Piezography Chronicles

Transcription

1 Piezography and the Black Point The black point of a digital image is the tone level at which black begins to have a visual meaning. However, it can also be where solid black is, or where solid black should be. This is of course dependent upon the context of using a black point. If the photographer is trying to imitate platinum printing, a black point could actually be at a tone level that is quite gray in comparison to a silver print because the dmax of a traditional platinum print is not as deep as a silver print. A photographer can decide to leave his shadows open with detail, or close them and make the entire range of detail into a solid black mass. In these cases, black point has a visual meaning. If an image is made using a digital camera or from a scan, there must exist a tone point at which the darkest matter of the image is recorded as the black point. Although if a dark enough subject matter is missing from the subject, a black point may only be theoretical. Finally, the tonal point at which true black is recorded may or may not be where the photographer visualized it. dmax = Black point. Black point or = dmax. The former objective, the latter subjective. I am not a big fan of using the Levels tool, but it behaves as a visual histogram of an image and is the most useful tool for visualization of the Black Point of an image file. The correction of this Black Point probably should not take place solely with the Levels tool, if the photographer desires the best possible print using Piezography inks and profiles. So I will provide a tutorial in this chronicle to demonstrate. Before we begin this tutorial, the most important consideration you should make is what black means to you. If you want to make images of incredible breathtaking dmax and contrast (which necessarily will lack the most incredible breathtaking shadow fidelity and fine tonal control (these two goals are not mutually inclusive today), you should probably make those incredible breathtaking dmax, contrasty prints with a color ink solution such as K3. Piezography is about the finest possible tonal control and about all the grays between black and white. However, if you would like to control and improve the presentation of dmax with Piezography read on!

2 dmax The darkest possible tonal measurement of a print is its dmax. With Piezography inks it is very rare to measure more than 1.8 on today s modern inkjet papers. This particular Piezography black that produces such a dark dmax is called Piezography Portfolio Black. It is intended for very short-term exhibition or for long-term presentation in portfolios. It is the only non-100% pigment ink in the Piezography brand of inks. Every other Piezography ink is pure 100% pigment, either from carbon, or a modified carbon pigment. Modification of carbon using the techniques of Piezography chemistry produces an even longer lasting ink than unmodified carbon (warm brownish black.) Carbon however, is only capable of producing a moderately dark dmax. A more traditional dmax measurement using a Piezography brand black such as Museum Black or the K7 black might not exceed 1.7, with measurements in the 1.5 to 1.68 being more prevalent. The reason we do not use dye in Piezography inks is because we wanted to make an ink to a much higher standard than is common today. By example, the fade conditions for the two most established institutes that give longevity ratings to inks, use an approximate 35% density loss as their accepted end point during the accelerated testing. In other words, if an OEM ink is rated at 90 years, it will have faded 35% density by then. Piezography inks are designed to fade less than 5% because that is the threshold at which the average human perceives fade. Therefore, because we have such a high standard, we do not create a black ink with an extremely high dmax. High dmax and high resistance to fade are not mutually inclusive. At the date of this writing we are testing the durability of a uniquely treated dye material that we are hoping to use to better current OEM carbon/dye mixtures. But it is our intent that Piezography be considered of historical longevity, because certainly color inkjet process cannot. Historical longevity needs to preserve the original intent of a photographer over the length of time so that subtly toned black and white prints do not only resist density loss, but also do not color fade when a color ink component can not match the longevity of the carbon component.

3 Finally, it might be of interest to see the amount of dye components that are present in OEM black inks used in the same printers that Piezography inks are used. According to EPSONʼs MSDS sheets for Ultrachrome K3 Matte Black, Ink Composition Carbon Black <3% Proprietary dyes and pigments <1% % by weight According to EPSONʼs MSDS sheets for Ultrachrome K3 Light Black, Ink Composition Carbon Black <2% Proprietary dyes and pigments <1% % by weight According to EPSONʼs MSDS sheets for Ultrachrome K3 Light Light Black, Ink Composition Carbon Black <1% Proprietary dyes and pigments <1% % by weight According to EPSONʼs MSDS sheets for Ultrachrome K3 Photo Black, Ink Composition Carbon Black <3% Proprietary dyes and pigments <5% % by weight According to EPSONʼs MSDS sheets for Ultrachrome K3 color inks, they are made up of a combination of Proprietary dyes and pigments.

