Peter, I think most of what you ask can be found in the paper neg threads, but there is one issue that I don't think has been discussed recently, namely whether the RC papers that have a developer incorporated are appropriate for pinhole. I think you wouldn't have much control over contrast during development if dev is incorporated, using dilute dev or snatching probably won't help much. Maybe if you can get a soft grade or multigrade RC paper like the Forte RC without developer incorporated, that'd be a good choice. But honestly I don't know anything about most of the RC papers and dev incorporation, so I hope someone else can chime in with some info.
Thanks. I will have a look in the paper neg. thread then. I think I will use portriga speed RC paper. I don't believe they have developer in the coating. But I may be wrong. Just one more thing before I head to the mentioned thread. Will it work in a normal TC as well? I want to test it on 8x10. I have lots of that size so I can aford to try out with it.
you can always cut the paper into strips
and bracket your exposure ;)
don't forget a good paper negative looks "thin"
I have loaded two pieces of paper and I will try tomorrow. I'll propably a test strip like you do when determining the exposure time for enlarging. I will expose with increments on the same piece of paper. Any guidolines on iso rating for portriga speed grade 2 paper? I'll let you know. Sorry Joe for hijacking your thread. I will start a new one when I will show the results.
I know the old Agfa Portriga Rapid (fiber) had "Agfa" written all over the back -- don't know about the RC paper.
Originally Posted by Peter de Groot
I forgot about this thread, nice to see some activity.
Peter, regarding rating the paper's speed, I did some careful experiments this year and found that with freshly mixed paper developer (Ilford's Universal paper developer) mixed at 1:15 and maintained at a temperature of 68f, I can rate the grade 2 Arista RC paper at an EI of 12.
Prior to this, I was apt to refresh a used batch of developer, and not be too careful as to its temperature (as in, toss the plastic container in the microwave for 30 seconds and let it go at that), and thus was rating the same paper at around an EI of 3. This was in my garage-based darkroom, where 9 months out of the year it's likely to be colder than room temperature.
Once I started my portable processing box project I had to be more consistent with developing, since I can't develop by inspection using this box, and thus had to eliminate some variables in the process, which was how I found the EI=12 rating with 68f fresh chemistry.Your mileage may vary.
I suppose you already figured out that you have to trim about 3mm off the long edges of 8x10 paper to get them to fit into 8x10 sheet film holders.
Good luck and hope to see some results.
Indeed I did. Oh wait I had to trim a couple of mm of the short edges so the flap could close again. Well I shot to pics and they turned out ok. I will post pics in a couple of days. (have to work tomorrow). I shot one at ten second f=8 and the other at 20 sec.
Can you explain what EI means? I still go with Iso for sensitivety.
When I want to make a positive from the paper negative what should I do? Just contact printing under enlarger and expose for a good amound of time?
Glad to see some activity on paper negatives. I like them a lot in large format cameras and are always amazed about the quality of the contact prints. Makes me feel like Fox Talbot. :) I use Ilford MGIV-RC with a yellow filter (Wratten #8) and rate the paper at EI 3, but I don't flash or fog the paper at all. For development, I use Dektol 1+8 and develop to a Dmax around 1.2. The filter and the dilute developer control the contrast nicely.
I never had an issue with the filter showing in pinhole photography, and judging from the calculations, it shouldn't. The filter is just too close to my pinholes, which are around f/256.
Ok I have read a little bit about EI values but only corresponding to iso 100. I shot my paper negatives yesterday at 10 and 20 seconds exposure at F 8.0 so where does the ei story come into this? I come to an Ei of 6,4 and 3,2 but that is assuming an Iso of 100. I don't think that is correct so wich mistake am I making?
Originally Posted by Peter de Groot
There is no magic here. In very simple terms: it is an ISO speed when the speed test is conducted according to the ISO standards, and it is an exposure index (EI) when it satisfies your personal workflow. For example, an ISO 100 film (box speed) may be exposed as EI 64 to create the desired shadow densities. Then you simply say: "I rate this ISO 100 film as EI 64".
Strictly speaking, we should say ISO 100/21° by the way, because the ISO speed is a combination of the ASA speed (100) and the DIN speed (21°). Consequently, ISO 100 is not quite correct. It should be ASA 100 in this case, but dropping the DIN speed from ISO is a common simplification.