Safelight for RA-4 printing?

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Donald Qualls

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Aaah. That's way better than 3dB (2x) difference. Even if it's log, I've seen published information that used natural log instead of log10, and didn't say so -- and e3 isn't much more than 3 stops. Ten stops ought to make it quite reasonable to have narrow-band LED lighting bright enough find dropped items, make sure paper is right way up, and ensure chemical coverage in the trays, with a reasonable safe time.
 

Bikerider

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It is set between 9 and 10 which makes it easy to see what I am doing after a short while after the main light goes out. For B&W I always set it on 'full' and even without a red filter I have never had problems with fogging. I always work with the paper in my shadow from the light because the lamp is on the wall behind me but points to the ceiling so the light is even more diffused. The average exposure for a 12x16 colour print is between 20-30 seconds. (It is a bit longer for B&W as it is less sensitive and depending on the filtration)
 
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Bob Carnie

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Every C print I ever made was in total darkness.
The new paper is much faster than the papers I used with enlargers, I believe due to the digital printers requirements...

This paper is so fast any light may have an effect on it.
 

twelvetone12

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I have an old Kodak colour safelight, extremely dim, and I must be at a couple meters from the paper or it will fog the paper, and even then the paper will get fogged given enough time (a couple minutes, actually). I use it for tests, but for real printing I do it in total darkness.
 

DREW WILEY

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Bob, digital optimization was just a bit of boost in green sensitivity due to the green laser being weaker than red or blue, but not a significant speed change overall. Then there was an attempt to get blacks blacker - curve tweaking - which seems to have been the biggest complaint with early digital printers. But enlarger times are about the same, as is starter color pack. But RA4 papers are about six stops faster than what I was doing in Ciba. So when I stated that I use a little Jobo Minilux light for loading the reel holder, I meant just a few seconds at a time.
 

Michael Firstlight

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I thought Kodak papers had a notch cut in its (non)sensitivity for 89nm light - but it had to be +/- 1nm in accuracy. I never used one, but wonder if Fuji Crystal Archive had the same.
 

DREW WILEY

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Fuji specifically states total darkness, no safelight. Maybe that's just being cautious or diverting liability, but when they state something, they seem to mean it.
 

mshchem

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I thought Kodak papers had a notch cut in its (non)sensitivity for 89nm light - but it had to be +/- 1nm in accuracy. I never used one, but wonder if Fuji Crystal Archive had the same.
I mean no offense, but that seems like science fiction. You would need some serious equipment like a spectrometer. An emission source that is like a low pressure sodium light emitting very narrow lines.
These lamps produce a virtually monochromatic light averaging a 589.3 nm wavelength (actually two dominant spectral lines very close together at 589.0 and 589.6 nm).
The reason that, given time, sodium vapor lights work is your eyes are quite sensitive to this light.

There's no safelight that produces enough light, that won't fog color paper, that will do you any good without giving your eyes time to adjust.

Rods and cones, Vitamin A. .........
 

Bob Carnie

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That is not what I observed when I changed from optical RA4 paper to Digital RA4 paper. I made the change about 2004 when I purchased the lambda, I also noticed that the colour of the paper was different if you just brought it out to daylight without processing..
 

DREW WILEY

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There are different lines of Fuji CA paper, Bob. There is a full line of cross platform papers designed for both enlarger and laser use, and a specifically "digital" line balanced somewhat differently, which I've heard of people in the EU successfully balancing for optical colorheads too, but which I've never personally tried. It's actually uncommon here; I don't know about Canada. The deluxe Fujiflex polyester product is of the former category, and very similar in balance to Super C, CAii etc, with identical blue overcoat. But there have been incremental changes in the CA lineup all along. Even a significant change was made in Fujiflex a few years ago; but it can only be detected on the box via batch number and a rather hard to find notice buried somewhere in Fuji's tech announcements. The struggle with green diodes is inherent because green light is actually produced by filtering residual green out of a red diode. Apparently no true green diodes even exist yet, but I haven't kept up on the latest possibilities. So they have to boost more power and use dense filtration to subtract the dominant red just to get pure green out of it. So in the meantime it made sense to increase the green sensitivity of dedicated papers too. All of this is factored into their paper specification for the dominant brands of laser printers, including whatever Chromiras might still be in use.
 
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Bikerider

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Fuji specifically states total darkness, no safelight. Maybe that's just being cautious or diverting liability, but when they state something, they seem to mean it.

