Test Strip Exposure Intervals

Kirth Gersen · Jan 21, 2019

Next Question.

I have seen various different advices for the exposure intervals for creating a test strip. Ranging from 3 secs each, 5 secs each and the Ilford suggestion of 2,4,8,16 and 32 seconds. Which should I go for first? I will be enlarging 35mm and 6x7 film onto 8"x10" paper.

Thanks

Richard

MattKing · Jan 21, 2019

I use half stops - 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64 ... - if for no other reason than it is easy to remember.
I'm comfortable rounding things off to 3, 4, 6, 8, 11, 16, 22, 32, 45, 64.
I like to accomplish this by sequentially covering more and more of the strip. I accomplish that with the aid of this chart:

grahamp · Jan 21, 2019

If you can learn to work in stops (factor 2), then you will have an easier time when you come to work at different enlargements (a half-stop burn of a corner is always a half-stop from your base exposure). You will probably want an F-stop table to save doing calculations. Ralph Lambrechts's article is available with a web search.

But either method will work.

In practice, if your are enlarging full frame to 8x10 and have consistent negative densities, you will likely get an idea of the basic time, and test-strip around that.

CMoore · Jan 21, 2019

Keep in mind, i am just a hack street-photographer, working with 35mm black and white.....and there are A LOT of WAY Better Photographers than myself on APUG.
There are So Many Different ways to approach this. What age are you.? Time is the enemy of vision. How much does the composition vary.? How big are your test strips.? If they are the size of a coin, you might have a real hard time seeing 2 seconds of difference, Etc Etc Etc
To me they are less of a "Test" Strip and more of a Ballpark...Approximation strip. SOMETIMES there is just ONE obvious choice, but there are frequently more than one "Correct" times for exposure.
The test strip to me is just a tool to narrow the exposure to where i can choose between 17 and 19 seconds from a test strip that looks like it would be pretty good at 15 or 20 seconds.
Then i can make a bigger test strip at just those two exposures, one at 17 and one at 19 seconds. I can get a much better idea, from a bigger piece of paper, that has just One Image on it and hold it next to another same size piece with a different time on it.

M Carter · Jan 21, 2019

I think the time intervals aren't that important - depending on the enlarger height, over time you just get an auto-pilot sense of "1, 2, 4, 6" or "10, 12, 14, 18".

To me the biggest thing has been making a mask that I can slide the paper under at set intervals (like 1/2" to 2"), so my test strips show the same area of the negative vs. spanning across the entire scene. I can pretty much tell which slice of the shot will have the most exposure difference or will be the central focus of the composition, I'd rather see that in test strips.

For lith printing, I just start with a 5x7 and take a wild guess at the whole frame. I can usually find the right lith exposure by the 3rd try.

Peter Schrager · Jan 21, 2019

The day I quit doing test strips and using a full sheet of paper the world changed
Go for a ballpark f stop and time. If your negatives are consistent it becomes second nature

Doremus Scudder · Jan 21, 2019

The problem with making test strips with fixed intervals is that, as exposure time grows, the fixed interval becomes a smaller and smaller portion of the total exposure; big differences in the beginning, imperceptible ones at longer times.

My approach is similar to Matt's above. However, I don't bother with all the complications of f-stop timing (who needs to be dealing with decimals and square roots when printing anyway?). I use percentages; each stripe on my test strip is a certain percentage more than the previous one.

I usually make test strips in roughly 25% intervals, but they are sometimes a bit difficult to evaluate; 25% is almost to close to clearly delineate the stripes. 30% is a good place to start; you can modify later if you wish.

I like exposure times in the 15-30 second range, so my 30% test-strip sequence looks like this:

Total time: (7) - 10 - 13 - 17 - 22 - 29 - 38 - (50) (values in parentheses I use only rarely; the ones in the middle are my standard)
Count: ............. 10 -- 3 --- 4 --- 5 --- 7 --- 9 -- (12)

You get the idea. The sequence is easy to memorize too. For 25%, use the following:

Total time (7) - 10 - 13 - 16 - 20 - 25 - 32 - 41 - (53)
Count: ............ 10 -- 3 --- 3 --- 4 --- 5 -- 7 --- 9 -- (12)

FWIW, I think in percentages for all my manipulations as well: Increases or decreases in print exposure are done in percentages, dodge and burn times as well. These get notated in my printing record and make life a lot easier when I have to scale a print up or down. I just make a test strip and then figure the new manipulation times as percentages of the new base exposure time.

Hope this helps,

Doremus

mrosenlof · Jan 21, 2019

Since exposure increases geometrically, I do my test strips so that each band is 2x the previous. I choose a minimum exposure, say it's 4 seconds. Start out with the whole sheet (strip) uncovered. so in this example I would stop at 32 sec. My enlarger timer beeps seconds. So set the timer for 32 sec, hit start. On the 4th beep cover 1/4 of the strip, 8th beep, cover the another 1/4, 16th, another 1/4 and at 32, the enlarger lamp shuts off.

