ISO rating of Ilford Paper?

[Jehu]

I'm trying to test a home made pinhole camera that we will be using for 6 month exposures. I want to check the coverage and distortion that we can expect by doing a quick exposure test with Ilford Multigrade IV 5X7 paper.

The focal length is about 64mm and the hole is 2mm diameter. This gives me an aperture of f32. I just need to know what the ISO rating of the paper for test exposures. I've been looking on line but I can't seem to find anything.

Anyone know where to find this info?

 

[Photo Engineer]

I have made pictures with Ilford MGIV paper using an ISO rating of 25. This is with normal shutter speeds. IDK how the reciprocity would affect you with long exposures.

PE

 

[Colin Corneau]

Efke Positive B&W paper works out to about EI-6, FWIW. You may want to simply try a test on it - the stuff is plentiful.

 

[JohnRichard]

I rated my Ilford Multigrade IV at ISO6. Good and contrasty that way, but I shot for long exposures.

 

[RalphLambrecht]

Efke Positive B&W paper works out to about EI-6, FWIW. You may want to simply try a test on it - the stuff is plentiful.

EI-6 is exactly what I get for Ilford MG-IV in Dektol 1+2 too. However, I rate it as EI-3, using a yellow filter, which I find to be very important, otherwise, I get dead shadows and blocked highlights with my paper negatives. Attached is an example.

 

[removed account4]

fwiw i also use iso 6 ...

 

[RalphLambrecht]

fwiw i also use iso 6 ...

John is definitely someone to trust with this stuff. Go with EI-6 or EI-3 with a yellow filter!

 

[Jehu]

Now I'm a little confused...
My goal is to get a 6 month exposure as per Justin Quinnell's instructions:

This method doesn't use chemical developing. The paper comes out of the pinhole camera and onto the scanner. The scanning will ruin the paper image so you only get one shot at it.

What I'm trying to do right now is figure out what the image size will be on the paper. I may need to change the focal length to cover the full 5X7. I don't particularly care if my test photo turns out good.

If the paper responds like ISO25 film then my f32 shot should be about 1/6 of of second on a sunny day. That seems a little short for a photo paper pinhole camera.

Does this make sense?

 

[RalphLambrecht]

Are you sure there is no chemical development? If yes, count me out, I know nothing about that.

 

[bdial]

The speeds quoted here or in Ilford's datasheet (see http://www.ilfordphoto.com/products/producttype.asp?n=5&t=Photographic+Papers) assume chemical development, which in effect, greatly increases the paper's sensitivity to light.
For your purposes the paper will not respond like film in a conventional (chemically developed) sense, but neither would film.

The size pinhole you need depends on the angle of view you'd like, within some limits any pinhole will cover your 5x7 paper. Sites like pinhole resource http://www.pinholeresource.com/shop/home or perhaps Justin's site should have calculators that help determine pinhole size.
FWIW, f32 would be a really big pinhole, a typical pinhole f number would be 200 something +-

 

[removed account4]

hi jehu

i think your aperture will be wayyyy to big.
http://www.solargraphy.com/index.php?option=com_content&task=view&id=10&Itemid=11
suggests the pinhole should be way smaller than 2mm ... more like a pinprick / a pinhole ...
but i have never done this ( have wanted to though! ) and i have never seen
the instructions posted by justin quinnell ...


to rate your paper, you might want to just to a simple test ...
it is really easy ( easy is good! )
put your paper in whatever camera you own ( a 35mm is ok too )
just cut off a piece of paper and put it infront of the shutter, and close the
camera ... it is that easy

and rate the paper at 1, 3, 6, 12, 25.
you can do a sunny 16 test or
use a light meter if you want be even more accurate with your exposures
just write on the back of each exposure what you rated it at, expose/ process /reload

paper tests are a lot of fun, and kind of addictive
good luck with your tests and your project !

john

 

[removed account4]

The speeds quoted here or in Ilford's datasheet (see http://www.ilfordphoto.com/products/producttype.asp?n=5&t=Photographic+Papers) assume chemical development, which in effect, greatly increases the paper's sensitivity to light.
For your purposes the paper will not respond like film in a conventional (chemically developed) sense, but neither would film.

The size pinhole you need depends on the angle of view you'd like, within some limits any pinhole will cover your 5x7 paper. Sites like pinhole resource http://www.pinholeresource.com/shop/home or perhaps Justin's site should have calculators that help determine pinhole size.
FWIW, f32 would be a really big pinhole, a typical pinhole f number would be 200 something +-

hey barry

years ago i was told ( by kodak ) the iso paper is not relative to the iso for film don't ask me why, i have no idea
... it is like a homonym ... they sound the same but they are different
for example the data sheet for ilford fbmgIV says the paper has a iso of p500 ...


john

 

[bdial]

Hi John,
I know they are different, but like you, don't remember why. The last time I used paper in a camera I rated it at 5, just because it felt right.

