Anyone using a scanner as densitometer?

bvy

Member
Joined
Jul 22, 2009
Messages
3,285
Location
Pittsburgh
Format
Multi Format
If so, what's your workflow? I have a V500 scanner, a calibrated transparency step wedge, and an 18% gray card. I'm looking for a simple way to gauge density in my black and white negatives. I don't need lab precision, but I do want something quantifiable and fairly consistent. (Ideally I know I'd have a wedge or target on the same film base I was testing, but I'm willing to make some sacrifices.)

Thanks.
 

benjiboy

Subscriber
Joined
Apr 18, 2005
Messages
12,001
Location
U.K.
Format
35mm
Don't ask me, I'm so analogue I'm having trouble using my V600 as a scanner
 

Kino

Subscriber
Joined
Jan 20, 2006
Messages
7,888
Location
Orange, Virginia
Format
Multi Format
Without custom profiles for each filmstock, you're not going to get meaningful densities from a simple scan.

Scanners are linear/arithmetic imaging devices; negative densities are measured in logarithmic units.

You'd be better served grabbing one of these for basic density measurements...

https://www.ebay.com/itm/Vintage-Kodak-Color-Densitometer-Model-1/123034003911?_trkparms=aid=222007&algo=SIC.MBE&ao=2&asc=50998&meid=9aaa592d3c5c4bf797c87ae0a67a3c53&pid=100011&rk=2&rkt=2&sd=263343457222&itm=123034003911&_trksid=p2047675.c100011.m1850
 

shutterfinger

Member
Joined
Feb 25, 2013
Messages
5,020
Location
San Jose, Ca.
Format
4x5 Format

Ted Baker

Member
Joined
Sep 18, 2017
Messages
236
Location
London
Format
Medium Format

Its reasonably straight forward as the CCD is mostly linear. You will need to switch to raw, or remove the gamma (which you can do with a calculator). What software are you using? Do you have a step wedge to compare and calibrate? Depending on your answer will try and write some instructions.
 

jim10219

Member
Joined
Jun 15, 2017
Messages
1,632
Location
Oklahoma
Format
4x5 Format
What are you using it for? I had an Xrite 301 densitometer and sold it because I had no use for such precise equipment, but did have a use for the money it brought in and the space it was taking up. These days, I use my flatbed scanner and Photoshop for measuring densities. But I use it for making curves for alternative processes. So in my case, I only needed relative consistency, not empirical accuracy. So long as my results were repeatable and predictable, it didn't matter if my scans were off. For darkroom wet prints, I'm plenty happy with trusting my own eyes. So the best way to go about this will depend on what you're needing to do with this information.
 

Adrian Bacon

Subscriber
Joined
Oct 18, 2016
Messages
2,086
Location
Petaluma, CA.
Format
Multi Format

Yes. It’s fairly straight-forward. You need a way to get the average value of an area of pixels. I use a piece of custom software that I wrote that sucks in 16 bit tiff files and spits out the average r,g,b values of an area that I pass in.

The other part is you need to be able to get the raw linear scan data with no gamma correction applied. Vuescan is good for this if using a flatbed, if using a dslr, dcraw is good.

Once you have that, it’s just a matter of converting from linear to log. Assuming 16 bits, 65535 is 0.0, 32767 is 0.3, 16383 is 0.6, etc.
 

Serg Lavrenchuk

Member
Joined
Jun 23, 2008
Messages
105
Location
Kiev, Ukraine
Format
Multi Format
Links to exl. file are dead ;(
I have in a lab these files stored. If you undestand the system + have 21 step tablet = I could send it to email.
 
You must log in or register to reply here.
Menu
Log in
Register