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Dr Croubie
12-15-2013, 05:18 PM
I thought this would have been already asked, but there's only 3 pages in the paper neg forum and I can't see the answer (although I'm sure I'll see it as soon as I've asked such a simple question and feel like an ass about it).

Anyway, seeing as I've just been gifted a jobo and enlargers, I'm getting ready for paper developing. One thing I've wanted to try for ages is a suitcase-based pinhole camera using paper negs. I've done it in high school many many years ago, and from what I remember it was along the lines of 'poke a pinhole in a shoebox, take a photo, develop, adjust your exposure time if too dark or light'.
But this time I want to use real calibrated-sized pinhole (i've got a lot from Skink to use), I've got a real lightmeter (digisix), I can calculate focal length and f/aperture, all I need to know is what to rate the paper in EI terms to calculate exposure times.
For the record I'm using Ilford Multigrade iv paper, in Multigrade liquid dev for now (maybe when that's out I'll try bromophen too).

RalphLambrecht
12-15-2013, 05:35 PM
I thought this would have been already asked, but there's only 3 pages in the paper neg forum and I can't see the answer (although I'm sure I'll see it as soon as I've asked such a simple question and feel like an ass about it).

Anyway, seeing as I've just been gifted a jobo and enlargers, I'm getting ready for paper developing. One thing I've wanted to try for ages is a suitcase-based pinhole camera using paper negs. I've done it in high school many many years ago, and from what I remember it was along the lines of 'poke a pinhole in a shoebox, take a photo, develop, adjust your exposure time if too dark or light'.
But this time I want to use real calibrated-sized pinhole (i've got a lot from Skink to use), I've got a real lightmeter (digisix), I can calculate focal length and f/aperture, all I need to know is what to rate the paper in EI terms to calculate exposure times.
For the record I'm using Ilford Multigrade iv paper, in Multigrade liquid dev for now (maybe when that's out I'll try bromophen too).
witha yellow filter, which will help controlling the contrast in outdoor shots ,I used an EI of 3 for that combination of paper and developer with sucess.:D

NedL
12-15-2013, 06:09 PM
I pre-flash my paper ( search on APUG or F295 for lots of good info about that ) and I too rate MGIV at 3 with a yellow filter, or 12 without a filter. But that is for cameras with lenses. With MGIV the yellow filter can also help control contrast as Ralph mentioned.

For pinhole, I make a series of tests and figure out the bright sun "sunny 16" for each camera separately, for the paper I intend to use in it. It's easy to go from there with a light meter. It does not take long to do this testing... just use little scraps of paper and quickly develop them, adjusting time as you go. I usually find that I'll refine that time slightly as I use the camera. So, for each of my cameras, I only need to remember one number: this one is 20s, another is 45s, another is 1m, and so on.

Also remember that the amount of blue light is what matters most. So late in the day, you might want to add a stop to what your meter says, and similarly you might make adjustments depending on the colors in the scene you are photographing. A couple weeks ago I was at the beach and I forgot to reduce the exposure because there was a huge amount of UV reflecting off the water....

Have fun!

MartinP
12-16-2013, 03:32 AM
The manufacturer of the paper also makes a series of pinhole cameras. For that series of cameras they have a PDF of an exposure calculator (http://www.ilfordphoto.com/Webfiles/2011106152612113.pdf), which can be printed on a normal office printer to help with relating a lightmeter reading to the tiny effective aperture of the pinhole. There is a huge amount of information on the IlfordPhoto site - the datasheet for the paper can also be useful.

Jojje
12-17-2013, 11:58 AM
In his book "Avancerad mörkrumsteknik" from 1988 (available in english) Lars Kjellberg gives masses of information about various papers, including speeds according ANSI. In it he gives speeds between 250-400 depending of filtration for Ilford Multigrade III.

MartinP
12-17-2013, 05:27 PM
Jojje, take care - the units for those speeds may be the ISO paper system these days, or an out of date measurement system of some sort. Harman give a "film"-speed equivalent to ISO3 for MGIV and that seems about right.

RalphLambrecht
12-17-2013, 05:53 PM
Jojje, take care - the units for those speeds may be the ISO paper system these days, or an out of date measurement system of some sort. Harman give a "film"-speed equivalent to ISO3 for MGIV and that seems about right.

Yes, EI3 worked for me when using a yellow taking filterand using Dektol1+2 as a developer. if that still gives you too much contrastuse a higher developer dilution.I've been using Dektol up to 1+8.:D

jnanian
12-17-2013, 06:14 PM
hi dr c..

paper photography can be dependant on the time of day and season
the iso can be said to be variable seeing its emulsion only responds a certain band/s of light.
have fun with your project and notice the time of day and weather / conditions
it will help you determine your exposures.
paper, dry plate, wetplate &c all require the photographer be more actively involved, and imho so much more fun :)

i hope you post your resukts in the paper neg group!

john

NedL
12-17-2013, 11:53 PM
I always forget to look in the groups here at APUG. There's a pinhole group too!

