Creating Enlarged Separation Negatives - How best to do it?

[holmburgers]

Greg, what a great find! Allow me to read up...

 

[michaelbsc]

I mean that 11x14" pan film would be an obstacle. Yes, 4x5" is fine and I have a lot of it.

Where are you finding the x-ray dupe film? I'm searching for CSX but haven't come up with anything yet....

I recall a discussion about the white light and I think it is not panchromatic unfortunately.

Greybeard, this is great... you're helping me put this puzzle together!

I think I remember a discussion about the white light film as well, perhaps the same discussion.

What I recall is that the duplicating system systems are either "UV" or "White Light" systems, with the UV systems being more expensive and somehow "super-duper" for medical duplication. But they need a UV source to expose the film. I don't know if they're faster, or better controlled, or higher resolution, or all of those, or just more expensive with rest of the qualities being inside the users head.

The "white light" film is film that is sensitive to visible light, but as holmburgers says it isn't necessarily panchromatic. Nor is its spectral sensitivity linear in a way that would make it useful for making separations. Basically, the white light label implies "Not UV" to the radiology crowd.

MB

 

[Hexavalent]

Wow. It's been a while since I've read anything that detailed on color separation. I sort of knew what was involved, but it's a shock to see it confirmed....

Thanks, Greg!

That's simple compared to CYMK seps with UCA, UCR, dot gain and trapping needed for offset litho... and then there is the screening issue

 

[Jim Noel]

Lith film will work very well and is easily obtained from Freestyle. If developed in properly diluted film developer, not paper developer, a negative of very long scale is easily produced.

 

[holmburgers]

Hey Greg,

The technical stuff on pg. 3 about curve shapes and stuff is awesome information. But I need a densitometer.....

Tell me this, can one use a scanner as a reliable method for densitometry? Like, let's say we have a standardized step wedge that we can use as a calibration standard, can we then get useful values of our own negatives? This might be worth exploring... and before anyone says a damn thing about scanners.... well, nevermind.



Jim, I literally can't find litho film for sale anymore. If you can find it, please let me know. I've been looking actually, but it's like it has dropped off the Earth, or I'm terrible at searching. It's definitely an appealing option.

 

[holmburgers]

Dead Link Removed

This mammography film is available cheaply in various places. I'm tempted... Do any of the curves/graphs shout disaster? Tweaking is to be expected of course.

 

[holmburgers]

This old dog? 270726863037

 

[holmburgers]

It'd also be nice to pinpoint problems in the dye-transfer stage, and for testing dyes especially.

I need something small though. Any recommendations? The Tobias looks fairly compact.

 

[holmburgers]

Dead Link Removed

So I'm seconds away from buying some of this film. Look at the gamma curve though, is that unusual or am I just unfamiliar with gamma curves?

I'm also not sure what this line means, "A particular strong point is the system’s high dynamic
range. For every image, the contrast is optimized for each
density range. Equally, the system provides excellent
visualization of details which are further enhanced by the
masking effect of high maximum density in the non-image
area adjacent to the skin-line."

Any opinion would be most appreciated.

 

[holmburgers]

Hmm, that link doesn't work all the time. Here's what the gamma curve looks like...

It just seems, well, odd to me. But I only know enough to be dangerous when it comes to sensitometry.

 

[holmburgers]

Any verdict?

 

[holmburgers]

Well, all I'm trying to determine is if I'm gonna get a normal looking image. The way the graph dips back down makes me think it's some kind of strange film like Agfacontour.

I basically just don't understand how to read gamma curves.

If I can straighten out the contrast curve, the dichromated gelatin doesn't need to know what kind of film it is.

 

[holmburgers]

Damn, you're just like those teachers that don't give you answers but make you learn it for yourself. WHAT RUBBISH!

 

[greybeard]

I am a teacher that makes you learn it for yourself.

Good for you!

My students want me to spoon feed them...

Personally, I think the proper use for a spoon when it comes to education is that it should be one of the huge wooden ones, with the understanding that "insight which cannot be introduced gently into the head of a student must sometimes be instilled forcefully at the other end"


On the topic of densitometers: it might be worth looking for one of the models with both visible light and UV channels. These were made specifically for the graphics arts trade, where some of the materials (lith film, for example) are essentially only blue-sensitive. There is a body of opinion that film processed in a staining developer can only be evaluated properly by using a UV densitometer; perhaps someone knowledgeable will comment on this.

