jim_stewart

My quick and dirty formula for the optimum pinhole size is diameter in inches = 0.0015 times the square root of the focal distance in mm. So if I have a 4 inch (100mm) focal distance the pinhole should be 0.0015 times the square root of 100. This is .015 inches or about 1/64 inch.

 

For the exposure take the f/stop of the pinhole camera and divide it by 16. Square the result (multiply it by itself). This is the amount you need to multiply the f/16 exposure time by to get your pinhole exposure. Using the above example we have 4 divided by 0.015 which is 267. Thus our aperture is f/267. Dividing 267 by 16 we get 16.66 and squaring that we get 277. We need to keep the shutter open for 277 times what the f/16 exposure is. If we are using 100 speed film in bright sun our exposure time is 277 times 1/100 or 2.77 seconds. If you are using a tabular grain film such as T-Max go for 3 seconds or so to account for reciprocity. If you are using a conventions film such as FP4 use 5 seconds or so.

 

Hope this helps.

 

Jim

One book on the subject is:

Complete Guide to Cibachrome Printing

 

Authors: Peter Krause, Henry Shull

Format: Paperback (Illustrated), 160 pages

Publication Date: January 1982

ISBN-10: 0895861763

ISBN-13: 9780895861764

 

The original was published in 1960 and the second edition was put out in 1982. I have seen them recently listed for as little as $2.00 on the internet.

 

Although most of my own work is either B/W or color negative, I did Ilfochrome for several years then went to the Kodak R3000 process because it wasn't as contrasty. With the demise of the latter, I will try Ilfochrome again using some paper and chemistry given to me by friends that "went digital".

I find that I need an electric skillet and two trays of room temperature water. The first thing I do is put a piece of Contact paper on the back of the Polaroid print. Then I put it in the electric skillet which is set for 160 degrees and keep it there for about 4 minutes. You will be able to see when the emulsion starts to bubble. Meanwhile, I soak the sheet of paper that it will be put onto in one of the trays of water. When the emulsion has quite a few bubbles, I move it over to the second tray of water and start to work at loosening the emulsion from the back of the print. After I have about 80% of it loose, I start moving it to a sheet of clear film that is larger than the image so that what was the upper surface of the picture is against the film. Once I get it all on the clear film, I take the paper out of the other tray, turn the clear film/image over, and put the image on the paper. They are both wet and you can move the image around. Once I have it where I want it, I use a very soft roller (brayer) to squeeze the excess water out. Be very gentle and start in the middle and roll to the edges. Set it aside for a day to dry and you are done.

A tool that might work for you is a Wheel and Circle Cutter (also known as a fly cutter) similar to Craftsman 64140. This is basically a lathe bit mounted on an arm that you move in or out from a spindle that goes in a drill press. You can adjust the distance from the center to get diameters from 1 to 6 inches.

The Crown Graphic does have a front rise and a backward lens tilt. After the lens has been extended to its working position, you can depress the angled struts from the box to the bed and then the bed will tilt down and lock into place. This gives you a front forward tilt. You will probably use this in conjuction with the lens rise. If you are using a lens longer than 150mm or so you can get a front shift by pushing the tab in the middle of the front standard down and sliding the lens to the side.

 

Jim

I just finished processing four 11x14 prints in a Jobo CPA. The last

print had a very cobalt blue area for the top 2-3 inches all the way

across the print. This blends to white at the very top. The previous

print was of the same negative had no problems. The image under the

blue/white area has very much reduced density although all of the

image is there. This was on the end of the processor next to the

lift. The chemistry was freshly made up. I used 140ml of each

chemical including a short stop. Do you have any ideas about what

could have caused this? Thanks, Jim

One thing that hasn't been mentioned yet is the chemistry requirements. The 8x10 Nova requires 1 liter of each chemical and the 11x14 Nova requires 2 liters. The B&H price is about $5.00 per liter when mixed from a 10 liter kit. I have the CPA which is a rotary processer and use the Kodak chemistry. I mix up the chemistry that I will need for each session. If I mix up 500 ml (which I usually do) I can get 10 8x10s or 4 11x14s using the chemistry as a one-shot. If I save the chemistry and pour it back in the bottle I can get 20 8x10s or 10 llx14s from each 500 ml before the color balance starts to change. When I reuse the chemistry I do use and discard 2 prewets to get rid of the "stuff" that comes off when you prewet. That is the only change I make to the recommended processing. If I just need a couple of prints it is no problem to mix up 200 or 300 ml instead of 500 or 1000. I don't have any experience with the Nova so I encourage others to comment on storing the chemistry in the Nova vs. draining it out for reuse.

Here is another link for building a 4x5 pinhole camera.

http://www.popularwoodworking.com/features/fea.asp?id=1048

You will start to see some vignetting with focal distances shorter than 90-100 mm. The formula I use for determining the size of the pinhole is d=0.0015xSQRT(F) where d is the pinhole diameter in inches and F is the focal distance in mm. Your aperture is F/25.4/d. To get your exposure take a meter reading at f/16 and multiply it by the square of (16/aperture). For example, if your focal distance is 100mm the pinhole diameter will be .015 inches and the aperture is f/262. (262/16)^2 is 270 so you need 270 times as much light as you need at f/16. If your meter reading was f/16 at 1/100 second the pinhole exposure will be 2.7 seconds. This is more than 1 second so you will have to correct for reciprocity in accordance with the manufacturers information.