Jojje
12-20-2013, 11:16 AM
Thanks Martin and Ralph I knew there was a catch - I even double checked Kjellberg's figures! ISO-paper system..?
(I almost always use 120-film with my pinholes.)

jnanian
12-20-2013, 11:46 AM
this thread might be helpful

http://www.apug.org/forums/forum62/57908-does-photo-paper-have-iso-rating.html

that same ilford emulsion might also be as fast as iso 25 :)


re paper speed ratings of 200&c
that is relative to paper speed, not relative to the iso of film

mablo
12-20-2013, 11:49 AM
Jojje, thanks for the tip. I just reserved for me the book you mentioned above on our library website (helmet).

Dr Croubie
03-07-2014, 01:09 AM
Well yeah, so I finally got around to trying this out.
0.6mm hole at 200mm gives roughly f/333, near enough to 7 stops down from f/32.
Took the digisix and the suitcase camera out at lunch today, ended up at 2 minutes with ei3, but no filter.
Now I've got a lovely black piece of paper to hang on my wall...

Dr Croubie
03-07-2014, 01:37 AM
Just did another test strip with a B+W 040 4x Orange filter. Same lightmeter reading, same 2 minutes, same (albeit much smaller this time) nicely black piece of paper.

Either these times are up the creek or I've got a massive light leak somewhere...

MartinP
03-07-2014, 07:56 AM
Just to confirm that your paper is ok, try developing a piece straight from the box, without exposing it. After fixing, it should be white. If it has any tone at all then you have a problem with the paper.

Just wondering the obvious, you do realise that the paper must be developed in darkness or with a safelight, and that you have checked your safelight is actually safe??

Dr Croubie
03-07-2014, 02:39 PM
yeah, the paper and the safelight is good (as are the chems), I was enlarging stuff last weekend with the exact same paper.
I'm pretty sure there must be a light leak somewhere in the suitcase, I'll be adding another set of baffles today to see what else I can block out...

NedL
03-07-2014, 03:21 PM
Um this is still MGIV right? 2 minutes for 200mm "focal" length sounds pretty close to right to me. Even if your exposure was off by 1 or 2 stops whole, you'd still be able see a low contrast very dark image. I think some kind of leak is likely. A good test for light leaks is to load a little strip of paper, put the camera out in the sun, then develop!

Dr Croubie
03-13-2014, 06:13 PM
So over the llast week I've totally attacked this thing with aquadhere, styrofoam packing, black construction-cardboard, and a can of black spraypaint.

Last night I did 3 images:
- a test strip with the suitcase in the sun for a full 10 minutes, lenscap-shutter on. Completely brand-new chemistry, I tipped dev/stop/fix all down the drain last weekend when my HDPP came out pink. Test strip came out totally white.

- then another square (a 3x5" ripped in half), with an Orange 040 (4x) filter. Digisix gave me ev9 at ei6 in almost-sunset behind cloud. 8-stops below the f/32-mark (7-stops for f/ and 1-stop for ei) gave me 8 minutes at f/344 at ei3 (ie, NOT taking the filter factor into account). Test came out almost completely white again, so I started suspecting the brand new chems. Fogged a strip in front of the safelight (10cms for 10secs usually give a nice mid-grey fog) and that came out greyish so the chems were fine. When it was fixed and I turned the lights on I could just see a tiny faint of grey that would have been a bright reflection off my car in the sun.

- So last one, the other half of the 3x5, I took the Orange filter off, got the same ev9, so did the same 8 minutes (ie, no filter factor and no filter), and got a very nice shot of a tree in front of my house. Shadows were almost white and the sky was totally burned black, lots of contrast (I haven't scanned/inverted to see how well it looks in positive).

So today I loaded it with an 8x10 and packed it in the car, I'll see what I can take a shot of at lunchtime. As I've got the 040 Orange on again (for some reason I don't have a 52mm yellow, only orange and yellow-green) I'll take it 10-stops below the f/32 ei6 reading (7-stops for f/, 1-stop for ei3, then 2-stops for filter) and see how i go. Or should I use a different filter-factor because it's MGiv and has a weird curve?

(if this works I've got some 11x14 MGiv and HDPP coming from B+H, this thing could turn out to be a fun suitcase)

Dr Croubie
03-13-2014, 06:50 PM
ps, just re-reading all the posts again. So maybe I did the test last night a bit too close to sunset and there wasn't enough blue light around and the Orange filter took out what little there was. So if I do a shot today at almost exactly midday, what's a good starting point for the filter-factor? It's a bit grey and cloudy today, but it might clear up to blue skies in the next 3 hours...

NedL
03-13-2014, 08:14 PM
My experience with orange filters is that they require a very very long exposure with paper negatives... way higher filter factor than for film. For a yellow filter I use a filter factor of 4 ( 2 full stops ). I'm not sure what it is for orange because I gave up on them early on!

But I'm glad to hear you are starting to have success and it sounds like you will dial it in soon!