Exposing 4x5 and 8x10 without a camera?

Hi all!
I asked that question on DP Review, and I was redirected here because are analog specialists.

I need to expose 4x5 and 8x10 color neg film sheets in medium-ish-gray-like density (Kodak Portra 160). I do have the backs & dark slides, but no camera. I do not want any image on there; just plain and consistent medium-ish gray all over. I need this to be repeatable, and it need to be about the same from 4x5 to 8x10.

Based on the suggestions I got on DP review, I'll add this:
-A lab will be processing these, not me.
-I know the result isn't going to be gray when looking at it, I know about and I'm ok with the orange cast of the neg base
-I may not be the most technical person, but I did learn & work in analog photography before converting to digital
-I do need to do this with a color neg, not a B&W
-I'm not looking to make a filter of any kind
-I work with the break-down processes of the negative material
-The specific density of the neg isn't that important; I'll be able to judge from the tests strips


I am unsure how to proceed, and due to the cost of these materials now a days, I thought I'd ask first!

Here are the options right now:
1- I was thinking backs facing a large softbox in a dark room and:
A- incident metering at the place of the film back. Then, take off dark slide, flash, close dark slide. Setting on light meter: Iso 160 (for an iso 160 neg film), aperture to 1, speed
to 5 sec (so it catches the whole flash duration). Then reduce light of 1 stop. Or put light meter to iso 80.
B- measured at the place of the back on a grey 18% card in reflective, same light meter settings.

2- Expose with my B&W enlarger with a 80A cc filter to correct for the 2900K light bulb. I'd take a sheet and make time-strips of .5 sec or .2 sec to decide on correct exposure.

3- Rent an 4x5 and a 8x10 view camera and point it on a white wall illuminated with flash, work in reflective and correct for bellow extension.

Any thoughts on what could work and what would not? Other, simpler suggestions?
Thanks in advance,
Lodo
PS: English isn't my first language, so please forgive my mistakes.

A regular bulb, on a timer, quite far from the film surface (for example across the room) will give very even illumination and should satisfy your needs. You will need trial-and-error to get the exposure. You have made a 'test strip' under the enlarger before, yes?

Hi!
But then I'd have a color cast... unless I find a 5500k light bulb. Then, this could be a great solution... Do you know if one can plug any type of light on an enlarger timer? (ie: a cc light bulb with a very long power cord plugged into an enlarger timer?)
Might that work? Then, I could do a test strip using the dark slide of my backs.

Lodoiska said:

Hi!
But then I'd have a color cast... unless I find a 5500k light bulb. Then, this could be a great solution... Do you know if one can plug any type of light on an enlarger timer? (ie: a cc light bulb with a very long power cord plugged into an enlarger timer?)
Might that work? Then, I could do a test strip using the dark slide of my backs.

Click to expand...

Find an enlarger you can use. I only has to cast an area of reasonably even illumination over about an 11x14" rectangle, so even small-format enlarger with a good lens should do this. Use the largest projected rectangle of light you can for the best evenness.

Use an 80B or 80A compensating filter (blue) to get your light source back to daylight (color heads usually have 3400K° halogen bulbs; that plus 80B and you're good to go). They are easy to find used in many screw-in sized.

Stop way down and make test strips. You don't even need holders, just position the film on the baseboard (make some guides, since you'll be working in total darkness). It should be flat enough that you won't even need an easel.

Make a bunch of exposures on 4x5 film first and send them in to be processed. Keep notes so you know which exposure is right. Then, use that exposure (and enlarger head height) to expose 8x10 film of the same type. The exposure should be the same if the film is the same, regardless of size.

You could also filter a regular incandescent bulb, but you'd need a larger filter and a lamp housing for the bulb; not impossible. And, yes, you can plug any old bulb into an enlarger timer as long as the timer is designed for the proper voltage. Check the label.

Have fun.

Doremus


www.DoremusScudder.com

rent the camera and shoot defocused lens at a blank neutral wall/subject is the best--best control, no muss no fuss. worth the expense. better to find someone here that is in your area who will help you out with their camera for free...

