Densitometric tests uploaded. Home made densitometer.

Hello again, Ramiro. To add some legitimacy to Ramiro's machine, I've uploaded an old spreadsheet from when I was corresponding with Ramiro when he began looking into building his own densitometer. I notice that the spreadsheet was first created in 11/2002 and was compiled from sample negative strips that Ramiro sent me to run on my Macbeth TD920 as a confirmation of some of his initial baselines. I thought it was remarkably close in its very first version and certainly capable of doing one's own relative/relevant tests. The path to the comparision sheet is at:

http://www.chibardun.net/~craigclu/ramiro_B.xls

Nice going, Ramiro! I recall a few naysayers as you began this project but you stayed your course and I believe you've succeeded!

Hello Craig and forum:

Nice to meet you again. Thank you very much for encouraging me to do my densitometer. With your help, I think I have now a better machine. Yes, that were very early tests, I do not remember how I did that previous tests ¿Do you remember If I did them with the my densitometer, or using the hand held exposure meter.....I do not remember, I am getting old and the previous test were some time ago :-). I have been several months out of B&W busines but I am back again now. Also I changed from Windows to Linux and I lost your e-mail address. I have found a spreadsheet of our comparison and I send you the graph. Let me know if you remember the details of that test.

I am back again in photonet hearing this marvellous forum.

Hello, ramiro

What type of photocell did you use/ CdS? Silicon?

Thanks,

Jorge

Sorry for the typos, too quick a finger...

Hello, Ramiro

What type of photocell did you use? CdS? Silicon?

Pretty cool! what kind of photo-cell didi you use? what are those 2 resistors on the side of the meter? How did you calibrate it?

too many questions, may be you'd better email me the answers in spanish :)

Hi friends!

Sorry for delay, but lot of work this days. The sensor is a CdS photoresistor MORIRICA MKY 54 C348 I am drawing the schematics. I will announce here when I upload them to the WEB page. Any questions will be apreciated. Ramiro.

Tonight I draw the schematics, I think it is better to post it here instead of waiting to the WEB page. Here It is the simple and cheap densitometer. I will make mora drawings of the mechanics details. I hope you like it.

Ramiro,

I looked at your site. I saw only pictures of your densitometer. Will you also publish little description? I can't see where and how you place a film and maybe tehre are some more information which canc ome handy.
It is a great work and I like to make my copy of yours as well. Thank you!

Ok, let me some more time and I will make drawings showing more building datails. I hope you can do the densitometer without any effort. This is a prototipe, sure you can do it with diferent photoresistors. It is a matter of a bit of experimentation.

Ramiro.

Sorry, I forgot to say that negative is placed below the lamp, over the hole.

Sure Ramiro,

it would be great help to all of us, I believe. I was dreaming to make my development more precise, but never had enough money to buy real densitometer. Do you need to calibrate it with real one when you make one like you did?

--
richard vanek
http://piskoftak.com/

Ramiro, see you are using a opal lightbulb for your densitometer, have you tried using a different light source? The neg goes over the little hole I think, so a smaller light source (such as a diffused LED) could work?

Hi again:

For Richard and Pablo.

Densitometer calibration is made by comparation with a step wedge. I bought a really cheap one from Stouffer. You need to recalibrate it from time to time, so it is a good idea to buy one of this. It is also useful for knowing exposure range of papers. There are some issues that need to be solved with the home made densitometer. Densitometer readings are affected by voltage changes in the main 220 V line, due to diferences in light power of the bulb. I do not know if a LED diode can be used, because CdS cell needs plenty of light to work. It will be better using a better power supply, transformer, rectifier and some chip for stabilice voltage. Also, it is needed a warm up period of around 15 minutes. It is a good idea that more people build it and experiment to improve the machine.I know it can be improved very mucha, but as I am a lazy boy and it works reasonable well, I have not experimented anymore. If the 40W bulb can be changed, It will be a very good idea, cause bulb heat is bad for negative.

We will keep in touch. I am drawing the mechanical details.

Ramiro.

Ramiro

Two suggstions relative to lamps:

- Use a silvered, photoflood style one. This way you can place it farther from the negative.

- Modern LEDs, as the 3W Luxeons, may give you enought light for the CdS without any heath.

Thanks Jorge. I would like to use that LED, it will be better than the bulb, smaller and colder. I am going to see what I can find here.

Thanks.

Ramiro

I would go for a Star/O one.

If you cannot get the Luxeons retail in Spain, I've made international purchases from these two sellers:

http://www.markhannahsurplus.com/leds.php

(nice service)

http://anlighten.com/shop/default.php

(better price if they are in stock).

Good luck,

Thanks for the links, I will study them, and after searching in Spain I will make a decision.

Many thanks.

Sorry for my primitive english.

For tose in the United States a Photocell with the same specifications as the Moririca MKY 54 C348 is sold by Mouser Electronics as a XICON model Mouser catalog number 338-54C348.

Jim