Since the vertical stripes occur at the beginning and the end of the roll, could there be light leaks where the film comes out of the cartridge?

 

Jim Stewart

Jonathan, The Jobo tanks come with a lid that has a rubber cap. To use them on the processor you can add a magnet to the base. You fill the tank with the appropriate chemical, cap it, then slide it onto the processor base first. When the tank moves to the horizontal position the chemical enters the area where the paper or film is and processing starts. Many get the Jobo lift for their processor. The lift allows the chemistry to be added and poured out of the tank without removing the tank from the lift. In this case the tank has a cog installed on the mouth of the lid. This cog is held by the lift. Once installed, the cog can't be removed and won't allow the rubber cap to be used. If you have such a tank and want to use it for inversion processing get a rubber cork form hardware store or home center (I got mine at Lowe's) and just use it to plug the opening where the cog is.

 

Jim

I have been making Kallitypes using 4x5 negatives and want to start

making bigger prints. My first thought is to make a TMX interpositive

and then to enlarge the interpositive to make the final TMX negative.

Because of the speed of TMX I am expecting fairly short exposure

times. Rather than trying to use mylar drafting film above the

negative to act as a neutral density filter I am wondering if it

would be possible to use my 150mm camera lens on the enlarger and

control the length of the exposure with the shutter. If it is

feasible would using a lens such as the G-Claron give better results

than my Xenar?

 

My second thought is to use a color transparency as the original

image and projection print it onto TMX of the desired size in order

to get a second generation negative rather than a 3rd generation

negative as above with the interpositive. Would the shorter exposure

scale of transparency film present any problems?

 

Thanks in advance for your thoughts on these ideas.

I haven't seen any good books recently either. OTOH, the basics of printing haven't changed much either. Kodak has pdf's available from their website on the RA4 processing of prints. My suggestions are to let a pro lab process your negatives or slides. You can print your negatives in a home darkroom fairly easily especially if you have a JOBO. The home printing of slides in a darkroom is soon to be a thing of the past with the discontinuance by Kodak of their Radiance paper leaving only Cibachrome. Contact me off net if you would be interested in a writeup I did on printing color negatives in the home darkroom several years ago for a camera club I am a member of.

When I made my tubes I beveled the inside edge for about an 1/16 to an 1/8 inch. This makes it very easy to find the corner and grab it.

Can I use calcium ascorbate instead of sodium ascorbate to get the

fine grain effect with Rodinal that Patrick Gainer came up with. The

calcium ascorbate is very readily available in health food shops

whereas the sodium ascorbate is hard to find.

I keep a body (currently an Olympus XA2) dedicated to infra-red. The 87 filter is taped so that it covers the opening in front of the film plane using mylar slide mounting tape. This way I can use the view finder in the normal way. This is important if you use a SLR body. The built in meter is set for EI 32 and the film developed in D76h for 9 minutes.

Regarding the personal darkrooms, I agree with the earlier posters that black and white will be around for years to come. As far as color is concerned, paper and chemicals for printing from negatives (RA-4 or equivalent) will continue to be available for quite a few years because of the commercial processing for the many 35mm and disposable cameras in use. My understanding is that the Fuji Frontier processors scan slides and use that digital information to control lasers that expose their RA-4 compatible paper. This is another reason that color negative printing will continue. Kodak has discontinued the R-3000 chemistry which was used for direct reversal printing of slides. I have been unable to find any of the R-3000 equivalent chemistry being currently manufactured. (The minimum size for the R-3 is 12.5 gallons and it requires a re-exposure to light for the reversal.) At least for now, if you want to make a print directly from a slide the only process that I am aware of is Ilfochrome.

I have mixed Rodinal using the formula in Anchell's book and encountered the same cloudiness. Starting with 200 ml of his solution A, slowly add small amounts of solution B (the Hydroxide). The solution immediately turns cloudy. After about 50ml of the hydroxide has been added the solution finally starts to get clear spots in it. Keep adding the hydroxide a ml or two at a time until it just stays cleared. I usually add 60-80 ml of the hydroxide to the 200 ml of solution A.

 

You didn't say what size kit you mixed up. The 1 liter kit could take over 300ml of the hydroxide. It sounds like you may not have added enough hydroxide.

 

I second the above suggestion to call the Formulary. The folks back there are all knowledgable and very helpfull.

 

Jim Stewart

I agree with the 3'x4' size. I used a combination of elastic and velcro to attach it to the camera. When I did this, I noticed that there was quite a bit of excess material hanging down below the camera so I tapered from the bottom of the camera to the full width of the cloth at about 45 degrees and put a zipper in along the taper.

 

Jim Stewart

Steve Anchell gives the formula for "traditional" Rodinal as 100gm P-

aminophenol HCl and 300 gm Potassium Metabisufulite per liter. To

this is added a 50% solution of soduim hydroxide solution until the

solution darkens. Photographers Formulary uses 50 Gm of P-aminophenol

HCl and 150 gm Sodium Metabisufulite per liter and then adds a

potassuim hydroxide solution until most of the precipatitate

dissolves. Are these formulas equivalent even though one contains

twice the developing agent of the other?

If you use ascorbic acid instead of sodium ascorbate you will have a

blank roll of film when you finish. The acid neutralizes the

hydroxide in the Rodinal and the developer doesn't develop at all.