4 Black Point as dmax If you are interested in a having a traditional black point that is the highest dmax in your print, this tutorial will be useful for establishing a good black. I write If you are interested, because some photographers have been responding to the capability of Piezography to render very linear tone so that if black and white are not occurring in their subject matter, they are feeling more inclined to not include them in the finished print. I went to a traditional school of contemporary photography and studied with Arnold Gassan who was a strong advocate of the Zone System and favored establishing a true black and a true white. I also though, do not force blacks when they are not within the tone range of the subject matter. This is mostly true if I am shooting landscape in inclement weather. But in this tutorial we are going to see where the black point is using the Levels Tool. We are also going to see how much black is actually present. Then we will use channel masking to increase or bring the black point to actual dmax black. Piezography only prints dmax black at pixels with a value of 0(L), which is same as 100%(d). The Levels tool uses Luminosity values from 0 to 255, while the Curves tool can be set to the same or density values from 0% to 100%. Illustration 1. A Grayscale images as seen through the Levels tool, and through the Histogram window.

5 In this example I have opened a typical digital camera capture that has been converted from color to grayscale without adjustments. The histogram is a mirror of the image. I have drawn red lines to show the corresponding histogram area for the highlight, midtone, and shadow. Illustration 2. The ocean waves that appear white are in the 10-15% range. There is no true black with a very small percentage of pixels even on the left side of the histogram. The image is actually exposed well, and there simply does not exist a true black or white in this natural subject that has been shot during a rainstorm with an extremely overcast sky. However, the print would benefit by an actual dmax black. I do not wish to artificially brighten the white top waves.

6 I can use the Levels tool to see the exact black point, in the image. Illustration 3. Levels tool is used to visualize the black point of the image. By pressing and holding the option (alt) key while clicking on the black point of the Levels tool, I can drag it to the right until I see a meaningful amount of black being previewed in the image. Everything else in the image is turned to white by this action. Were I to drag the black point further to the right (while simultaneously pressing and holding the option (alt) key) the black would increase to reflect the amount of pixels at that luminosity level. But, I am only trying to see where the darkest part of this image is. Photoshop books tell us that it is at the base of the mountain in Levels or Histogram. I ve gone considerably past that base. In fact, I am at Luminosity value 14 which in Piezography is not black. It corresponds to approximately 95% gray. Were I to print this image as is, there would be no dmax black.

7 My curiosity wants to see what is at the base of that mountain in the Levels or Histogram. Using the same technique produces a very narrow band of pixels that are near black (Luminosity value 4.) According to the histogram there are only 250 pixels of the darkest value in this image. This is certainly never going to be apparent in the finished print. What I prefer is the level 14 pixels from Illustration 3. What I want to do is make that range of pixels print as dmax. That level of pixels that I previewed includes pixel values lower than 14, but not higher. I do not want to do a simple Levels move of actually dragging the black point from 0 to 14 which would convert the pixels from 14 and lower to a value of 0. The reason I do not want to is because a Levels move would also adjust the tone of my ¾ tones and midtones. Levels works that way. Curves would make it easier, and a Mask would make it perfect. Illustration 4. Using the Levels tool to adjust the black point ruins the shadow detail. Compare to Ill. 2.

8 Using Curves is an improvement. However, in the illustration below the shadow detail is a little clumsy. I am looking for more finesse in my shadows, while still being able to print dmax. I want my black, but I am unwilling to give up shadow detail. So in the next example I will use a Masking technique through which to adjust my dmax. Illustration 5. Input value 14 will be converted to 0, and the rest of the image is protected with several points that act to prevent the ¾ tones and midtones from becoming darker or lighter.

