Densitometer question - X-rite 301 (x)

[willy35]

Someone is selling a very cheap working x-rite 301 (x)

Is that a problem if it is the unit only, there is no Calibration Strip, certification calibration book.

Is it easy to found a calibration step table ?
I see some use http://www.asmetec-shop.de/Foto-tools/Stouffer-Step-Wedges/Stouffer-T2115C.html

Is it worth to buy ($80) ?

Thank you

https://www.yumpu.com/en/document/view/11483228/301-bampw-transmission-densitometer-operator-manual-x-rite

This is this model, without any document / CD

[blue moon]

for that kind of money, it's a great deal.
look around and you should be able to find some sort of calibration strip. If you need me to, I can print a piece of film and send it to you. It would be +/-2% which should get you close enough to get started.

pierre

[willy35]

Thank you Pierre,

I see one guy on internet that is using a calibrated stouffer 21 step, but I have no idea how to calibrate the machine with it, I know nothing about densitometer.

I will try to contact him, hope he can tell me how he does.

[ScreenFoo]

I believe the 301 is just the "Ortho" version of the 361T, which is the one I have.
The calibration is outlined in the manual, should be easier to cal if there's no UV mode.

The cal step on my unit is 2.9 or so.

IMHO if that strip was properly measured with a good densitometer in good cal, you could cal it with that.
That might be a bit of a tall order though, and rather tough to verify.

[willy35]

I wrote to x-rite to know where I can buy the 5 step strip

On the manual the cal is at 3.01, I start to understand but not all 

[willy35]

I am thinking It could not be the machine I am looking for.

Do you know if x-rite we can measure dot gain, so I can make my own RIP linearization ?

Seems 301 was widely use for radio graphic film to check the density. I can not found anything about dot gain.

Which used model of tansmission densitometer is good in our industry ?

Thanks.

[ScreenFoo]

It's just a lot more confusing than it could be, you're on the right track.

Dot percentages can be expressed as densities as well as percentages.
A densitometer will read a Dmax of .301 for a 50% dot.  It will read 1 for a 90% dot, or 2 for a 99% dot.
Your films open area can be nulled (to compensate for Dmin) with that unit for accurate measurements near 1%.

You can find a density (Dmax) to dot (percentage) calculator here: 
https://www.pgo-online.com/intl/katalog/optical-density-transmission-converter.html

It's likely your rip will take either percentages or Dmax (density) measurements.
I'd use the latter.

[willy35]

Thank you ScreenFoo

There is something I still don"t understand about the online calculator.

When I type 0.301 I have the 50%,

but when I type

1, I have 10%

and 2, I have 1 %

How do you found 90% and 99% ?

[willy35]

I may understand

Density 2 --> transmission 1 ---> 100 - 1 --> 99 %
Density 1 --> transmission 10 --> 100 - 10 --> 90 %

 

[ScreenFoo]

I may understand

Density 2 --> transmission 1 ---> 100 - 1 --> 99 %
Density 1 --> transmission 10 --> 100 - 10 --> 90 %

 

You got it.  The percentages we use are almost always absorbance, the opposite of transmission. 
Should have mentioned that, sorry.

Other thing I'd mention is to try to find good resources on pre-press for offset or flex printing.
A lot of that info translates well to screens.

[willy35]

I started to read online but they speak chinese : Demichel/Neugebauer, Murray-Davies equations... 

I got the price from x-rite for
3 different aperture --> $80
5 step certified wedge --> $91  --- 21 steps certified stouffer is half the price, so I will take it.

I will come back when I have the beast, and once I will try to make my first real compensation curve.


Thank again !

[ScreenFoo]

Sure, no problem. 

If I were you I'd hold off buying the apertures, if there's a 3mm installed, that's all I have ever had use for.

Good luck, hope it works out for you.

[willy35]

I received it today.

The aperture is a 2mm, is that a problem ? or is it better to get a 3mm ?

I wonder if I could drill it  - 3mm drill bit is so cheap  Compare to the aperture set...

Thank you !

[ScreenFoo]

I wouldn't try to modify it, but I'm just smart enough to know I'm not very smart about these things. 
Holding calibration and getting repeatable readings would be my priority.

I can't find the PDF I read when I was looking for material on this, but IIRC, you should be OK assuming you're not trying to measure very large halftones.  Maybe 20 LPI (about 8 lines per cm) is where the readings start to jump around a little on mine, so I'd guess maybe 30 LPI/12 Lines/cm is probably about the low end? 

Try it out. 

[willy35]

Hi,

I ordered the proper aperture, you are right, priority is getting repeatable readings, hence buying the proper tools 

I will have my new RIP at the end of this year,

After many hours questioning many suppliers I chose StudioRIP XF - http://www.studiorip.com/
It seems they are beyond competition when it comes to controlling epson printers parameters.


I will come back here when I will make my first reading with the x-rite, I may have some more questions !

Thank you !