Originally Posted by Les McLean
Typically an unsharp mask will add between .14-.35 of compensating (reducing) density to the camera negative. This reduction offset is then compensated by increasing the contrast grade at which the unsharp mask and camera negative are printed. The benefit to the unsharp masking procedure is that there is an increase in apparent print sharpness (due to edge effects) and an increase in local contrast. An unsharp mask is preferable in my experience to the other means of compensating for excessive negative density range (flashing of the paper). The reason is that paper flashing will compress print highlights whereas unsharp masking will compress shadow separation.
If I were going to develop a negative in which I wanted to unsharp mask and split grade print, I would target my negative density range for 1.55-1.65. The unsharp mask would effectively lower the net density range into the 1.25-1.45 range that would allow for split grade printing to be utilized. This targeted negative density range would be very nearly what one would want for contact printing on Azo. If I were using Pyrocat, I would then use the documentation that Sandy King has kindly provided insofar as differing films and developer dilution on the Unblinkingeye.com site.
I personally do not split grade print a great deal today other then to utilize differing contrast grades for burning.
Les: Donald Miller's description of the effects of unsharp masking is very thorough - one of the effects of the unsharp mask is to reduce the overall density (density range) of what one will print (the sandwich). In my case, this reduction is in the order of 0.3 - 0.4 as a very minimum. The sandwiches (negatives+mask) thus have density ranges that are lower than the density range of the original negatives by the above factors.
I printed two sandwiches using the split-filter / split-grade technique. These sandwiches had density ranges of 0.61 and 0.89 and therefore they required magenta filtration of Grade 3+ and Grade 4+.
For the two tests I conducted:
DRN = density range of original negative
DRS = density range of resulting sandwich
DRM = density range of the mask
DRN1 = 1.30
DRS1 = 0.61 the mask was very strong DRM1 = 0.69
DRN2 = 1.33
DRS2 = 0.89 the mask had a density range of DRM2 = 0.44
In one case I used maximum yellow filtration (170Y), which approximates Filter 00 <with my enlarger> and in the other case I used 70Y, the equivalent (with my enlarger) of Grade 0. In both cases I used a magenta setting of 170 units - which gives me a Filter 4+ but not quite a Filter 5. In both cases I started with the yellow filtration first to determine the xposure for the highlights and in both cases I reduced this exposure by 10% to account for the added density (in the light areas) contributed by the magenta filtration.
In both tests I ended up with prints that were very close to the ones I had obtained using a single magenta setting (single filter ?) but the prints were "muddy" when compared with the ones obtained using a single filter setting. The local contrast, especially in the middle tones and shadows (Zones III through VI) was not as 'strong' as with the prints obtained using single filtration. I visually inspected the prints very carefully and measured the high values with a reflection densitometer to make surte the high values 'matched' - they did.
I believe the results above results correlate with your statement that split-grade /split-filter works well when the density range of the negative is ample (contrasty negative) but that you have obtained better results using single filtration when the density range of the negative is low.
If my interpretation of your conclusions is correct, I should stay with my single-filter technique, as all my sandwiches have density ranges below 0.9. Would this conclusion be correct, according to your experience?
BTW, I am most appreciative of the time you are spending reading my notes and providing me with your insigh and experience.
It has been my experience that an unsharp mask with the density that you indicate will be greater then what one can compensate for with adjustments to effect higher contrast grades at the printing stage. The net density is just too low to offset. Thus one is left with three choices, as I see them. The first is to develop a camera negative above the density range of 1.30 (more like 1.55-1.65). The second is to produce unsharp masks of less density (typically .35 maximum). The third would be to produce a third mask which is typically called a shadow value enhancement mask.
The shadow value enhancement mask is produced by producing a sharp positive mask of high density. This would typically expose everything but the deep shadow values. From this sharp positive a contact sharp negative mask is produced that will allow printing in of the shadow values with a second exposure. This does obviously require pin registration at the enlarger stage.
This does fall outside the realm of split grade printing.
