tech:photo Archives

October 17, 2007

Black & White in CS3

cs3 channelmixer 1

Using Photoshop to create greyscale images from full colour ones just got even better using the new channel mixer in CS3.

There are several way to do this, and the channel mixer has always offered the most control. Now in CS3, it offers some very interesting pre-sets as well. All based around traditional b&w film & coloured filters. This image shows the dialog box accessed by the menu-bar, image>adjustments>channel mixer.

The presets drop-down menu at the top allows you to choose between several predetermined spectral responses and creating your own custom set of values.

cs3 channelmixer 3
  • Infrared
  • Blue Filter
  • Red Filter
  • Orange Filter
  • Green Filter
  • Yellow Filter

Use of these kinds of filters have had a long history in b&w, photography. Panchromatic film in itself has only been a reality in photography since the 70's. Prior to this b&w film was more Orthochromatic ie sensitive to the blue and green but not the red end of the spectrum, this is why so many photographs from the early history of photography had washed out skies, and also saw many many smart photographers take 2 exposures, one for the foreground and one for the sky, from the same camera position, then in the darkroom simply sandwiching the 2 negatives together to produce a print. Others simply, kept a collection of skies on hand in the darkroom and used as needed.

Now CS3 enables you to mimic the effects that these filters have in how colours are represented in a black and white print. Yellow for example it is said most closely mimics the world the way we see it and of course Red filters produce dramatic skies, while colours like green and blue can be used quite effectively in the right situation.

When working traditionally the colour of the filter you used with block it's opposites and passed more of it's own colour. So for example when using a Red filter less Green and blue light strikes the film than red. Red objects reflect more red light creating a denser negative, producing a lighter print. Where as less blue and green light strikes the film making for a less dense neg and a darker print.

I can only wonder now at the demise of silver gelatin printing. As anyone, armed today with a modern DSLR, and a good A3 ink-jet printer can easily produce some wonderful prints using these technologies.

the real question is though is there a measurable qualitative difference between the two output methods, personally I still see differences in Silver Gelatin prints over ink-jet ones, but after 20 plus years of working with the medium I've come to appreciate some unique and subtle qualities that I've yet to see in ink-jet prints.

I may, in an upcoming article, show the differences between the pre-sets at least.

Another approach on Luminous Landscape

October 18, 2007

Black & White

Here's 2 samples of the presets I was talking about previously, including the original file

First the original.


Next, the Yellow Filter pre-set.


Finally the blue filter preset.


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April 13, 2008

Photography techniques:

Exposure times, aperture settings and film speed… or; everything in photography is a trade off.

[From Photography techniques: Exposure times, aperture settings and film speed]

June 9, 2008

Everything in Photography is a tradeoff

This article on Luminous landscape, is, I guess typical. In that lot's of quasi-scientific posturing is made about testing. Perhaps the target audience appreciates this. I personally think it is over complicated.

[From Some Noise About Noise]

The final paragraph says it all though for me, and given my understanding about noise in a digital file and how it is created, actually defeats the intention of the article.

My advice on avoiding noise, in digital files? Expose correctly and never ramp up your ISO settings, unless you are absolutely stuck. This necessitates the carrying of a tripod, something I've done for 20+ years, and unless I'm prepared to shoot wide open, unavoidable. Don't want to carry a tripod, shoot wide open or settle for other technical trade-offs like noise.

Edit, 2008.06.10

Throughout the whole article the tester neglects to mention one key and pivotal piece of information. How many stops exposure difference between the brightest area in the scene and the darkest. Expoxures choices are driven by this more than any other, for example how little detail can I accept in the shadows, hw will that impact on the highlights. Can I keep detail in the highlights, without having empty black shadows? As an aestheitc choice, do I want either? Adding insult to injury, to the best of my knowledge CCD's can only record 3 1/2 stops. In Australia this potentially makes photography impossible, on sunny days, the time when most amateurs go out to take photographs.

June 14, 2008

Photoshop Sharpening

All digital files, jpeg, or raw require some level of post processing, to achieve film like appearance. this technique is a combination of Smart Objects and the High Pass Filter*. A word of advice, I have NOT used this technique on a print, only screen images, which require different approaches I'm told.

First process your image in your favourite raw processor. Next, duplicate the background layer twice. Now, convert each layer to a smart object. On the top layer, apply the high pass filter at a setting of about 30-50. On the next layer, convert the image to b&w, using black and white converter in image>adjustments. Apply the high pass filter again, this time however, at a much lower setting, say around 1.5 to 3. Now change the layer blending mode to soft light on all layers above the original background layer. hey presto a crisp image with the kind of acutance we've become accustomed to from our years of film use.

The original image


The finished image.

photoshop sharpening
Uploaded with plasq's Skitch!

*This technique requires Photoshop CS3, Kent Johnson first showed me this idea, I've tweaked it slightly, as I'm sure others will have.

Less is more, as always, be careful, not to go too far overboard with the sliders, but if you do if you've used smart objects you can edit the setting at a later date, on the un-flattened file. So even without CS3, you can simply apply the high pass filter to the image directly, and the results will be the same, but you won't have the infinite undo-ablitiy that the smart objects allow.

January 2, 2009

What's the point?

Recently discovered this filter/plugin for photoshop, that adds film grain to a digital file. From where I sit if you want film grain use film, sheesh?

film filter
Uploaded with plasq's Skitch!

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