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Articles and instructions on making and doing all things photographic

Distance and Exposure

The distance from the light source to your print is important when determining exposure time. I mounted my 20W UVLED exposure unit under the lens holder on my Minolta enlarger so I can easily adjust the height. I can move it up to cover a large print and down for a small one. The advantage of moving the light closer to the print is reduced exposure time. But just how much should I reduce the exposure time, you might ask. Well, here’s how to figure it out. It’s based on the principle that the intensity of light is proportional to the square of its distance from the subject. The inverse square law, IL=1/D2 applies here but keep in mind it’s relative.

For example, if your light is 10 inches from your print it would have 1/100th the intensity as if it were 1 inch away. That’s pretty simple but what happens when we have to deal with real world measurements. Let’s say you were exposing a print with the light source 18.5 inches above the print and you measured the standard exposure at that distance to be 68 minutes. Then you realize that you don’t need to cover such a wide area and you can move the light closer to the print. It looks like you’re getting pretty good illumination when the light is only 11 inches above the print, so how much is the new exposure time? We’ll calculate the exposure factor, a value we’ll call EF, by which you can divide the original exposure time to obtain the new exposure time.

Formula: EF = E12 / E22

Where: EF is the exposure factor, E1 is your original distance and E2 is the new distance

E1: 18.52 = 342.25
E2: 112 = 121
EF = 342.25 / 121 = 2.83

Divide the original exposure time (68 min) by 2.83. That’s about 24 min. See you just saved yourself a bunch of time. If you’re moving the light source away from the print, simply multiply the original exposure time by the exposure factor instead of dividing.

A DIY Centering Guide for Contact Printing Frames

Did you ever try to get a negative and a sheet of paper to stay put while closing the printing frame? I realized it’s a common problem in our craft. This may not be THE fix but the one I came up with is simple and cheap – those are the best kind IMHO.

When a relatively small and light negative and a small piece of paper that may be even lighter lay on a larger sheet of glass any air movement can easily move them around. But what you, the printer, want is for the negative to align perfectly with the paper on which the image is to be exposed. Air movement can be caused by your body moving around the room, ventilation, and often by the back of the printing frame as you put it in place.

Okay, you’re a photographer and chances are good you have one or two pieces of mat board around. Find one that’s at least as wide as the inside width of your printing frame and at least 2 or 3 inches long. Oh, by the way I forgot to mention that your printing frame has to have a split back – most of which are hinged.

Trim the width of the mat board to fit snugly inside the frame’s width. Trim the length to be a little less that the distance from the inside bottom of the frame to the hinge. Next you’ll cut a notch to hold your negative. Just make sure the notch is big enough to stabilize the negative but that part of the negative will extend into the other side of the back. Hopefully you can visualize this. They say a picture is worth a thousand words so check this one out. 

The white area is what I’m talking about.

 

With a little ingenuity, I’m sure you can understand how to modify the concept to exactly fit your combination of frames, negatives and papers.

Here’s a short video to go along with this article – enjoy!

Ilex #5 Flash Synch Repair

My 8×10 Calumet View Camera is a real workhorse. It came with a 14 inch Commercial Ektar f6.4 lens mounted in an Ilex #5 shutter. It produces great images but there is (was) a problem with the shutter. My first portrait session in the studio using flash was a little embarrassing because the flash synch didn’t fire the strobes.

I purchased a special synch cord the week before to connect the bi-pin synch terminals to a modern synch cord, so I imagined that the new adapter was bad out of the box. I worked around the problem by firing the flash manually with the shutter open in T mode. When I got everything home on the work bench, the adapter tested good and the shutter didn’t. This story is about how I disassembled and repaired the shutter.

If you decide to go down this road, you will need a clear work space, access to an ohm-meter, a precision slot type screwdriver and a safe place to keep the small screws you will remove. This is definitely not a couch job.

Step One

Determine that the flash synch contacts are actually the problem. Best way to find out is with an ohm-meter.

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Ohm meter connection

With the meter leads connected to the bi-pin posts, the meter set to OHMS and the M-X-OFF switch set to X, press the shutter release. The meter should blink <100Ω for an instant if the synch switch is working properly. If nothing changes on the meter you can be pretty sure the problem IS the synch switch.

Step Two

Remove the trim ring
Remove the trim ring

Set the timer adjustment to 1/50 second, then remove the trim ring. Remove four small screws that hold the trim ring on to the body of the shutter. You may hear the timer spring unwind a little as the trim ring releases the timer adjustment dog. This is not a problem. Lift the trim ring off of the shutter body. You might have to bend the synch select switch and the aperture adjustment tab a little so that they clear the trim ring.

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Lift the trim ring off of the shutter body.

It’s probably a good idea to remove the front lens assembly at this time, if not sooner. I didn’t have any trouble that would have caused damage, but it’s better to be safe than sorry. Just unscrew it and set it aside in a safe place.

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Remove the timer adjustment ring.

Next remove the timer adjustment ring. Just lift it off and set it aside.

 

Step Three

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Remove the shutter top cover.

Remove the lens mounting collar and shutter top cover. Remove three long screws that hold the top cover on to the shutter body.

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Internal shutter mechanism

 

You can now see the internal mechanism of the shutter. Be careful not to touch the shutter leaves. They are very fragile.

Step Four

Clean the synch switch contacts by first locating the three parts of the synch switch; The sliding contact, the fixed contact and the moving contact.

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Three parts of the synch switch

Note: When the synch selector is in the X position (the correct selection for modern strobe flash units) releasing the shutter will cause the moving contact to rotate a few degrees counter-clockwise as shown in the illustration, closing the synch switch and firing the flash.

ilex5-flash-synch-contact-repair-3Using a contact burnishing tool, clean the switch points under the moving and fixed contacts. Do not use sandpaper. If you can’t access a proper burnishing tool, it’s better to use coarse paper than something that’s very abrasive. The switch points are plated in a thin layer of silver which should be preserved. After burnishing, re-test the synch switch using the ohm-meter. If it tests good, connect the flash unit and actuate the shutter release button. If problems persist, you may need to send the shutter to a reputable repair service such as Flutot’s Camera Repair.

Step 5

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Reassemble the top cover.

Reassemble the shutter. Start with the top cover assembly. Carefully align the synch selector opening on the cover with the opening for the synch selector switch on the shutter body. Ease the cover into place and secure with the three long screws you removed in step three.

Next place the timer adjustment ring on the top cover, aligning as shown in the following illustrations.

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Timer stop tab

Illustration showing the timer stop tab and the notch in the timer adjustment ring.

 

Timer dog alignment
Timer dog alignment

 

Illustration showing the timer adjustment dog inside the timer adjustment ring. Place the ring a little off-center so that it catches the dog, then move it into position, holding it down so that the dog is secured. If you hear the timer unwind a little, try again.

Secure the trim ring
Secure the trim ring

While holding the timer adjustment ring firmly on the top cover, place the trim ring over the adjustment ring, and install one trim screw in the hole nearest the timer dog. Install the remaining three trim ring screws, and the front lens assembly.

Congratulations! You’re done.