Digital Workflow - Part 1

Adobe Bridge
 This is the first tutorial in a series that will show you how to apply the proper techniques to convert RAW images to JPG images and enhancing them properly. If your camera supports RAW images, it is highly recommended to use them, but you can use most of the techniques described here with JPG images as well. Below is a list of most obvious advantages of RAW photography:
  • Higher Dynamic Range - The Canon 20D records images with 12-bit Dynamic Range while the JPG file format only supports 8-bit. This means you get 4-bit more information, which is 16 times more levels. This will come in handy for those images that have a high dynamic range (shadows and highlights) or if you are trying to boost local contrast (more about this in the next part of the tutorial.
  • The sensor of most digital cameras does not record color information (the exception is the Sensor from Foveon that is being  used in the SLR by Sigma. Most sensors have a matrix of color filters that filter out certain wavelengths. The color information for each pixel is then interpolated from this matix. In order to prevent aliasing, an anti aliasing filter is being used, which impacts the sharpness. To make a long story short, the images always require sharpening and if you do the processing on your computer instead of relying on the camera default settings you can do a better job.
  • White Balance can be adjusted later (remember, no color information is recorded in the RAW file)
  • You can use curves for local contrast enhancement during the raw conversion process

Adobe Bridge Metadata View

I will show you how to tackle the RAW conversion in the next part of the Workflow Tutorial. In this part I will talk about Adobe Bridge, that ships with Adobe Photoshop. I use Photoshop for all steps of the process, since I find it the best tool available on the market today for this task. You can also get Adobe Photoshop Elements if  you find that the price is too steep for the full version. However it is such a vital and integral part of "making" photos, that I think it is almost as important as choosing the right camera for the job.

After downloading all the images into a folder, you will want to see what you got. The color management on a windows computer is not implemented really well, but the Adobe Photoshop will take care of this. Assuming that your monitor is calibrated (later tutorial) you will want to view the images with a programm that makes use of this calibration data. Alternatively Adobe Gamma (ships with Photoshop) will give you some rough calibration. This is important to remember, since you will otherwise make adjustments based on false information! Adbobe Photoshop ships with an excellent Image Browser for this task, Adobe Bridge. Bridge will show your images using calibration data!

Adobe Bridge File Navigator View
 The first 3 pictures on this page show 3 of the many possible ways to configure the view of Adobe Bridge. I usually prefer to work in the Lightroom View (first on this page) with the size of the thumbnails blown up a little bit. This way I can easily judge the pictures and see which ones warrant closer attention. There is a number of preset workspaces (Window -> Workspace) for some of the most common tasks. The second picture shows the Metadata View Plane. Here you can view the EXIF information that your camera recorded and you can enter more data (description of the image ...). Sometimes I take several different shots of a scene and with the Lightroom view I can easily compare them and choose which ones I want to process further. You can start Phtoshop or Adobe Camera RAW from Bridge and you can perform basic operations like rotation. Most important to me are the sorting functions.

You can label pictures and you can rate pictures. In the example above, I am about to label some of the pictures and tell the software that those are parts of a larger panoramic file. In order to do this, I simply give it the label Panorama (a label I defined ealier). I can then instruct the software to show only images that have been labeled as Panoramas or not to show them. Since these files usually take a lot of time to process into a large panorma (Ultra High Resolution Tutorial), I will take care of them later.

Additionally I can give pictures a star rating by clicking on any of the dots below the thumbnails (dot 1 through 5 equals 1 to 5 stars). You can always label and star more than just one image by selecting multiple images (see picture above).

In this image you can see that I labeled a subset of Images as Panorama and I gave them a 4-star rating. I can now sort all my images by star rating, to process those high quality images first.  You can also play a slideshow with Adobe Bridge. The tool understands all Adobe Formats (including PDF, Adobe Illustrator ...) all Image formats and a variety of other file formats. It is more than just an Image browser but thats what I use it for most of the time, because quite franky Adobe Bridge is somewhat slow. It requires some processing power, which is not surprising, considering that each of those CR2 images need to be converted somehow for display. Once you make adjustments in Adobe Camera RAW (next tutorial), you will see the thumbnails in Bridge update to reflect those adjustments. Fortunately, none of those are destructive. They are saved in a seperate file.

Bridge is probably one of those applications least understood. The power and flexibility is immense. You can easily take a series of images and combine them into an animated gif. Quite frankly I haven't fully grasped the full functionality, even though I have been working with it for quite a while now.

Dynamic Range of RAW

I think it's misleading to say that RAW has more dynamic range than JPEG just because it has more bits. More bits just increases the resolution, not the range. Dynamic range is a function of the sensor, not the encoding.

It seems most DSLR cameras today have a dynamic range of about 8EV (or 8 "stops"). For details (and references) see my page on photo editing and RAW vs JPEG.

Theoretically, the dynamic range of any sensor is infinite since it doesn't matter how negative n goes in 2^n, the value will always be non-zero and thus you could argue that you have "n" stops of dynamic range.

Practically, however, your dynamic range is limited by the amount of noise on the sensor. As soon as noice exceeds your signal, you must stop counting. A cheap point-and-shoot camera may have only 5 stops of dynamic range while a good DLSR has 8 or so. This is irrespective of the number of bits they use to represent the signal. Because of its "shoulder", film has about 12 stops worth of dynamic range, much more than digital.

