# Film speed testing question using waybeyond excel sheet

Show 40 post(s) from this thread on one page
Page 1 of 2 12 Last
• 01-31-2013, 01:53 PM
Film speed testing question using waybeyond excel sheet
Attachment 63432Hi All,

Need a little help here. I am using Ralph Lambrech's spread sheet to determine my film speed.

A 21 step wedge was contact printed Hp5+ at f/8 .7 seconds in Xtol 1:1 @20c for the 4, 5.5, 11, and 16 minute intervals.

Could someone who is familiar with this procedure look at my graphs and tell me what is wrong? I am thinking my exposure is still too short as I am missing too many data points in the shorter development times?

I have a macbeth TD500 and I zeroed using the instruments light source. A calibrated step wedge indicates measurements are accurate.

Any help would greatly be appreciated.

Thanks

Attachment 63431
• 01-31-2013, 08:51 PM
pawlowski6132
Wow. When did photography become a freakin science project?
• 01-31-2013, 11:31 PM
Kirk Keyes
Quote:

Originally Posted by pawlowski6132
Wow. When did photography become a freakin science project?

Since 1890, when Hurter and Driffield invented sensitometry and densitometry.
• 01-31-2013, 11:39 PM
Kirk Keyes
I've not used the spreadsheet you have, but it looks to me that you don't have enought exposure on your 4 min time for the sheet to calculate a valid gradient. Note that the 4 min point on the time vs. gradient graph is way up above the over points off the graph. It looks like that point is calculated to equal 1.90 gradient. We all know it should be less than the 5.6 min gradient.

I suggest rerunning the 4 min test and give the film about 4 stops more exposure to get more steps in the wedge to have usable density.
• 02-01-2013, 01:17 AM
Bill Burk
Looks like your 8 minute time came reasonably close to what I call normal, the curve that most closely fits ASA specifications. Since the spreadsheet shows that near 0.62, that confirms your test is sane.

As Kirk says, 4 stops more exposure would help for the 4 minute test. Next time you do a complete series, I would give 2 stops more exposure to all.

Of course it would have been better if you could see all the data in the highlights. But for darkroom printing, you only need to see what exposures gives you highlight densities around 1.00 to 1.20. You have enough information to make informed decisions about how long to develop your film.

Apart from the 4 minute test, the rest of the gradients look good.
• 02-01-2013, 06:03 AM
pawlowski6132
Hmm. Someone forgot to tell 99% of the brilliant photographers past and present.

The above is totally unnecessary.
• 02-01-2013, 08:35 AM
Stephen Benskin
Quote:

Originally Posted by pawlowski6132
Hmm. Someone forgot to tell 99% of the brilliant photographers past and present.

The above is totally unnecessary.

That's right people. You should know that by now. It's YOU push the button, KODAK does the rest. Duh.
• 02-01-2013, 08:53 AM
pawlowski6132
Sorry
Quote:

Originally Posted by Stephen Benskin
That's right people. You should know that by now. It's YOU push the button, KODAK does the rest. Duh.

You're right. ,sorry people. Fluency in chemistry, sensitometry, electrochemistry, etc is a prerequisite to producing great photographic art.

I'm so stupid. My apologies.
• 02-01-2013, 09:52 AM
sehrgut
tl;dr: stfu, pawlowski

Pawlowski, without people that treated photography as "a freakin science project", you would have NO materials with which to make your own images. No one is claiming that everyone needs fluency in all the scientific disciplines impinging on photography to create great photographic art. What is necessary for anyone to create great photographic art (or workaday snapshots) is that some practitioners have that fluency, to enable the production and improvement of materials.
• 02-01-2013, 01:07 PM