Thank you for your insight. I am afraid I do not quite understand your posting.
i) My sandwiches, with density ranges of 0.8 - 0.9, print well when I use magenta filtration settings of 80M - 100M. I like very much the local contrast I am able to obtain with these sandwiches. I develop my original negative so as to obtain a density range of 1.2. I make my unsharpo masks so as to achieve a mask density range of 0.3 - 0.4. I then end up my sandwiches with density ranges of 0.8 - 0.9. Ocassionally, I will create a stronger mask in order to arrive at a sandwich with density range of 0.65 - 0.70.
ii) I do have a pin registration device to produce my unsharp masks but do not have a pin registration unit in my negative carrier. Consequently, I do not have the luxury to create several masks; take the negative out of the <glass> carrier, remove mask #1 and insert mask #2. Do you know anybody who could sell me a pin registration device for my enlarger head: a 10"x10" Omega F Super Chromega II?
iii) My printing technique is to measure the density range of the sandwich as use a filtration setting that accomodates that density range. I have conducted tests to arrive at what those filtration settings are for different density ranges. So, I measure the density range using a densitomere and then adjust my dichroic filter settings based upon my charts. I had never used the split-filter technique.
iv) Out of curiosity and a natural desire to learn more and become better at this craft, I decided to try the split-filter technique. I ended up my almost-identical prints but the ones produced with the split-filter technique look somewhat "muddy". My big question is: "are my negative density ranges too low to take advantage of this technique?"
To: Donald, re: correction
Correction: My big question is: Are the density ranges of my sandwiches (0.8 to 0.9) to low to take advantage of the split-filter / split-grade technique?
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Originally Posted by JackRosa
My answer to your question based in my experience is "yes" that your net density is too low to effect the full use of split grade printing. My experience would indicate that a net density of 1.25-1.35 would be more ideal to utilize split grade printing.
Now I will go on to say that I believe that one can achieve the same effect utilizing a single grade setting as one could by using split grade printing with this one very important departure...that is when it comes to dodging and burning. In other words one would want to print a given negative (DR 1.20) at a net grade 2.5 in printing a negative. In your instance this is more like 4.5 with your net density of .80 to .90. It may be nice in some instances to increase the contrast for printing in some shadows, for instance, to achieve greater low tonal value separation.
Using split grade printing one could dodge an important high tonal value on the low contrast exposure. Just as one could burn in a low value with the high contrast exposure.
If we were printing a negative (DR 1.20) at a grade 2.5 (whether split or single contrast setting) then we could increase the contrast to grade 4 from 2.5 in burning in a shadow region to achieve greater separation. With the net density that you indicate, you have nothing left to increase contrast in burning in a low value since you are already pretty well maxed out at grade 4.5.
Split grade printing will still allow you to achieve the local contrast that you value in your prints and add more creative latitude through the burning and dodging steps. However I think that your net density as you have indicated is too low to fully utilize it.
I hope that this answers your questions.
You might try Ingallis (sp?). I think that he advertises in View Camera and is located in Canada. He makes registration equipment for a variety of enlarging equipment and probably has the capability to provide you what you want.
Originally Posted by JackRosa
to your point , I use split filtering this way.
First I determine a filtration and density that I feel looks right for the image I am working on.
I then drop 1/2 grade from this and slightly reduce the time in exposure.
This initial exposure I will dodge and burn as necessary at this filtration
Next I will put in the grade 5 filter in for a short blast . This exposure seems to affect the blacks . I will also burn in areas for more contrast at this stage.(usually I will have dodged in the initial exposure , so that I can burn back in with the 5 filter)
Once I like this final contrast , I may or may not burn in Highlight areas with the 00 filter.
I find with Pyro negatives I can control the whole image quite easily.
I first started with just the 00 and 5 filters , and I must say it worked but not to my liking . Using three filters may sound crazy but I like the results.
As well pre flashing the paper will help in extreme cases where I need detail in areas that the above will not handle
Thank You to Donald Miller
Thank You for your insight. I completely understand your point now.
And <also> thank you for the tip re: pin-registration ~ Inglis. As a matter of fact, I bought my registration unit from him. It never ocurred to me that he might be able to supply a mechanism for pin registration that mounts to my enlarger head. I will contact him.
I just recently returned to darkroom printing and experience some problem with my negs which was OK for scanning on Epson 4990 - they seem to be too low in contrast and printing them even with highest contrast filter (Ilford below lens set) or highest magenta setting at DeVere 504 Dichromat head gives me too low contrast. If I got it right split grade printing isn't recommended for low contrast negs? Any other possible way to increase contrast?