Double exposure times for high-contrast filters? Not mine.

[BetterSense]

So it looks like that paper is about grade 2.5-3, if I read it right.

I see how the 21-step wedge is used to measure the range of the underlying exposure, but is
this all I need? Because I don't quite understand where the thirty-one-step exposed wedge underneath the 21-step wedge comes from. It seems like I need a 31-step wedge to contact-print onto my paper to start with, to duplicate what is depicted in that figure.

 

[RalphLambrecht]

You need a 31-step transmission tablet in your typical negative format to enlarge it (mine is 4x5, which is also useful for other tests where contact printing is the way to go). If you don't have a densitometer, you also need a 21-step reflection tablet to measure your results.

In the example of my previous message, the target highlight and shadow densities (step 2 and 20 on the 21-step tablet) are produced at step 23 and 14 on the test print (31-step tablet). This makes a difference of 23-14=9, which is equal to 0.9 log exposure range, because each step on the tablet is 1/3 f/stop or 0.1 log exposure apart. In the attached table, you'll find that a log exposure range of 0.9 is equivalent to a paper contrast of roughly ISO 3.0 (0.88 would be exactly 3.0).

 

[Tom Kershaw]

You need a 31-step transmission tablet in your typical negative format to enlarge it (mine is 4x5, which is also useful for other tests where contact printing is the way to go). If you don't have a densitometer, you also need a 21-step reflection tablet to measure your results.

Could you comment on using a 4x5 transmission tablet as an in-between if your typical negatives are 6x6 medium format or 8"x10"?

Tom.

 

[RalphLambrecht]

Could you comment on using a 4x5 transmission tablet as an in-between if your typical negatives are 6x6 medium format or 8"x10"?

Tom.

I think the largest available are 4x5. Not quite sure what you mean with in-between. In your case, I would get one in 6x6 and 4x5.

 

[ic-racer]

A quick and dirty way to read these 21 step contact prints is to just ignore the one that is 'almost white' and ignore the one that is 'almost black.' Then just count the number of gray steps between them and multiply by 15 to quickly approximate the ISO-R.

 

[RalphLambrecht]

A quick and dirty way to read these 21 step contact prints is to just ignore the one that is 'almost white' and ignore the one that is 'almost black.' Then just count the number of gray steps between them and multiply by 15 to quickly approximate the ISO-R.

Not quite as accurate, because somewhat subjective, but yes, that works too.