What RAW does allow is expansion of part of the captured dynamic range without posterization, thus allowing detail to be brought out of shadow and highlight that would be cut off if the data was limited to fewer bits.

Thanks for the feedback

Thanks for the feedback Brian. I am not sure if you know this, but when the image is processed inside the camera, it is mapped to the 8-bit range. This also results in clipping in the shadows and highlights, hence the loss of dynamic range. I think I mentioned in another part of this tutorial series, how I am able to pull more detail out of the highlights, because my Camera actually records more of the highlights (not visible unless adjusted and defenitely clipped away for JPG). I think I understand your standpoint. Generally Dynamic Range is not the same as Resolution, but consider this: When I am working in the shadows (lets say the lower 1/64th of the range), 8-bit resolution only gives me 4 levels to work with. 12-bit gives me 64 levels. This means I can also pull more detail out of the shadows, that would be mapped to full black in JPG. Hence it appears to have more dynamic range. As for the infinite dynamic range: The signal acquisition system is limited by the ADC and the Preamplifier. If the resolution of the ADC is 12-bit, this will also determine your maximum dynamic range (roughly 1/(2^12)). Usually this value is chosen to be about the same as the noise floor (otherwise one could easily increase resolution). A higher ISO setting requires a higher gain for the preamp, hence a higher noise floor (the noise gets amplified too). This is the main reason for more noise in higher ISO images. So what does it tell us? There are many factors determining Dynamic Range. Quantization Errors (ADC resolution), Noise (Sensor Size), Preamplifier noise (LNA design) ... Together they all determine the dynamic range. But resolution is one part of the equation. If you map your image into a 8-bit color space, you will defenitely increase your quantization error and hence reduce your dynamic range. Quoting from this wikipedia article: For example, a 12-bit digital sensor or converter can only provide a dynamic range in which the ratio of the maximum measured value to the minimum measured value is limited to 4096-to-1. Yes I know, my tutorials are not very scientific. They are targetted for the enthusiastic photographer rather than the tech wizard. Thanks again for your feedback

Dynamic Range

"8-bit resolution only gives me 4 levels to work with. 12-bit gives me 64 levels"

Right, and that's what I mean when I said you could expand a given range and still see full detail.

"The signal acquisition system is limited by the ADC and the Preamplifier. If the resolution of the ADC is 12-bit, this will also determine your maximum dynamic range (roughly 1/(2^12))"

In an absolute sense, that is true. However, that assumes that the value 128 is exactly twice as bright as 64. This does not have to be the case though, in general, it is. I could use those same bits differently to achive a much higher dynamic range, though will less detail. The Nikon "Compressed NEF" does just this for holding the original 12 (linear) bits of data in 10 bits.

My point is simply that the ability to get more detail by scaling the low end doesn't help you if it's mostly noise anyway and scaling the upper end isn't so much increasing the dynamic range of the image as it is changing the mapping of the input to the output.

An 8-bit image where the input/output ("levels") curve is not a straight line must interpolate where the slope is steeper while real information can be used if more bits are available.

Still, the dynamic range of what was captured (the brightest to the dimmest) is increased by having more bits only if the sensor provides more than 250:1 contrast. According to the "dpreview" reference I give in my article, modern cameras like the Nikon D80/D200 and the Canon D30 can't really do this.

Allright, I acknowledge not

Allright, I acknowledge not having written the most technical explaination. Good call.
However I will still maintain that a straight mapping of 12-bit data to 8-bit data will always increase the quantization noise floor and hence reduce dynamic range.
You are right again, when you say that the Sensor is a Linear Device, while image processing is a nonlinear process. Hence the loss is not exactly equal to the loss in bit scale (thats what I am reading from your Compressed NEF paragraph).
Lets just agree on the simple fact that the RAW image does contain more data and that an experienced user can use that extra data to perform image enhancements vs. the generalized processing the camera performs.
I didn't know that article about the contrast, but it goes hand in hand that it is always the weakest link that determines performance. The ADC resolution is always chosen so it won't increase the noise. Higher resolution also means more power consumption (shorter battery lifetime).
Again, thanks for pointing out the finer technical details. I appreciate your feedback.
How is that D80 working for you?

My D80

(didn't notice that last line when I last looked)

I'm enjoying my D80. Compared to my F90X, I like that I can just shoot away for no cost. Just hold the button for two seconds and I've got six frames from which to choose the best. I can shoot indoors with ISO800 or even 1600 and still get good images. With film, I almost never shot above 400. On the other hand, it doesn't have the "shoulder" of film and thus burns out easily if I'm shooting a sunset.

So far, my experience is that digital gives you a better chance of capturing the picture you want, but film does a better capture.

DPI default settings?

I have Adobe 7.0 and have read in several places that if I click on the 'help' icon in Adobe I will find a 'wizard' choice - I find no such wizard.

My problem is - no matter how large the photo in my camera is - I seem to only be able to get 180 DPI.

A magazine is interested in my photos - but requires 300, as most publications do.

can you help?


You don't have to change this setting.
Simply go to Image -> Image Size ...
Turn off the Resample option and then change the DPI to 300.
It is just a number, that has nothing to do with resolution:
An image of 1200 pixels wide will be 4 inches at 300 dpi or 8 inches at 150 dpi. When you turn of the Resampling, the 1200 resolution will be retained (thus the quality does not change) but the DPI number will be updated.
That should do it.

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If the resolution of the ADC is 12-bit, this will also determine your maximum dynamic range slot machine gratis