For what Jehu is attempting, the speed is not relevant anyway, since he is looking to form an image with brute force, more or less. For that, the speed is probably minus something.

Barry

 

[Photo Engineer]

The ISO speed of papers is quite different than the film ISO rating. They are not related and cannot be compared.

The ISO rating that I gave about (25) was tested in 4x5 sheets in a Speed Graphic with a hand held Seconic spot meter and in small cut sheets in a Polaroid back in an RZ67 set on auto with ISO at 25. The contrast is very high.

I used Dektol 1:3 for 1 - 2 minutes developing for a mid scale exposure.

Enclosed is a scan of the paper negative. I also inverted it digitally for convenience in viewing. My apologies, but this was a test and I wanted to see what it looked like as a true positive.

Remember that Ilford MGIV is orthochromatic but has different contrasts at different wavelengths.

PE

 

[removed account4]

barry,

you are probably right .. its like digging a tunnel with a spoon


================

hey ron

i wish i could do that!
believe me, i have tried to get my paper to
be asa 25 but it thumbs its nose to me ..

it must be something in the air in new york


john

 

[photomem]

I just took two can cameras down here in Memphis which followed those instructions. I have a feeling Reno would be the same. 6 months is way too long. I got crinkled and burned looking paper with a hole burned in the middle. I think it is just too hot to have that type of camera outside for 6 months. Just my observation.

 

[Jehu]

Thanks for all the discussion. I think I'll just guess and hope. The worst thing that will happen is a couple extra trips to the darkroom.

Thanks for the feedback Photomem. I was planning on going from autumnal equinox to winter solstice because the sun will be lower and I won't have to point the camera up to get the highest arc of the sun's trail.

Jnanian,
The pinhole for this process figures to about f32. Justin Quinnell recommends 2mm for a soda can and 0.5mm for a film canister.

 

[Photo Engineer]

Just remember that the reciprocity failure of the paper will offset anything we can give you here.

PE

 

[Kevin O'Brien]

Hi Ralph. Yes it's true, over a period of six months the image actually etches into the paper and if you developed it, it would just go black. You have to scan and save the image. I have images saved in black envelopes but I don't know how long they will last I always scan under safe light.

 

[removed account4]

hi kevin

have you seen this article written by NedL ?
(there was a url link here which no longer exists)

i happened upon something similar a few years ago
when i put something like a solar graph called a retina print
in high carbonate caffenol C .. the image didn't go black and
i was able to fix it without the paper turning white.

if you are wondering what a retina print is, its photo paper, or film or a plate or
whatever you have with emulsion on it, stuck in a camera with a lens ... the lens
is left on B / T for IDK 20mins-2 days and like a solargraph the image is stained on the material.
it doesn't take 6 months ( thankfully ! )
its the original process Nicéphore Niépce used when he invented chemical photography.

i've been doing these retina prints for a handful of years, made ( and sold ) hand made cameras
i constructed for the process ( some small 2x3, some bigger than 16x20 ) ... its a lot of fun.

john

 

[StephenT]

WOW. My results are vastly different from PE's. That makes me think that my calculation of my pinhole f-stop is WAY off. An ISO of about 3 is what seems to work best for me using Ilford MGIV RC. I THINK my pinhole is .3mm. I have a measuring microscope, so I think I will give it a look.

When you get some results, please post back. You have an interesting project.

 

[RalphLambrecht]

I'm trying to test a home made pinhole camera that we will be using for 6 month exposures. I want to check the coverage and distortion that we can expect by doing a quick exposure test with Ilford Multigrade IV 5X7 paper.

The focal length is about 64mm and the hole is 2mm diameter. This gives me an aperture of f32. I just need to know what the ISO rating of the paper for test exposures. I've been looking on line but I can't seem to find anything.

Anyone know where to find this info?

I tested it to be around ISO3 with a yellow filter.

 

[removed account4]

i think everyone's definition of a good paper negative is different
if i was to make a contact print on paper i would want a "thinnish" negative
so the print would fill out, if i was to scan and invert because my paper
had writing on the back, or the negative-paper is too thick to make
a reasonable short exposure for the positive print, i would expose a little more ...
i only recently have used any emulsion ( bottled or on precoated paper ) that was not
excessively expired .. my corporate coated paper emulsions are all about 10+ years expired
bottled emulsion until a few weeks / months ago was all 10-15 years expired too, so i am guessing
while it offers up a nice lower contrast ( due to base fog ) it suffers also from speed loss ..
not to mention i don't really use a full strength paper developer but a coffee based emulsion so it is
doubly loer contrast and required heavier exposure.

i think deciding on a paper - iso / speed is just like figuring out a film speed that works
with your camera, light conditions ( the way you read the light ) and developing methods.

its good to see others using paper ! a medium that is much more fun and finicky than film
( IMHO )