 

[holmburgers]

Ok, so from what little I've read thus far in the sensitometry handbook, is this xray film going to have incredibly high contrast in the middle range and decreasing contrast on the outer limits? (great show by the way.. Outer Limits)

It's hard to extrapolate, since the kodak handbuch (that's german for handbook) doesn't actually show a gamma curve, and does this xray film even have a straight line portion? yuk yuk yuk...

Greybeard, what do you think about this xray film that I've posted? None will look good on paper I suspect.

Either way, I'm gonna read this thing and get it sorted out. Densitometry is one thing I need to beef up on.

 

[holmburgers]

Hey gang,

Last night I got into the sensitometry workbook. Finally, I grasp logs! I wish they just called it "the exponent over 10 that equals ____" though. I think the word log immediately induces some kind of dormant learning disability in me. But anyways...

Quick question; the book clearly states that visual & photometric densitometers should give identical results if used properly, though I'm wondering about what effect color would have in judging the density within a visual unit. For instance, the blue base of an X-ray film. It seems like it might affect your perception. But, I've never even looked into one so I don't really know.. soliciting opinions.

 

[greybeard]

holmburgers,

I'm pleased to hear the you went into the book; I haven't had a chance to look at it, but maybe this will make sense:

The "sensitometric [or H&D] curve" on the Agfa literature shows pretty extreme contrast; the straight line portion goes from d=0.5 to d=3.5+ in only two stops of exposure (log E=1.2 ---> log E=1.8, and one stop is 0.3 log exposure units). However, this is for x-ray use and you would presumably be using a much less active developer, and see far lower contrast.

The "gamma curve" is the slope of the density curve, plotted against the film density; notice that it goes to zero near d=0 and again near d=4.5, which is where the H&D curve goes flat, and peaks where the straight-line portion of the sensitometric curve is found. All of the funny business is up above d=3.5, which is a pretty dense negative.

I seem to recall that the Kodak publication mentioned a maximum density of something like 2.5 for color separations, so your problem would be to get the density range of your original (probably something like d=0.1 to d=1.5 or so) to translate to d=0.1 ---> d=2.5 in the separations. The problem with the x-ray film would appear to be that really long "toe"; you might have to pre-expose in order to get up onto the linear portion, and then you would have a lot of base density to print through. But the developer will have a lot to do with this. The x-ray film curve is actually very gentle compared to a lithographic film (in lith developer) which goes from nothing to dead black with a negligible exposure change, and folks successfully tame that stuff for analog photography.

So I would suggest getting the smallest sample possible, and doing some experiments; after all "one clean experiment is worth a thousand dirty calculations" and the Kodak pub should give some idea of the targets that you are shooting for.

If you'll keep studying, we'll put away that big wooden spoon......

 

[holmburgers]

Thanks greybeard.

Based off what you just told me, I went ahead and bought 2 100-sheet boxes of 18x24 (I assume centimeters... I'll take inches though.. ) for $37. NOT BAD!

eBay item #150581436367. 2 boxes left... get 'em while they're hot! It's expired 2009 by the way.

That much film should give me a lot of material for experimenting. I can certainly live with pre-flash, if it comes to that, but I also think that your statement, "The x-ray film curve is actually very gentle compared to a lithographic film (in lith developer) which goes from nothing to dead black with a negligible exposure change, and folks successfully tame that stuff for analog photography.", is very telling.

If this film can do what needs to be done, then it will be an incredibly liberating discovery. Incredibly large prints will be possible with a minimal expense. I would've paid nearly that price for 40 sheets of inkjet transparency paper had I chosen the digital route. The key now is figuring this beast out, and I think a densitometer will be my next planned purchase.

 

[holmburgers]

Hey all, just a little update. So the x-ray sheets arrived yesterday and I couldn't be happier. 200 sheets, wow, that's a lot of experimenting.

The size is also nice, just a little bit less than 8x10". So I won't be wasting materials but I'll have respectable sizes to get it all worked out.

So here's what I've basically come to:

If coming from a E6 transparency, I will copy 1:1 (either contact or w/ copy setup) onto panchromatic b&w film and reversal process it. Then this can be enlarged to the X-ray film to create a negative.

