Calibrate a densitometer?

[Matthew Rolfe]

Hi

Is there a simple and easy way to calibrate a densitometer? Any suggestions?

Thanks

[Marko]

Hi Matthew,

The exact procedure depends on the model. But essentially, there are two steps to it:

1. Set the zero point - take a reading with no film, just the light itself and set the scale to zero. If your model comes with separate color channels and a composite one, zero out each channel.

2. Calibrate to a known standard - measure a previously calibrated sample and set the instrument to that value. Normally, it would be the "calibration chip" that originally came with the device, but if you don't have it, you can order a calibrated transmissive wedge from Stouffer and use the densest step for this.

Recommended practice is to turn the densitometer on at least one hour prior to use (to let the light source filaments to heat up and stabilize) and to calibrate before each session.

Hope this helps.

Marko

[D. Bryant]

Hi

Is there a simple and easy way to calibrate a densitometer? Any suggestions?

Thanks

You really need the manufacturers calibration references for reflective and/or transmissive readings to ensure you get consistent readings and to know that your instrument is working properly.

At the very least get a copy of the instruction manual and purchase a Stouffer's calibrated (reflection and/or transmission) step tablet with the proper density range required for calibrating your machine.

Don Bryant

[ic-racer]

A generic calibrated step wedge is a little on the expensive side, but it will have an appropriate density strip that can be used for the "high density" calibration. On my unit it specifies using a density standard around 1.8 log d.

Which densitometer do you have? If you don't have the manual, maybe someone can help you out.

[Matthew Rolfe]

Marko, Don and IC, thankyou for your responses.

I don't have the instruction manual or the calibration chip so I am a bit stuck there. The make and model is;

Melico PhotoLog B/W Transmission

I will have a look for the manual on the internet. I will have a look at the step wedges, prices etc, I hadn't heard of them until you replied to my post, so thanks for bringing them to my attention.

[Marko]

WFIW, I am using Stouffer TP4x5-21C step wedge, which stands for Transmissive Projection 4x5 21-step Calibrated with the Eseco TRC-60D densitometer. Here's the link:

http://www.stouffer.net/Productlist.htm

The important part is to get the Calibrated version (a C version) rather than non-calibrated, even though it is a bit more expensive (but still very reasonable).

I bought my densitometer on eBay for a song, but it came with no manual and no calibration chip. I tried buying the missing parts from Eseco first, but they didn't seem at all interested and at my insistence quoted a truly ridiculous price.

Stouffer, on the other hand, was very reasonable and nice to deal with. I got the manual for free from another member, and it's been working fine ever since.

Marko