Reproduction of Photogravure Prints

Cu_29_65_Gris_96Introduction. As in other fine art disciplines, one useful aid to the own progress in photogravure is the critical contemplation of the artwork of other artists, successful or not, famous or not. Although the better valuable way to do that is a direct and alive viewing, in those days of Internet connection, we have also the ability to look to a lot of fine art reproductions from other artists. This possibility widely spreads our capability to know styles, paper-ink combinations, finishing techniques and many more aspects about a given artist work. Conversely, other people like artists, curators or potential customers can look at our artwork if it is available on line.

Nevertheless and beside the intrinsic limitations of on screen viewing, there is another drawback compromising our judgement on a given work. The quality of the print reproduction is a crucial aspect that limits the trueness of what we are viewing. Additionally, this original quality level can be modified to a lower range at several different stages:

  • The reproduction system comprising:
    • The lens and camera sensor respective qualities. The lens must be free of distortion or conveniently characterized in order to be fixed by software at raw file level.
    • The type of lighting source. Color temperature and raw file profiling is very important in order to preserve the correct color reproduction. When it is possible, the best option is the flash strobe used in professional photography.
    • The lighting scheme (quality and direction) aiding to enhance or hiding the print textural properties.
    • The processing of the reproduction digital file.
    • The final file format and compression used in order to be able to upload the image to the web.
  • The changes introduced to the properly processed image file by:
    • The system to create the web site where the image is visualized by the Internet users (Dreamweaver, WordPress, Blogger, WebSiteBuilder, etc.). Each of those systems provides different ways to storage and show images in a web site.
    • Internet servers or storage providers. Most Internet providers use some kind of image compressors in order to save server space. This image compression is done after the processing performed by ourselves.
    • The configuration of the web-browser used by the final viewer. Each web-browser (Firefox, Chrome, Safari, Explorer, etc.) uses its own system to show images and not all web site configurations and settings are compatible with all web-browsers.
    • The Video Card of the computer where the image is viewed.
    • The computer display resolution and brightness dynamic range. With computer displays above the mid range level, the most important difference in viewing conditions is the actual size of the image in the screen. As the file in the server has a fixed number of pixels, the image can take a notable difference in size depending on the given display resolution. Because its high resolution rate, Retina Displays from Apple show the images near half size than the majority of standard computer displays. Some web-browsers, in turn, modifies the displaying conditions to fill the screen with the image.
    • The computer display settings. Most users set its display by default, but the size of the contents is very easy to modify with keyboard commands as + or .

In spite of the steps we have not under control, at least in a complete way, the reproduction work, the digital file processing and the generation of the version to upload to the net, are our responsiveness. These are, therefore, the subject of this post.

Reproduction system. From the point of view of the perspective and given essentially flat subjects as photogravure prints are, it is not important the camera-print distance. The better and comfortable reproduction system is a reproduction column allowing for a correct horizontal levelling of both the camera and the print. This ensures a perfect parallelism between the print and the sensor planes and hence, no perspective distortion. If the print is in a vertical plane, attached to a wall or vertical stand, there is very difficult to ensure the perfect parallelism between the print and the sensor planes. Conversely, the proposed reproduction column allows the easy levelling of both (Fig., 1).

Figure 1. Photographic reproduction set up. A Nikon D700 camera body equipped with a Micro-Nikkor 55mm f/3.5 lens, a right angle viewer and a two axis level (click on the image for an enlarged view).

For Internet purposes, almost any medium and high end level digital camera can provide a very fine reproduction in terms of spatial resolution and color fidelity. The better option is to capture a raw file and process it in order to obtain a linear tone reproduction avoiding any color bias. It is important don’t forget that the goal of the reproduction is to show the print tone scale as better as possible. With this kind of cameras, there are no special problems because any photogravure print encompasses a dynamic range wider than the camera capabilities.

Lighting System. The lighting system is also of great importance in the way to ensure the realistic reproduction of the paper texture, the ink thickness and the plate embossing. Although the classical lighting scheme for flat artwork reproduction is a couple of light sources, one on each side of the artwork and at 45º of its surface, this system provides a flat illumination that tends to destroy the above listed print properties. Light coming from both sides counteracts each other and the local texture shadows are almost eliminated. The result is that any texture present in the print is prone to disappear.

