Support our Sponsors, they keep FADU free:   AG Photographic   Keyphoto   The Imaging Warehouse   Process Supplies   RH Designs   RK Photo   Second-hand Darkroom Supplies   Silverprint Ltd

Notices

Go Back   Film and Darkroom User > General discussions > Photography in general

  ***   Click here for the FADU 2015/2014 Yearbooks   ***

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 6th December 2021, 04:37 PM
Terry S Terry S is offline
Friend
 
Join Date: Dec 2011
Location: Southend on Sea, Essex, England UK
Posts: 3,162
Default Difference between a test-strip and the print

Having just watched a YouTube video, the person presenting, recommended using the same way of exposing the final print, as used during test-strips, rather than a total exposure in one go.

This means, if you did 5 second increments on your test-strip and then decided upon 20 seconds say, you should expose the print with 4 times 5 second exposures, rather than just one of 20 seconds. That way the amount of light on both should be the same.

I'm sure I've tried the above way of working in the past, and found no difference, but of late, and only occasionally, my final prints seem VERY slightly darker than the chosen test-strip portion and NEVER are they lighter.

I use a RH designs timer and my enlarger has a standard full voltage bulb, so there is not a warm up time of the lamp at the start of each exposure, that may have been to blame, but like I say, it only happens very, very occasionally.

Has anyone else noticed this in their printing sessions?

Thinking more about it, it has made me wonder if it was to do with agitation being slightly different between the test-strip and the final print? Or maybe, for whatever reason, the sheets of paper vary in speed VERY slightly and only VERY occasionally?

I last noticed it last week, when I was printing up a negative, to produce a few prints for a print exchange that I belong to. Before that, I can't remember when it last occurred.

It could be one of many variables, but I'm just curious if anyone else has noticed this during printing at all?

Terry S
Reply With Quote
  #2  
Old 6th December 2021, 07:50 PM
Mike O'Pray Mike O'Pray is offline
Friend
 
Join Date: Oct 2008
Location: Daventry, Northants
Posts: 8,412
Default

Terry, I have seen this mentioned before and in theory it sounds sensible to use the same method for both test strips and final print but in practice does the interval method say 3 strips of 4 secs to get to the 12 secs strip differ enough from then using one 12 sec exposure for the final print to make enough of a difference to be detected by the average( that's me ) printer's eye?

I think it was Ralph Lambrecht who said that he can see a 1/12th of a stop difference in a print. I doubt I can but assuming this is the average to good printer's ability then from the fstop tables it looks as if 1/12th of 12 secs exposure is 0.7 secs so even with good "printer's eyes" the difference in say 3 or 4 intervals of 4 or 3 secs compared to one straight 12 sec print has to be more than 0.7 secs to be noticeable so is it more than 0.7 secs? It doesn't seem likely to me

That's sounds to be more of a fine difference than I can see

Mike
Reply With Quote
  #3  
Old 6th December 2021, 11:11 PM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 2,847
Default

Quote:
Originally Posted by Mike O'Pray View Post
Terry, I have seen this mentioned before and in theory it sounds sensible to use the same method for both test strips and final print but in practice does the interval method say 3 strips of 4 secs to get to the 12 secs strip differ enough from then using one 12 sec exposure for the final print to make enough of a difference to be detected by the average( that's me ) printer's eye?

I think it was Ralph Lambrecht who said that he can see a 1/12th of a stop difference in a print. I doubt I can but assuming this is the average to good printer's ability then from the fstop tables it looks as if 1/12th of 12 secs exposure is 0.7 secs so even with good "printer's eyes" the difference in say 3 or 4 intervals of 4 or 3 secs compared to one straight 12 sec print has to be more than 0.7 secs to be noticeable so is it more than 0.7 secs? It doesn't seem likely to me

That's sounds to be more of a fine difference than I can see

Mike
I doubt very much if anyone can see the difference of 1/12th of a stop. Human eyes are not made that way. Possibly if you are using a hard grade, 4 and above you should be able to see the difference of 1/4 of a stop or perhaps 1/6th but 1/12th. Nope.

