If you've never seen an actual photographic contrast mask, or are unaware of these contrast manipulation techniques, this brief discussion may be of help. Among many prominent professional photographers, contrast masking has become the "buzz" word in recent years. This discussion is focused on the use of photographic contrast masking in traditional black and white darkroom photography work (not digital work). Many of these specialized photographic techniques can also be used for color printing to achieve amazing print quality results. It is important to note that contrast masking is FAR MORE than just the Unsharp Mask!
What is a contrast mask?
A photographic contrast mask is typically a sheet of film (usually made by contacting the original negative on it in various ways) placed against the original negative when printing, or printed separately after the original negative is printed.
There are three basic types of contrast masks:
1) Sandwich type
2) Separate exposure type
Sandwich type masks - These are designed to be placed against the original negative (usually on top of the original negative) so that the images of both original negative and contrast mask are "aligned" or registered. The print is then exposed using this negative/mask sandwich. Since this is a negative-plane mask, you can make any size print at any time without having to remake the contrast mask. Examples of these are Unsharp Masks, Contrast Reduction Masks, Highlight Masks, Dodge Masks and other special masks for increasing contrast. Except folr the Highlight Mask, these can be registered by eye, but a pin-registration system is very helpful to insure accuracy and speed, and is required for Highlight Masks.
Separate Exposure type masks - These are designed to be printed separately from the original negative exposure. The "mask exposure" that is given to the printing paper is usually done after the main (original negative) exposure is given to the paper. Examples of these are Shadow Contrast Increase Masks, Fog Masks (both type 1 and 2) and in some cases Dodge Masks (if used for a totally different effect than when sandwiched). A good pin-registration system MUST be used for all separate exposure type masks.
Paper-Plane type masks - These are placed on or near the surface of the printing paper either during the main print exposure, or after the main print exposure. They are limited to making the exact same-size print every time, unless the mask is re-made to fit a different size print. These masks must initially be aligned by eye prior to the printing session. Once aligned, they can be pin-registered on or near the paper-plane so that re-alignement during the course of the current printing session is not needed.
What mask does what?
Unsharp Masks reduce the overall contrast of the original negative and enhance edge sharpness. The effect is very similar to the digital unsharp mask filter in Adobe Photoshop (or other digital image manipulation software) and indeed the digital counterpart adopted the name from these long-time traditional methods. A higher contrast paper grade is usually necessary (or preferable) when using this mask in order to overcome the general flattening effect and to increase the illusion of sharpness. When over-used, the effect of the unsharp mask can appear too "wired" (to coin a phrase from photographer Dennis McNutt), giving the image an unnatural appearance. When used judiciously, it can open up detail in deep shadows and can result in a crisp print of full detail at the slight expense of midtone contrast. An unsharp mask is actually a form of contrast reduction mask designed to enhance the sharpening effect.
Contrast Reduction Masks raise the general shadow values of the image so that detail in dark shadows is not lost. Upper midtones and highlights normally remain untouched. Edge sharpness is slightly enhanced, usually to a degree that is subtle and seamless. The use of this mask does not normally require a higher contrast paper grade although sometimes it can be helpful. These masks don't have quite as severe of a "flattening" effect on local detail in broad shadow areas as pure Unsharp Masks sometimes do. Because of that, this is a preferable mask to use instead of the Unsharp Mask when a sharpness enhancement is not of primary concern. Modern litho films are perfect materials for contrast reduction masks as the abrupt shouldering effect of litho films is extremely beneficial to the appearance of the final photographic print (this material will prevent excessive detail flattening in the final print).
Highlight Masks add density and contrast to the highlight values of the negative. This results in an increase in the brilliance, and contrast, of highlights in the print. The result is usually seemless and can be quite striking, making it possible to achieve crisp, luminous glowing highlights without affecting the other values of the photograph. It can easily be customized to affect only certain highlights while leaving others untouched.
Dodge Masks are usually placed in sandwich with the original negative when exposing the print. Handmade dodge masks require sketching or painting on a sheet of clear film in the areas that you wish to dodge. A textureless diffusion material (Duratrans or Fujitrans is the ideal substance) is used in the glass carrier as a diffuser to soften the edges of the mask so that it's effect is seamless on the print. Inkjet dodge masks, made by using your computer and an inkjet printer, represent the ultimate in dodge masking, and can even mimic the effect of a highlight mask or contrast reduction mask at times.
Shadow Contrast Increase Masks enhance the depth of fine black detail in the print. This may very well be the "king" of all photographic masks. It can be used to overcome any flattening effects from the use of Unsharp Masks or Contrast Reduction Masks. It can also be used in conjunction with softer paper grades to bring life into otherwise dull shadows. It can be used in conjunction with dodging as well, enhancing the luminosity of dodged shadow or lower midtone areas by helping to "key" the shadow values of the print with fine black accents. These masks require a precise pin-registration system in the enlarger. The Precision Pin-Registration Carrier System was designed to easily handle the accuracy required for this mask. The effect of this mask is beautifully seamless and can end the persistant problem of dull, flat, lifeless shadows. It can help create very tactile and visually stunning photographs.
Fog Masks are extremely useful masks as well. This method of precision flashing will diminish the brightness of distracting highlights or bright spots on the photograph, such as a bright sky filtering through tree branches in a forest scene, or a bright rock in an area of the print that might distract the viewer. It can also darken skies and smooth-out uneven sky values. It is extremely useful as a local fogging tool, and because it is a photographic method (not hand-made), precise fogging (flashing) can be done without affecting adjacent areas. The effect is seamless if not over-done, and it's use can contribute to a smooth and eloquent photograph. It is probably the easiest mask to make and use but it requires a pin-registration carrier system.
Paper-Plane Masks are large sheets of either photographic film or other material which are placed on or slightly above the paper surface. These can be made by hand or by actually exposing large sheets of film. Depending on how they are made, they have different uses. The most common use is localized flashing or fogging of specific areas of the print. There are some limitations to this type of mask, most notably that each is custom made for a specific print size. This masking technique is particularly useful when printing small format negatives.
It sounds a bit daunting!
At first glance it may sound like photographic contrast masking is difficult and time consuming. Quite the opposite is true. Anyone can make effective masks of any type as long as the basics are learned. With even a little experience, these methods can become very intuitive, just like printing! And - a densitometer is not needed in any of these procedures! All of the materials (film, developer, etc.) required for contrast masking are very easy to obtain and are not at all expensive. Please read My First Contrast Mask - Contrast Masking Is Easy! for a story about my first pin-registered contrast mask and how it increased my enthusiasm for photography.
That's it for the basics. Photographic Contrast Masking can truly bring a new level of excitement to darkroom work. The problems of achieving the highest level of print quality which have plagued photographers for decades can now be overcome by some or all of these simple and seamless techniques. For more basic information on photographic contrast masking please see the Masking FAQ's page.
photographs on this site are copyright © Lynn Radeka. All rights reserved.
Precision Pin-Registration Carrier System copyright © 2002 Lynn Radeka. Patent pending.
Contrast Masking Kit copyright © 2000 Lynn Radeka.