I think they will just be protecting their corporate backsides. As the Duka is not available new, if anyone who is just taking up RA4 printing tries a 'safelight; and use an ordinary one and get the paper fogged they could have a complaint. So stating what to us is the 'obvious' that it has to be used in total darkness then they can state that they warned people.

For what it is worth when I converted from Fuji paper to Kodak it was noticeable that the Kodak paper was slightly less sensitive. A Fuji print that would have to be exposed for 20 seconds with Kodak 25 would probably be more accurate. Oddly enough filtration was pretty much the same with both papers.
 

DREW WILEY

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Of course. Fuji has no control over how well somebody might test or maintain their safelight filters. And someone like me can't afford to screw up a thousand dollar roll of paper. So total darkness makes sense as the safest advice.
 

pentaxuser

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Thanks. So about a fifth of the way along in terms of numbers. On my 0-35 this translates to about 7 Useful stuff to know and from someone who does RA4 regularly so has experience of what is safe

pentaxuser
 

Bikerider

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Of course. Fuji has no control over how well somebody might test or maintain their safelight filters. And someone like me can't afford to screw up a thousand dollar roll of paper. So total darkness makes sense as the safest advice.

I use rolls of paper kept in a home made paper dispenser .This is the Mk2 version made from riveted alloy, where the 1st one was wooden.

I buy 12" x 88m rolls of Kodak Endura which costs me about £105 - £110 depending on the supplier. I am limited to 12" wide simply because the weight of a 16" wide roll is just to heavy to manhandle. These 12" rolls, in theory should give me 214 sheets of 12x16. In practice I would think 200 sheets would be nearer the mark after wastage. If you compare this to the price of 4 x 50 sheet boxes of Fuji, you will see it is quite a saving. This coupled with the ability to cut any size I want within these parameters is why I use a roll rather than boxed sheets.
 

DREW WILEY

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You're not comparing apples to apples. I was referring to 40 inch wide rolls of polyester-based Fujiflex, not RC paper. It's an inherently more expensive medium and only comes in bigger rolls. It has a richer look, much like Cibachrome. Kodak has nothing comparable.
 

koraks

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The struggle with green diodes is inherent because green light is actually produced by filtering residual green out of a red diode.
This is an overly simplified and technically incorrect assessment - not just for today's situation, but in general.

There are essentially two ways to make green leds and both are currently used by manufacturers. Each has their own drawbacks and advantages.
The first is using a blue led with a phosphor on top that converts the blue light into green (wavelength shifting). In practice this results in a fairly wide bandwidth and the challenge is to get good conversion efficiency, but the advantage is that the high-efficiency of blue leds can be exploited.
The second approach is to make a pure green emitter, no wavelength converting phosphors involved. These are technically challenging to make with high output/efficiency mostly due to problems with substrate and coating purity and homogeneity. Pure green led technology for low outputs dates back to the 1930s (conceptually) and 1960s-70s (commercially). They've been on the store shelves for decades and became available to the general public at very low costs in the early 1980s. Today's requirements are of course high output and efficiency, and lots of research is being done to overcome the efficiency gap in the green and yellow parts of the spectrum. The challenge is fundamentally the same for green semiconductor lasers, but the bar is a higher due to the higher requirements on material homogeneity and purity.

Hence, we currently have the option of fairly efficient, but wide bandwidth green leds (the phosphor coated type), or lower efficiency but very spectrally pure true green emitters. If, as a consumer, you buy a green led, you're of course usually not entirely sure which type you've got unless you either do bandwidth and efficiency measurements, or if a sufficiently detailed datasheet happens to be available.
 

iakustov

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what are affordable options for IR / night vision goggles to use in the darkroom? The ones I see on eBay are currently at 600USD.
I don't care about being in total darkness when doing enlargements and RA4, but for RA4 contact prints / proofs this is a nightmare so I am searching for a solution.
 

Tom Kershaw

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Drew,

So you are exposing negatives in the enlarger to make optical prints directly on Fujiflex?

Tom
 

Bikerider

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Not being psychic, nor possessing a crystal ball, Neither I or others reading this were aware you were using FUJIFLEX and not RA4 PAPER. You made no reference to this so yes the goal posts have changed but as you did not make it clear your response is a bit of a non reply.
 

MattKing

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I believe Fujiflex is RA4 paper.
 
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Donald Qualls

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Try looking at monocle units. Amazon has those starting just over $100, though I don't know (don't think) those include IR illuminators. Adding a string of IR LEDs powered by a small battery is trivial, though.

Head mounting and sealing the output light against leaks that might fog your materials is left as an exercise...
 

MattKing

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