Paper speeds??

[Ducky]

I know film has diferent speeds making them more or less light sensitive. Does photographic paper have similar qualities.
I know paper 'grade' has to do with contrast and softness. Is there a speed rating for paper?

My dilemma: I have a vintage contact print box, adjustable from 2x2 to 4x5. It has a safe light bulb that is on all the time and it has a white light that goes on when I press the lid down, count to 5 and open the lid. All of this I learned from my father using a similar box and a 15 watt bulb.However, I cannot get anything except overexposed prints. Five seconds and I get a black print. Lower the wattage and it does not matter. The paper has not been opened in the light or similar errors. Chemicals are fresh.
Is there a slow paper? I'm about to rig a flashlight bulb in the box.
A little help please

 

[JamesH]

From experiments with pinholes I found Ilford Multigrade to have a speed of about 12 iso.
Other papers will vary though I doubt by much.


Edit:
Can't you expose a test strip first?

 

[Chriscrawfordphoto]

Yes, some papers are faster than others. Ilford, Kodak, and AGFA used to publish speeds for thier papers that were determined by an ISO method, but it was a different system than used for film, so you couldn't use a light meter for them...it was more for comparison purposes for customers who needed faster exposure times for some reason. Some papers like Kodak Ektalure and Oriental Warmtone were SLOW. Ilfochrome paper was the worst for speed, super slow.

 

[JamesH]

Hi Chris.
Yes you're right about the different "standards" used to determine sensitivity.

In documentation Ilford states their multigrade as 400 (IIRC) though in daylight, used as a "film" it is more like 8 or 12.

 

[degruyl]

"The wonderful thing about standards is that there are so many to choose from"

In any case, first: distance of bulb to paper matters. Quite a bit. Most setups for contact prints have the bulb feet away from the paper, not inches. Second: there are light meters for use in printing. I use the darkroom automation system. Third: have a look at the darkroom automation website http://www.darkroomautomation.com/support/index.htm There is some speed test data on there that might be of use to you.

Good luck, and maybe cut down the wattage by using a filter?

 

[Nicholas O. Lindan]

... I have a vintage contact print box .... I cannot get anything except overexposed prints ... Is there a slow paper?

These printing boxes were made for 'contact paper' - Kodak's Velox and Azo were two popular ones - rather than enlarging paper. These papers had chloride emulsions that were very slow.

One of the few contacting papers still available is Foma Fomalux, it is available from Freestyle.

The other alternative is to put a neutral density filter on the backside of the printing box's glass. B&H sells Rosco neutral density gells. ND .9 will cut the light by 3 stops.

ISO speeds for enlarging paper are different from the ASA/DIN/ISO/EI speeds for film. I don't think there are any speed standards for contact paper.

 

[Roger Hicks]

Nicholas has answered the question fully.

Incidentally, treating paper as 'film' in a camera (paper negs) I've generally found an ISO film equivalent (NOT the same as an ISO paper speed) to be more like 3-6 than the 8-12 found by others.

Cheers,

R.

 

[MartinP]

Can you adapt the box to use either indirect daylight or, more controllably, a lamp external to the box - say on the other side of the room ? Probably that would be effectively similar to having a piece of glass on top of the negative/paper sandwich and using an enlarger or table-lamp as the light source, in which it would be simpler to not use the contact-box.

EDIT: I have just realised that you may also have more success with no 'safelight' bulb on at all, as that is likely to be no longer safe due to age or possibly the spectrum it puts out.

 

[Dwig]

...
Incidentally, treating paper as 'film' in a camera (paper negs) I've generally found an ISO film equivalent (NOT the same as an ISO paper speed) to be more like 3-6 than the 8-12 found by others. ...

Several points:

1. These speeds (Film ISO equiv of 3-12) are typical of "enlarging" class papers. "Contact" class papers are many stops slower (more in the Film ISO equiv of 0.5-0.1 range).

2. These speed equivalents should be stated for an exposure time range. Papers suffer from reciprocity failure just like film. Papers are generally engineered to be reasonably linear over a 5-30 second exposure range. It is this exposure range for which the official speeds are stated. Outside of this range, speeds will vary. At pin-hole camera exposure times they will vary significantly, one source for the wide speed differences seen by some experimenters.

3. Variable-contrast papers will vary in speed depending on which filter is used. Many modern filter sets incorporate some neutral density values to balance the speeds so that using a filter set matched to your paper will result in consistent speeds with one speed for a range of lower contrasts and one for the higher. Using CC filters (e.g. color head filtration) doesn't produce this balanced speed set. This balanced filter set idea was introduced in the '60s by Dupont for their Varilour papers. It wasn't adopted by Kodak or Ilford for over a decade.

 

[ErnestoJL]

Some friends who make pinhole photography using paper instead of film told me that they are used to calculate exposure for daylight based on an equivalent ISO 6 sensitivity.
BTW, the Gosen Lunasix (Luna Pro in the US) had an accesory named Labor which was to be placed in front of the CdS cell. This exp. meter has marked sensitivities as low as 0.8 ASA/ISO which were to be used when the meter was needed for enlarging, thus covering the usual papers rating, including paper for contact copies.
For my personal experience, I agree with Roger about values from 3 to 6 ISO.

 

[Ducky]

Many more comments and much more information than I exoected.
Nicholas: I did not know about contact paper, maybe my father mentioned it and I forgot. I'll check it out.
MartinP: Taking out the safe light is a good idea, that occurred to me last night as well.

Thanks all, very much.

 

[Tom A]

Unless your bulb (white light) is using a transformer - just wire in a rheostat (dimmer switch) to it. Do some tests and establish the time needed for modern, faster paper. The old AZO or bromide papers were really slow.

 

[Ducky]

Thanks, Tom, I never thought of that. I need to replace the fabric covered wiring anyway, hate to do it since it's vintage but I guess I can keep it and solder it all back in at some point.

 

[zauhar]

I'm resurrecting this thread to ask from a different angle - How does the finish of the paper affect its speed?

It is my impression that glossy paper is much faster than matte finish. Any truth to that or am I fooling myself?

Randy

 

[al1966]

Unless your bulb (white light) is using a transformer - just wire in a rheostat (dimmer switch) to it. Do some tests and establish the time needed for modern, faster paper. The old AZO or bromide papers were really slow.

If it uses a transformer you could always put a variable voltage regulator after the transformer.