9 Masking Technique Illustration 6. Using the Channels Window, Load channel as selection. (You should be working with a single channel grayscale.)

10 Illustration 7. On the Tool pallete, click on the Edit in Quick Mask icon or type (Q) key, a shortcut you may wish to learn as you use this technique frequently.

11 Illustration 8. Clicking off the Gray channel visibility will allow us to see the Quick Mask channel as a grayscale image rather than as a mask image. This will allow us to intuitively edit it to make a perfect mask for our black point.

12 The perfect mask will be one that we can use to adjust the darkest pixels so that they print as dmax, without ruining the shadow detail, nor unintentionally darkening or lightening the rest of the image. Illustration 9. This Curve is not a formula, but it is indicative of what I wanted to do. I took the input value of 14 and set it to 0. I moved the white point all the way until all of the gray data was turned white. I am trying to remove everything from the Quick Mask except those pixels which I intend to use as a mask to make my blacks become dmax. My mask should look like the pixels that I want to isolate and turn to dmax. Notice the middle point used to bend the straight line. I needed it to avoid having to pull the white point over too far. This curve tends to produce a softer mask than a straight line; bringing the white point over any further would have produced jagged lines from threshold contrast.

13 Illustration 11. The Quick Mask channel actually needs to be Inverted so that the black areas of the mask which represent what we want to adjust will become selections. However, white represents the selection. Because we want the black areas to become selections and all the white areas to become masked, we will simply Invert.

14 Illustration 12. The Quick Mask is now Inverted. All of the black area will mask our image, while the white areas will be selected when we edit the image to adjust the dmax. When we turn off Quick Mask this channel that we have edited like this will turn into a selection of the Gray channel.

15 Illustration 13. If we click on the Indicate Channel Visibility icon on the Gray channel to make it visible again, the Quick Mask shows us clearly how the masked (red) parts are going to prevent all but the darkest parts of the image from being affected by our edits.

16 Now to choose the correct editing tools to make our 95% pixels become dmax in a manner that is not clumsy. First we will turn off the Quick Mask. Illustration 14. By clicking on the Edit in Standard Mode icon (Q key shortcut!), the Quick Mask is converted into a selection.

17 Illustration 15. The image is zoomed into the point of interest so we can see our shadow detail when we edit. Clicking on Extras turns off the Selection lines so we can see better without those distracting marching ants on our display! The mask is still active, but the Selection lines are now invisible.

18 Illustration 17. Levels is actually a very useful tool for adjusting the Black Point through a mask. First of all, the histogram in the Levels tool shows the masked area only. In this case, I backed off the L value of 14 to decide on 12. I was happy with this level of loss of detail. I could have used a curve to make the adjustment instead. There is more finesse with Curves. Make sure you zoom in to see the detail, and the areas that you are adjusting to become dmax.

19 Illustration 18. The Histogram now shows that the Black Point that we first visualized at L value 14 is now L value 0! So the Black Point is also dmax. In case you curious, pressing the Option (alt) key while clicking on the White Point in the Levels window will allow this same previewing of the white point. But I do not want to turn the pale gray white caps waves into bright white caps. I ll save that for a sunny day and another tutorial.

20 In the histogram of the edited file, you can see small separations. This is unavoidable in 8 bit files. If your image is still in 16 bit mode, you may be able to avoid these. But if you cannot, this small amount of separation will be too difficult for a human eye to see. Humans cannot actually perceive 256 gradation levels at one time. When the gaps (white lines) become thicker, the possibility of posterization occurs and that should be avoided. In our example, we spread L value 14 to 0. If we tried the same technique at L value 20 or higher, we would encounter some posterization. At that point when a gap between what should be 0 is as high as L value 20, its better to choose a more correctly exposed image. Some things can not be repaired without imparting image degradation. Illustration 19. Before and after Histograms show how the shadow area was modified and that everything else remains the same. I hope this technique proves useful to you! Happy printing, Jon Cone