Try it using the method where you calculate the exposure using the stop method where step increases are by 1/4 of a second you will be able to decide for yourself.
Reply With Quote
  #4  
Old 7th December 2021, 04:28 AM
Uwe Pilz's Avatar
Uwe Pilz Uwe Pilz is offline
Friend
 
Join Date: Dec 2020
Location: Leipzig, Germany.
Posts: 220
Default

Is you switch on the enlarger the bulb needs a short time for getting maiximum bright.

I avoid this error another way: I have a large sheet of cardboard. For my test strip I count with the metronome and cover more and more form the test strip with that cardboard.
It counts, not to have steps between the times but factors. I use thirds of a stop and know the scale by heart: 10-13-16-20-25-32-40-50-64-80-100.

From the test strip I can guess what 1/6 of a stop would look like and this is accurate enough for me.

Last edited by Uwe Pilz; 7th December 2021 at 04:33 AM.
Reply With Quote
  #5  
Old 7th December 2021, 08:07 AM
John King John King is offline
Friend
 
Join Date: Nov 2012
Location: County Durham
Posts: 2,847
Default

Quote:
Originally Posted by Uwe Pilz View Post
Is you switch on the enlarger the bulb needs a short time for getting maiximum bright.

I avoid this error another way: I have a large sheet of cardboard. For my test strip I count with the metronome and cover more and more form the test strip with that cardboard.
It counts, not to have steps between the times but factors. I use thirds of a stop and know the scale by heart: 10-13-16-20-25-32-40-50-64-80-100.

From the test strip I can guess what 1/6 of a stop would look like and this is accurate enough for me.
Uwe, This will not work with accuracy when printing colour. If you print a test strip with a certain filtration then change the filtration by only a small number of units that filtration will alter, by fractions of a second. This is why some timers have 1/10ths of a second dial.

I use a Kodak colour filtration guide where there are filters to assess any changes in filtration. so if the filters suggest the print needs extra units of filtration or indeed less, there is a formula where you multiply the original exposure time by a factor which depending on the colour and intensity of the change can be from 1.1 up to 2.9 which will inevitably give you fractions of a second. Give less or more time than the compound figure suggests will introduce another colour filtration error error.

For example if you make an exposure on a strip of paper and the exposure that looks right, but the colour is shall we say too blue, you may have to subtract 10 units of yellow, the original time will then be incorrect so you multiply that time with a factor of 1.1 (which is given in the set of filters). So if the original time was 16 seconds the new time would be 17.6 seconds. That is not easy to gauge accurately without a timer with fractions of a second and virtually impossible to do without a timer at all.

If the bulb takes a certain time to get to full intensity, this should be equal every time you switch the light on, so will to all intents and purposes cancel that problem out. Again with colour this may present another problem because with age the colour temperature of a bulb will change and you have to all this into any calculation.

Last edited by John King; 7th December 2021 at 08:14 AM.
Reply With Quote
  #6  
Old 7th December 2021, 12:14 PM
Uwe Pilz's Avatar
Uwe Pilz Uwe Pilz is offline
Friend
 
Join Date: Dec 2020
Location: Leipzig, Germany.
Posts: 220
Default

> This will not work with accuracy when printing colour.