I only do this sort of thing in the darkroom with ortho film, but even with an enlarger it is surprisingly hard to get the right light level without a shutter. One of the reasons I sometimes mount one of my large format lenses in a Beseler sized lensboard.

If you want repeatable results, use a flash illuminated surface or the softbox. That also takes care of colour temperature. You could make a rough pinhole camera from a cardboard box with a reasonably long 'focal length' - say normal for the format. That gives you an aperture to work with and makes exposure calculations much simpler.

You can test it with strips of 35mm film - no need to waste sheets. Get an old cassette and wind the exposed film into that until you reach the main cassette, then draw out a fresh length. Just tell the lab not to cut the film or make prints

Though with a pinhole of known f-number and a flash meter you should be reasonably close first time.

Yeah, maybe the camera is the best method after all, although I've done a bit of exposing film with an enlarger. It really boils down to the availability. If the OP can't find a camera, then maybe the darkroom option is better, or building a pinhole.

Best,

Doremus

Lodoiska said:

Hi!
But then I'd have a color cast... unless I find a 5500k light bulb.

Click to expand...

Have you looked? http://www.bhphotovideo.com/c/product/808082-REG/Ushio_1000046_BCA_Incandescent_Photoflood_Lamp.html

Wow, thanks for all the answers! Sorry I could not come back sooner; I was away at a workshop with very very little internet acces (I really cannot do much with an iPod when the only connexion available is through an Ethernet cable...!)

I know the simplest answer is to do it with a camera, and even if I do have access to an 8x10 though a local shop, the rental cost would be too much. It would be either the camera OR the negatives

What I do have is an enlager & IC timer; and I must have an 80a or b lying around somewhere. It seemed rather straight forward in theory, but grahamp seem to suggest that it would not be such a good way to go, especially with the regular, non-shutter obturator. Has any other person ever tried it? Doremus? I am wondering why it'd work nicely with paper and not film... Is it the the iso difference that makes it more harder to find the right exposure? If it would, then the 80a/b would cut around 2 stops, making my portra 160 feel like an iso 40. I could further cut the light with a light ND filter...

The other solution that could make sense for me would be to build an 8x10 pinhole camera, as suggested. I have never done it, but there are more than plenty DIY for it on the net, and a flash on a white wall is quite easy to provide.

Thanks ic-racer; I did not know about it. From what I understood, though, for this application it would be too bright. I'd need lots of neutral density to filter it! But it's good to know they exist and are so inexpensive

Thanks again for your help!
Lodo

grahamp said:

I only do this sort of thing in the darkroom with ortho film, but even with an enlarger it is surprisingly hard to get the right light level without a shutter.

Click to expand...

May I ask why you found the shutter so important?
Thanks!
Lodo

Lodoiska said:

for this application it would be too bright. I'd need lots of neutral density to filter it! But it's good to know they exist and are so inexpensive

Click to expand...

Distance can help. The farther the bulb is from the film, the more near parallel the rays will be, resulting in a very even distribution on the film plane.

Lodoiska said:

May I ask why you found the shutter so important?
Thanks!
Lodo

Click to expand...

Controlling consistent exposures using the enlarger timer at <1 second can be a problem, even with a pre-warmed bulb. Even Ortho at ISO 40-80 is significantly faster than paper. With a shutter I can start with the bulb on. Since I have the LF lenses, and I find it makes things easier, that's how I do it when the need arises. I could reduce the light output and try to stay in reasonable reciprocity correction levels. I'm just lazy

Graham

grahamp said:

Controlling consistent exposures using the enlarger timer at <1 second can be a problem, (...)I could reduce the light output and try to stay in reasonable reciprocity correction levels

Click to expand...

Thanks, that does clear out a few things. I looked up the 2 films I want to use; one has a reciprocity failure past 10 sec, the other past 128sec. So, I guess I'll try to go the enlarger way, with a 80A and a 1 or 2 stop neutral density, wich would bring the neg to an ISO 10 or 20. This should give me a manageable exposure time that might be more consistent. If this doesn't work, then it's pinhole construction time for me!
Thank you all for your help!

Lodo