, lets just look at some images.  (Photography is about making images, right?!)  If you feel that the differences are drastic, then by all means read on.  But if none of these images strike you as dramatically different from one another, just know that you can safely ignore anybody who ever mentions “equivalence” or “equivalent apertures”.  Because they’re either trying to waste your time or sell you something.  (hopefully I’ll have saved you from the clutches of some forum troll)


Here they are:




This is what the war is about.  A mountain of a mole hill, idn’t it?

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D7100 practical bit-depth

More test results from this past week.  I already know that 14-bit isn’t any better than 12-bit at base ISO on the D700.  Well, let’s just make sure things haven’t changed with new gear.

There is (quite wisely) no “uncompressed” raw on the D7100.  But if you’re foolish enough to want to waste space, there are “losslessly compressed” and “compressed” modes, in addition to being able to select between 12 and 14 bit files.  My preference is the smallest file, since that helps the buffer dump to the card faster.  Lets see if I lose anything choosing 12-bit compressed (allegedly lossy) vs 14-bit lossless, first just comparing the overall scene before manipulation:


There’s a pretty good hot spot in between those trees.  Let’s dial down the exposure and see if one setting is capturing more in the highlights:

12 bit lossy14-bit lossless

Can you tell the difference?  There’s no posterization.  Now you can complain that the highlights didn’t blow, however, the point is that even in the 12-bit lossy version, there’s more highlight than I need.  Unless you’re doing something wrong, you probably don’t need 14-bit for highlights with the D7100.

Now let’s look at the shadows (artificially pulled up in post):


Not seeing anything different here.

Now the point is not that there’s no difference.  The point is that for actual real world shooting, there is no appreciable difference.  Don’t waste your time or card space on 14-bit files.  If the review sites were smarter or more honest, they’d tell you the same.

Of course, if you want to come up with a reproducible test with real world repercussions, please, by all means do so.  And share your results like I have!

Here’s my original raw files if you want to play with them yourself.

Bit Depth Part 2 of 3

(or: Proving what I already knew)

In the last post we looked at what bit-depth means and how it is theoretically useful.  It could theoretically be useful for recovering detail and tonal nuances that don’t appear obvious from standard processing.  The example I gave was to illustrate how under extreme settings we could add contrast to enhance the appearance of an edge between two nearly similar colors (two nearly identical shades of green).

Theoretically, a file with more bit depth has more information and if manipulated, we might be able to use that information in useful ways.

So, let’s take a look at this from a capture standpoint.  Pedal, meet my dear friend, Metal

one of the images at default settings

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