Oh yes. I made colour in my younger days, but is decades ago. My hints are for b/w only.
Reply With Quote
  #7  
Old 7th December 2021, 12:47 PM
Dave Hodson's Avatar
Dave Hodson Dave Hodson is offline
Friend
 
Join Date: Oct 2016
Location: Alberta, Canada
Posts: 61
Default

I saw something similar in Fred Picker's videos and in his book "Zone VI Workshop" he wrote "ten one-second exposures will give less density to a print (or negative) than one ten-second exposure". He called it the intermittency effect and was explaining why the clouds were darker on his print.
I'm still learning as a printer so probably wouldn't notice but don't we see something similar with the reciprocity effect on film when calculating exposure? Combine that with the bulb warm up concept that Uwe and John mention above and the idea makes some sense. In the interests of best practices, it might be the thing to do.
Having said that, I don't see any mention of it in Ansel Adams "The Print". He goes with the total time that gave him the exposure he wanted on the test strip.
It's an interesting idea though and something I'd like to understand better. Thanks for posting
Reply With Quote
  #8  
Old 7th December 2021, 04:55 PM
Mike O'Pray Mike O'Pray is offline
Friend
 
Join Date: Oct 2008
Location: Daventry, Northants
Posts: 8,412
Default

Dave it seems to be something that is in theory a fact i.e. enough intervals over a short or shortish final time for exposure and then taking, for arguments sake, 1sec x10 intervals as the equivalent of one exposure at 10 secs will not be the same

However I can't find any kind of experiments that have ever been used to prove what the difference is and under what circumstances the difference become noticeable

However you are right that using discrete times for each strip and then using whichever one gives the best exposure eliminates any possibility of difference

This is easy to do with the likes of a Paterson test strip printer or Ralph Lambrecht's test strip printer where each partition is raised and lowered separately or in Ralph's case the card in moved each time into that part of the printer that covers the sheet but much more difficult to do with a moving card which requires a second card to cover the exact strip previously exposed.

Did Fred Parker give details of intervals and times when he demonstrated the difference?

pentaxuser
Reply With Quote
  #9  
Old 7th December 2021, 06:06 PM
Dave Hodson's Avatar
Dave Hodson Dave Hodson is offline
Friend
 
Join Date: Oct 2016
Location: Alberta, Canada
Posts: 61
Default

Hi Mike
No, he didn't go into a lot of discussion about it. Fred Picker died in 2002 but he was a bit of a legend (to me anyway). I still pick up his Zone VI Workshop book to read through and if you're lucky enough to have access to his newsletters, they're always interesting to read. The workshop was available in DVD (VHS???) that has since found it's way to Youtube and I highly recommend it if you have the time. It's about 3 hours long but it covers a lot.
At about the 2:24 mark, he's exposing a print using multiples of 3 sec intervals (his test strip interval). He mentions intermittency here but admits that he doesn't know anything about it. He also comments that the timer might be out and a bunch of short intervals might not be actually the same as one larger one. Anyway, interesting video and I watch it fairly often.

https://www.youtube.com/watch?v=hNUtaMlPh3I
Reply With Quote
  #10  
Old 7th December 2021, 06:33 PM
Mike O'Pray Mike O'Pray is offline
Friend
 
Join Date: Oct 2008
Location: Daventry, Northants
Posts: 8,412
Default

Thanks Dave, I'll have a look. I too have his Zone VI Workshop book but I have always felt that there was an element of the salesman rather than the impartial scientist in Fred's outlook on matters photographic which I admit makes me wary of some of his statements at times

Mike
Reply With Quote
Reply
Support our Sponsors, they keep FADU free:   AG Photographic   Keyphoto   The Imaging Warehouse   Process Supplies   RH Designs   RK Photo   Second-hand Darkroom Supplies   Silverprint Ltd

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Philips Darkroom Test Strip Printer PVB100 Mike O'Pray Equipment miscellaneous 22 5th October 2018 04:23 PM
Test strip mask from down under JOReynolds Darkroom 10 15th January 2018 08:22 AM
DIY Localized Test Strip Printer Todd Barlow Darkroom 5 28th June 2014 02:48 PM
Help needed on Durst DES 100 Test Print Analyzer CambsIan Darkroom 11 3rd September 2012 07:39 PM
Burgess strip ceilings. vanannan Auctions of Interest 4 18th July 2011 07:17 AM


All times are GMT. The time now is 06:09 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.