Why We Should Care About Bit Depth

Bit-Depth ChartI see lots of questions about image bit depth, specifically about what is the “right” number of bits to use when capturing, editing and printing. And frankly, as far as I am concerned there is no one size fits all answer to this question.  As a general rule I like to use the largest color space possible (most number of bits), which means shooting Raw with loss less compression (12 or 14-bits in most cases), editing in 32-bit color spaces and printing/digital display in 8-bit.  In some ways Lightroom has made this easier on photographers by eliminating those questions of color space and using a 32-bit color space by default, then exporting to 8-bit.

To give you an idea why we, as photographers, should care about bit depth and always use the largest color space available I created this dramatization at the right.  This shows a gradient from pure black to pure red at varying numbers of bits.  The left column is 1-bit, where there are only two possible values.  Next to that is 2-bits, where 4 (22) colors are possible.  Next to that is 4-bits, where 16 (42) colors are possible, followed by 8-bits, where 256 (82) colors are possible.

The problem comes when you change an image from 8-bits to 4-bits, you get only 16 colors.  The 256 colors can never be recovered.  No matter how many adjustments, using whatever tools, you can never get those smooth gradations of color back into the image, and as you apply strong adjustments on an image that has been reduced, those smooth gradients turn into stronger contrasts.

Strong Levels AdjustmentIn this image, I took the upper half of the 4-bit color and applied an exceptionally strong levels adjustment, moving the black point to 127.  Rather than smoothly adjusting the color into 16 hues again, you get only 8 hues, just with stronger differences between each of the bands of color.

So if we ultimately print in 8-bit color spaces, why do we bother capturing and editing in larger color spaces?  Because capturing and editing in these large color spaces allows us to maintain the smoothest color transitions possible up until the final output.

It doesn’t really matter if you understand the science (or really mathematics) behind why to choose a specific color space, as long as you understand that using the largest available color space at each step will produce the best results, and that it is best to save a copy of the image in the larger color spaces as your “master” file, since it contains the most detailed information about the image.

Tim Grey

Tim Grey is responsible for accelerating my grasp of Photoshop.  He does a good job of identifying common issues that people have with photo processing in Adobe’s applications and writing well thought out answers to address the problems.  His Digital Darkroom Quarterly (now called Pixology) and his Ask Tim Grey newsletter provide easy to understand answers to questions you might not have even thought to ask.

Tim is an expert in Photoshop and Lightroom, with extremely good access to Adobe for questions that involve “why does this Photoshop filter work this way?”  He is also a published author, with several books on color management and digital darkroom workflow, including both Photoshop and Lightroom workflows.

Scott Kelby

kelbytraining_titlelogoScott Kelby is quite the entrepreneur.  He turned a graphic arts business into a multi-million dollar per year enterprise, largely by working closely with Adobe to develop extensive training videos on nearly all aspects of photography and Adobe’s products all available at Kelby Training.

He also created the National Association of Photoshop Professionals, a professional organization of graphic designers and photographers where people share tips and effects that can be accomplished with Photoshop and its associated Creative Suite applications.

I initially purchased a few of the Kelby Training videos on DVD, which I loaned throughout my camera club for a couple of years.  This was shortly after Photoshop CS4 was released, and the CS3 videos all went on sale for 1/2 price.  But they convinced me that the video training would work for me, and that I had a tremendous amount still to learn.  For a couple of years I used their online training videos.  At $200 per year, it was about what I expected to pay for a 2 day seminar with no personal interaction.  This gave me access to the hundreds of videos that Kelby Training offers, 24 hours a day, 365 days a year.  Over those couple of years I learned a great deal about Photoshop, Camera Raw and Lightroom, as well as watching numerous photography oriented videos from people like Joe McNally, Frank Doorhof and Jay Maisel.

I have also read a number of Scott Kelby’s books, however I found them to be somewhat trivial for my taste.  Everything that I have read by Scott is a cookbook photography methodology.  That is, you are given a recipe of such and such a lens, at such aperture and exposure.  If you have a reasonable grasp of exposure, depth of field and focus I believe that you will find them too basic as well.

But give the Kelby Training site a spin, I think that you will find at least something that piques your fancy.

NVPS Competition Upload Preset

This Lightroom Export preset will export images at the best resolution for a 1400 x 1050 projector.  It applies “Screen” sharpening to the image as it exports.

Use NVPS Competition Preset

We have saved a Lightroom Export preset that automatically configures settings for NVPS competitions. This should simplify the process of defining all of the correct export settings. You can download this preset at NVPS Competition.lrtemplate.

Installing the LR Export Preset

After downloading the NVPS Competition.lrtemplate file, copy the file to the following directory based on your operating system

  • Windows XP: C:\Documents and Settings\username\Application Data\Adobe\Lightroom\Export Presets\User Presets
  • Windows Vista: C:\Users\username\AppData\Roaming\Adobe\Lightroom\Export Presets\User Presets
  • Mac OS X: /Library/Application Support/Adobe/Lightroom/Export Presets/User Presets

Applying the LR Export Preset

Select the image(s) to be resized, then select File, and Export. When the Export dialog opens, select NVPS Competition under User Presets in the Preset section of the Export dialog. This will automatically apply the appropriate competition settings.Press the Export button and a Windows Explorer window (or Finder window on the Mac) should open with the resized images in it.