Digital B&W - Accuracy and workflow questions

[luis_bascones]

I am shooting pretty much hundred percent digital these days, but I

am developing a deeper and deeper interest in B&W photography.

Consequently, I am trying to learn about B&W digital photography, and

corresponding digital darkroom, and I can�t say that the information

I have found so far is very good. I understand that I have a large

handicap of not ever having developed and printed my own photos, so

the whole task seems to be incredible daunting because of parallels

and anti-parallels between digital and traditional photography.

 

Below are some ruminations on the issues I have been thinking about,

plus some questions (and maybe opinions) that I have.

 

The digital equivalent of the negative is the sensor itself. Assuming

that we are working with raw images, we are basically obtaining three

images at the same time, each through a specific filter (green, blue,

and red). If the format is raw, then we have the information before

it is combined into a single image (using the famous Bayer

algorithm). Theoretically, my D100 is capable of capturing 12 bits of

information per each raw pixel/sensor, so, in its rawest of forms, I

have a dynamic range of 12 stops of light captured in the file, which

is potentially great as it would allow me to pull out detail

when �printing�, or correct exposure mistakes.

 

Given that I have 12 stops on �film�, and assuming I�m trying to use

the zone system, this would mean that either each zone would be about

1.2 stops from the next.

 

Q1 � Is this the right way of thinking of a digital version of the

negative in the zone system?

 

But this is a noise-free scenario that is not very realistic. In the

real world I will most likely want to sharpen the image, which is

inevitably a noise enhancing process. Also, having a non-infinite

signal-to-noise ratio becomes more and more obvious as I increase the

gain (ISO) on the sensor.

 

The next issue that comes to mind has to do with image capture. The

standard option is to capture the lightness (value) of the image as

accurately as possible. We typically do this by looking for an area

of known gray level, metering off it, and compensating if necessary.

This may not be necessarily the best option as it may keep us from

taking advantage of the complete dynamic range of the sensor.

Theoretically, I should want to center exposure of the image in such

a way that I keep highlights and shadow with enough detail and this

may mean that mid-gray would end up elsewhere in the sensor scale of

values (i.e. in a scene where the lowest brightness level

corresponds to mid-gray. In this case I would want mid-gray to end up

lower than in the middle of my sensor�s dynamic range). To be able to

take advantage of the sensor�s whole dynamic range, one would have to

find the range of the scene (finding the number of stops of the

scene) and then adjusting the ISO setting of the camera to �fill� the

range of the sensor while keeping in mind the effect it will have on

the noise. This brings me to the next question.

 

Q2 - Is the ISO setting of the camera a simple gain control?

 

If so, both signal and noise would get amplified, and therefore

nothing would be gained in terms of signal to noise ratio. If that�s

the case, then adjusting the ISO for static images is meaningless and

should only be used to be able to capture moving subjects in low-

light conditions.

 

BTW, one problem that comes to mind with this approach to using the

full dynamic range is that the �true� levels of gray will be lost,

and must somehow get captures via notes or a second image that

contains the �true� gray levels.

 

The next step is taking all the information capture by the camera

(raw format), and controlling the way it is transformed into a

grayscale image. Many people simply desaturate the color image and

that�s that. But for a higher level of control, one would prefer to

use the equivalent of the channel mixer in order to achieve the

desired effect (color filters, etc) while minimizing loss of

information. If the raw image has 12 bits of data per channel

(color), one would prefer to mix these channels at 12 bits, and then

control the way it�s downsampled to 8-bits so as to reduce its

impact.

 

Q3 - Can the human eye see more than 256 levels of gray/What is the

dynamic range of the human eye?

 

Q4 - Is there a way to avoid downsampling and keeping 12 bits of

information and still do some minor retouching/adjusting of the

image?

 

Q5 - Is there any digital printing process (piezography?) having a

dynamic range of 8 (or 12) stops?

 

As you can see, I have quite a few questions on how to optimize the

workflow and picture quality in the digital darkroom. Most of the

questions I have to with B&W, but they easily extend to color. Does

anyone have answers to these questions, or know of a good book that

covers all these topics? Am I looking at this the completely wrong

way?

 

Thanks a bunch,

 

-LuisB

 

[ellis_vener_photography]

1.) well sort of.<P>

 

2.) yes<P>

 

3.) yes. evidently the average human visual processing system sees about 512 levels

of color or grey -- or about 9 bits.<P>

 

4.) use photoshopCS and work in 16 bits. the problem is the output, I don't know of

any printers that are set up for more than 8 bits.<P>

 

5.) don't know<P>

 

Book recommendations: "Real World Adobe Photoshop 7" , "Real World Color

Management" or <A href = http://www.amazon.com/exec/obidos/tg/detail/-/

0321130103/ref=lpr_g_1/102-2249750-1294517?v=glance&s=books> Adobe

Photoshop Master Class: John Paul Caponigro, Second Edition </a>

[navarra]

I use almost 100% digital as well, and I am interested in B&W as well. I can't give you answers for sure, so I won't even try. I only want to say that after using different methods of convertion from a color digital image to a B&W one I still have the feeling that I am missing something in the final result and that it would be better to use a film camera for the best B&W quality.

 

I have a lot of images converted to B&W taken with my 300d, and some of them look great, but I still wonder how would them compare if placed side to side with a Tri-x (or similar) print. Maybe it's just me, maybe they are even better because there is almost no noise if a low iso is used, but still I'm waiting for an "official" article or publication to show me that yes, digital B&W gives results at least comparable to those of film.

 

Simone

[christian_dupuis1]

I don't want to wander too much off topic, but if you want to take a look at some

fairly neat Photoshop plug-ins that will emulate the grain and contrast caracteristics

of your favorite "analog" film, you can take a look at SilverOxide's product at http://

www.silveroxide.com and see whether that gives you a more pleasing B&W

conversion.

 

I used to shoot B&W TIFFs with a Nikon D1, but output on a generic color inkjet was

kind of disappointing. I'm still evaluating whether I'll convert an inkjet printer and

turn it into a B&W printer. The Piezography BW system is really interesting for that

type of work (see http://www.piezography.com ). Too bad that system doesn't fit my

old Stylus Photo EX; I'd love to turn that beast into a tabloid B&W printer.

 

Chris D.