New DCG emulsion supplier.

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
Dinesh

New DCG emulsion supplier.

Post by Dinesh »

No, I don't think Saran wrap would work. DCG is mucy too soft for that. The problem is that the emulsion stains easily and any contact with the emulsion leaves a stain which shows on the image.
I remember those plate seperator things. We called them "bippies" at ABNH (gawd knows why!) I thought of packing in those but a stack of plates seperated by bippies could slide in transport. One solution is to use bippies but have the top and bottom plate as just glass. Then wrap the whole thing in tape. Another solution is those corner tabs they used to have for putting photos in albums and again use a blank piece of glass above and below. We have a store called "The Container Store" here in San Diego with all kinds of packaging solutions. I'm thinking of popping over there this weekend.
JohnFP

New DCG emulsion supplier.

Post by JohnFP »

Cool, did you follow procedures outlined by them or your own processing proceedures.
Mark C

New DCG emulsion supplier.

Post by Mark C »

Is 5 minutes typical for 4x5 with the 315M?
JohnFP

New DCG emulsion supplier.

Post by JohnFP »

At the PCG we settled for 10 minutes and exposed for 2 minute and it was a 4 x 5 plate with Dannies 315 laser. I do not think DCG is as critical on exposure time as Silver but it will change processing and color.

Danny, why are you exposing so long? We only used 2 minutes at the PCGGI meeting for a 4 x 5.
Mark C

New DCG emulsion supplier.

Post by Mark C »

Cool, thanks, I was getting worried.
danny bruza

New DCG emulsion supplier.

Post by danny bruza »

its spread out to fit a 8x10 plate
danny bruza

New DCG emulsion supplier.

Post by danny bruza »

10cm x 12 @100mw = 2.41 mins
12cm x 17 @100mw = 4.08 mins
20cm x 25 @100mw = 10.00 mins

JohnFP

New DCG emulsion supplier.

Post by JohnFP »

Danny, I am not arguing your exposure times, but have you done some tests with lower times? If you look at the photo on the PCG group page, you can clearly see that the expanded beam is much, much larger then 10cm x 12 cm (3.9 inches x 4.72 inches). In fact I would say it is closer to 10 inches by 12 inches if not larger. So I am not sure where you got your numbers or if you are radically overexposing. As I stated before, I have found that DCG single beam reflections have a very wide range of acceptable exposure times with with the results being different color shifts and different processing procedures for a desired effect like temperature of baths, amount of hardener in fixer, length in baths etc. I have also found that as you increase exposer time with DCG there is a point where efficiency goes up very sharply then with overexposure it decreases very slowly. So as long as you meet that threashold you get a good hologram and increasing exposure after that time brings the efficiency down very, very slowly.


http://4c-s.org/v-web/gallery/album10/114_1455
JohnFP

New DCG emulsion supplier.

Post by JohnFP »

Ok, again this drawing is not perfect but it portrays the idea. One day I guess I will invest in a real drawing tool like AutoCAD or something but for now, Microsoft paint will have to work.

Use a reference beam that is just off of the perpendicular.
Make 4 card blockers. Even thought the drawing is not perfectly to scale you can see by the colored number where each card can be reused. And being that you can use a nice bright 60 watt bug light, seeing is no longer a problem.
Calculate your estimated exposure time from the approximate energy that your particular DCG formula requires. Cover the plate which is above a white card as in Exposure1. Make that first exposure 25% less then the estimated exposure time. Move to the next set of cards and cover plate as in Exposure2. Make that exposure at the estimated exposure time. Move to the third set of card which is actually the second set reversed and expose for 25% greater then estimated time. Then finally use the first set of cards for the fourth exposure and expose for 50% greater then estimated time. Process.

This should give you a nice starting point and if the brightest part of the hologram is at either end. Repeat the process using that ends exposure time as the minimum or maximum of the next set depending which end it is on. In other words if times were 45 seconds, 60 seconds, 75 seconds and 90 seconds and the 45 seconds resulted in the brightest hologram strip. Repeat the strip process using 23 seconds, 30 seconds, 37 seconds and 44 seconds.

With this process, which is not my original idea just something I was taught many years ago and is readily available in many readings, you should be able to narrow down your optimal exposure time with minimal plate usage.

BTW, this technique is not confined to DCG!
Hope I was clear and the drawing helps.
John


DJ Mathson

New DCG emulsion supplier.

Post by DJ Mathson »

I have allways wondered if it wouldn´t be better to also block of the object light from behind so the object light only hits one strip at a time. Otherwise the back of the hologram will be lit with the object beam at every exposure.
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