If coming from a C41 color neg, I will do the same, except no reversal process will be necessary.

To me, this represents simplicity at its finest. I'm sure there will be difficulties taming the tonalities, particularly in the reversal processed positives, but as long as the separation negatives are equal in contrast, the color should be passable (assuming a matched dye-set and all that jazz...). Plus, this will force me to become better at controlling my processes; a valuable skill to have.

So my first experiments will be to enlarge to the x-ray film and develop in either HC-110 or Dektol (soon to be Liquidol); I can't say which would be inherently more suitable, can you? Before exposure, I'll place a gray card at the baseboard and take a series of readings from my spot meter to establish a baseline illumination. It'd be great to have an enlarging meter, but I've gotta work with what I've got and stop buying "accoutrements". I'm discovering that you can keep buying stuff as long as you wish to and there will always be a justification... and at the moment I'm just sick of buying stuff.

As a thought experiment; let's say we are stuck with one film (or paper) and one developer. What controls are available without changing these 2 constants? For instance, temperature (not something I'm fond of toying with), additional chemicals (K-bromide?), pre-flashing (as noted by GB) and what else?

 

[holmburgers]

Well allow me to enlighten you...

There's no way I can afford to make 11x14" or larger prints using panchromatic film for the separations. Period.

My process requires contact-size separation negatives. This is the key difference between what I'm doing and what Kodak's dye-transfer process did.

As you know, Kodak's matrix film was a silver-halide film that was then developed in a high-powered tanning developer. This was then washed in hot water to reveal the gelatin relief. This relief is responsible for absorbing gelatin in proportion to its thickness and thus transferring it proportionally to the paper. The enlargments were done in a typical enlarger, from small negatives.

Since I'm not in the business of making emulsions, it occurred to me that a carbon print is basically the same thing, a gelatin relief. Ergo, I am making pigmentless gelatin tissues and these become my gelatin relief matrices. These cannot be exposed in an enlarger, they have to be contact printed with UV light.

Having small b&w separation positives will allow me to enlarge to an orthochromatic film (cheaper!) like X-ray. Furthermore, I can use the same seps to enlarge to many different sizes if I decide to make a larger or smaller print in the future.

 

[holmburgers]

I think you're right. Contact copying 4x5" seems doable, but 35mm seems like a nightmare. That's why I'm thinking to use a copy setup for 35mm, with a fine grained film (Pan F Plus or something)

One other snag is going to be getting identically sized enlarged negatives. Since I'll have to remove each sep. poz. from the negative carrier and replace it with the next, there's room for error.

As per the sensitometry, are you saying that reversal processing is going to get wonky? I had this thought too.

OH well, this is all part of the fun & discovery of it. I'm not expecting immaculate results right out of the gate, but I'm always amazed at how good even loose approximations of theory can look.

 

[holmburgers]

So you think that enlarging 35mm to 4x5" would be better than copying 1:1 onto 35mm? I can dig that..

Yeah, pin registration would be awesome. Unfortunately they are suuuuper expensive.

I'm hoping to get by with visually aligning the enlarged negatives and then punching them with a 2-hole punch. Visual registration is a tried and true technique, but no doubt a PITA.

Someday...

 

[holmburgers]

Beseler 45MCR.

I've seriously thought about making my own punch/registration stuff.. Any ideas how?

 

[holmburgers]

I've currently got a 2-hole punch that I've been using for my screen-plate experiments. The only problem is that it seriously impedes into the image area.

The Inglis & Condit ($$) punches use smaller pins closer to the edge. Here's a good set of pictures... (there was a url link here which no longer exists)

 

[holmburgers]

Actually, the more I think about, registration in my enlarger won't be of any benefit whatsover. It's the film that I'm projecting to, and the magnification factor that are really important. Now, if I was masking, this would make sense, but at this stage it's unnecessary.

What I do need to do is register my negatives, and then register my matrices. Some DT printers actually align & punch the matrices by placing them in their respective dye baths and lining them up visually on a light table. This seems tedious.

But, if I can accurately punch the large negatives in perfect registration (visually), all I will need to do is have a registration-board. Then, the matrices can be punched before exposure and as long as everything gets placed on the same board, I should be hunky dory. Then, I can use the same board for laying down the mats.

Voila!

That means I'll just have to make the matrices a bit longer than necessary, to accomdate the 2-hole punch.