Printable View
Does anyone out there know of a way to use a flatbed scanner as a densitometer? It seems that with a standard sheet of known densities and the right program good comparisons could be made if not exact readings. Is there any part of Photoshop that can be used?
Not the answer you are looking for but... I have heard of someone doing exactly this... can't remember where though. Sorry.
I do this with my Epson 2450 and Picture Window Pro. I created a set values I use when I scan by using a step wedge. Picture Window Pro can display values as densities and I use this to read the values. I have only calibrated this for tranparencies, though it should be possible for paper as well - if you have a refective step wedge.
If you have the same scanner as me I can send you my settings, though I would treat them as only a starting point.
Take a look at http://homepage.ntlworld.com/a.mynett/ep2450/2450densi.htm which tells you how to use an Epson 2450 as a densitometer and shows the results. He uses vuescan software which is alot cheaper than photoshop.
Jerry
Generally the normal RGB values don't tell you the densities. The scanning software is designed to adjust those to produce a reasonable range and color balance. But Vuescan has a not very well documented feature which allows you to read the actual densities. You press the Ctrl key and then move the cursor to the desired location. Below the image, where you normally see the RGB values, you find the densities for R, G, and B. Exactly how this feature works may vary from release to release. In the release I'm using, I've sometimes noticed a significant difference between the numbers shown in the preview and after the scan. The preview seems to have a constant increment added to all values. The scan values seem about what I would expect had I used an actual densitometer. With other releases, these preview and scan values were the same, so I assume this is just a bug which is fixed in later releases. Having the actual densities, as opposed to relative densities, is not important unless you are trying to determine film speed.
I do this with a program called Vuescan. It is a scanning software, and, after you scan your preview, you can then hold the control key, and mouse click on different areas of the preview to get actual density values. It seems to be precise, if not accurate as well.
I used this for some film tests recently, and obtained informative results.
Try google, and search for Vuescan. It is shareware, and many consider it the best program for scanning.
Jeff, and to all others: many thanks.
I did a download of the Vuescan software. It gives me a pop-up with 5 reasons why it won't run. I have an older Visioneer 6600USB which is "no longer supported" by the company.
Computers have such great potential and present so much frustration when one cannot get them to communicate with their attachments. Can you imagine having an arm that won't listen to what your brain tells it to do?
Can you imagine having an arm that won't listen to what your brain tells it to do?
No, but I have a mouth that does that...:-)
I'm also curious about the densitometer readings that I see in an Epson 3200. The responses here help alot. But, I'd also like to know what I can do with those densitometer readings? The way I remember the importance of densitometer readings is that they help you set exposures for printing. I see a lot of data provided for the Portra Endura and Professional Polycontrast III paper that I am using from Kodak's website. My hope is that somehow I apply this to determine exposure time and f settings for the enlarger.
Is this a correct conclusion? How do I do that if I can accumulate data from the scanner?