The Fig., 2 shows a comparison of the results coming from two lighting schemes. At left, the print is illuminated from both sides with two flash strobes equipped with white diffusers. At right, the same print is reproduced using a solely flash strobe following a diagonal axis from the upper-right to the bottom-left respective corners. The differences in the amount of texture presence are obvious. The reproduction placed at right shows clearly the plate embossing characteristic of gravure prints. This embossing relates immediately to the kind of print we are looking at and provides a sort of volumetric perception in the viewer.

Figure 2. Comparison between the result coming from the two lighting schemes described in the text. At left, two diffused lights, one on each side; the plate embossing and the paper texture are almost disappeared. At right, one diffused light at 45º of the print surface and following an axis from the upper right to the bottom left corner; the plate embossing and the paper texture are now clearly visible, preserving the actual aspect of a photogravure print. The series notation, title and signature are also better visible (click on the image for an enlarged view).

As things are never so easy, the second image is not the simple result of the camera capture. While the proposed system, with an unique light source, is perfect in terms of texture reproduction, it lacks in illumination uniformity (Fig., 3).

Figure 3. Image coming from the raw capture which shows the lack in illumination uniformity caused by the use of only one light fixture. The illumination axis is clearly visible from the upper right to the lower left corner (click on the image for an enlarged view).

Digital Image Processing. As have been previously commented and shown in the Fig., 3, it is necessary a compensation for the lack in illumination uniformity. The good news is that nowadays we have digital image processing to fix this difference in illumination. Photoshop to the rescue! To do that, a Curve Adjustment Layer is added on top of the reproduction image. This layer is adjusted in such a manner to rise the gray value of the bottom-left corner until it reaches an equal value with the original upper-right corner. As the Curve affects now the entire image, it is necessary to add a shade in the Layer Mask that controls the area of the image to be modified. The complete procedure in Adobe Photoshop is shown and explained in the following video. My personal preference is do not completely compensating the difference in illumination. I prefer to keep some amount of illumination gradient that, in my opinion, does not compromise the vision of detail in the print, while retaining the feeling of to be viewing to an object and not to a flat sheet of paper (See the comparison in the Fig., 2).

On line file. The preparation of the file that we will show on line can be accomplished attending to several aspects. One common decision to be taken is the size the image will measure at the display of the on line future viewers. Few years ago, this was an easy calculation. Taking an average resolution for the majority of computer displays of 72ppi, we need so many pixels as the number of inches in size we have decided multiplied by this resolution number. As an example: If our print image must measure eight inches wide when viewed in a computer display, we need a 8inch x 72ppi = 576pix wide file. In this way, we can control  the size the image will be seen.

Nowadays the decision is more complicated. Current available displays exist in a variety of sizes and resolutions, from little, medium and big mobile phones to professional digital image processing displays, with a lot of in between tablets, laptop and desktop computer displays. Additionally, this variety of sizes is combined with several spatial resolutions. Beside that, the exhibition platforms and the web browser offer even more possibilities of displaying the images in sizes that can vary from the original spatial resolution up to several zoom-in or zoom-out, controlled or not by the user.

All that drives to a complete uncertainty about which is the size our print image will take when viewed by an Internet user. In order to constrain this uncertainty, we can prepare the print images for a given Internet media and a given display or displays. My own experience shows that the better option is to show the work in a platform under control, as WordPress blog, Blogger blog, etc. After choose a platform, we can experiment with this platform and a given web-browser in order to analyse how the print image looks with the several options the platform offers. After this analysis, we can decide how many pixels must the image contain to be seen at a given size under well defined conditions. At least, we can show our work in a concrete way when the actual art work is not available. It is important too to realize that all these criteria will change as the technology changes.

Conclusions. In spite of the difficulties that can be derived from the previous discussion, do not forget that, in some cases, a judgement about our work is a direct consequence from the Internet viewing. It is not matter if we are not interested in to acquire new photographic skills, if we do not feel able to acquire it or do not have the necessary equipment. Those recommendations can help someone to commission the work to a skilled professional photographer. Even more, for a given professional assignment and because we know the actual possibilities, we can also judge if the photographer’s work is at the level our artwork deserves.

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