After developing, it's fairly straightforward to look at the four sections (sometimes I'll do 5, really never need more) and pick the best, or interpolate between the two. There's no "exact" exposure, so I can judge "16 seconds, then maybe another 1/3 stop darker" and 1/3 of the way between 16 and 32 seconds is about 21.

I get to where I want pretty quickly this way.

Bill Burk · Jan 21, 2019

My experience with full sheets has always been “every time I try a full sheet at a guessed exposure” I ruin a sheet of paper and learn nothing.

Peter Schrager, if you mean that your test strips are huge, that’s cool. I would say you can learn a lot by showing more of the print in a test. But if you are advocating for “print without a test strip,” I don’t understand what you’re thinking.

I always do a test strip, (unless I am ruining a sheet of paper). For grade 2 and 3 I figure a third stop gives me decisive steps. I can easily point to a tree and say that’s what I was thinking. And if some part of the picture looks better on an adjacent step, it gives me the support I need to decide more or less exposure, and dodge and burn, and how much. Most of my dodges and burns are a third stop from the main exposure. I like to keep them barely noticeable.

FujiLove · Jan 21, 2019

Reminds me why I love my f stop timer so much.

Maris · Jan 21, 2019

I use a quick and lazy method based on equal time intervals.

After doing some thousands of enlargements for myself and others I can guesstimate an approximate exposure time, say 10 seconds. This prompts me to set 3 seconds on the enlarger timer and by successive exposures (by foot-switch) and a moving card I get 3, 6, 9, 12, 15, 18 second steps on the test strip. So long as one end of the test strip is too light and the other end is too dark the correct exposure must lie between the extremes. If this is not the case I guessed wrong and must redo the test strip.

For much longer (guessed at) exposure times, say 30 seconds, I'll test in 9 second steps.

Doing separate test strips for land and sky in a landscape image is routine.

Very short test steps like 1 second include enlarger bulb filament warm up and cool down moments when the light is mainly red and the enlarging paper can't see it. A test strip done under those conditions which suggests, say 4 seconds, is probably wrong and 3 seconds is more likely to be correct. This problem only arises when enlarging other people's dreadfully thin negatives.

Exposing test strips is fast. It's the 2 or 3 minute wait while they develop to completion that slows things down. This emphasizes the principle that it's good to get things right first time.

And test stripping on RC paper to save time and money while doing final prints on fibre base does not work well; been there, tried that.

Kilgallb · Jan 21, 2019

I go 16, 8, 4, 2 and 2 which yields 32, 16, 8, 4 and 2 which is a one stop sequence. If I want 1/2 stop adjustment add 30% or subtract 30%. Usually the 32 second is too dark or the 2 second is too light. It is a rare negative with five stops centered.

I find it easier to do a one stop sequence then zero in on subsequent test strips with estimating in 30% changes..

I split grade so I do a strip at GD5 and GD00.

Jim Jones · Jan 21, 2019

Doremus has it right in post #7. Even Ansel Adams in The Print: Basic Photo 3 is less logical, although too many people for the past half century have blindly followed his advice without question. People with enough time to think about what they are doing should always question authorities unless the authority is a traffic cop wavering between writing a ticket or a warning. Long ago a young girl asked her father why she couldn't immediately see the photos he was taking. The result (years later) was the Polaroid system

Peter Schrager · Jan 22, 2019

Bill Burk said:
My experience with full sheets has always been “every time I try a full sheet at a guessed exposure” I ruin a sheet of paper and learn nothing.

Peter Schrager, if you mean that your test strips are huge, that’s cool. I would say you can learn a lot by showing more of the print in a test. But if you are advocating for “print without a test strip,” I don’t understand what you’re thinking.

I always do a test strip, (unless I am ruining a sheet of paper). For grade 2 and 3 I figure a third stop gives me decisive steps. I can easily point to a tree and say that’s what I was thinking. And if some part of the picture looks better on an adjacent step, it gives me the support I need to decide more or less exposure, and dodge and burn, and how much. Most of my dodges and burns are a third stop from the main exposure. I like to keep them barely noticeable.

From the Bruce barnbaum book..that's where I learned it. A full sheet of paper and I can nail a print in usually 3 sheets. NO TEST STRIPS FOR ME EVER. seems really hard but I make great negatives and I know my route of approach that I'm looking for. Fancy machines and do dads ain't my thing no more. I know Michael Smith used a music timer in the darkroom
I'll put it anyone here...meet me and show me your prints and I'll show you mine... over been printing this way for close to 10 years now.
There are MANY PATHS ON THE ROAD..CHOOSE ONE AND LEARN IT WELL
IF YOU WANT WASTE YOUR TIME MAKING LITTLE TEST STRIPS PLEASE DO IT BUT IF YOU TRY THE WHOLE SHEET METHOD YOU MIGHT ACTUALLY GO TO THE NEXT LEVEL

Peter Schrager · Jan 22, 2019

Actually Michael Smith was kind enough to share how he made contact prints on his website. He called it a ring around....its more about knowing your materials. Peole who change paper and developer all the time will never know their materials. Stick with with the program and the whole sheet method works
Have you seen Michaels prints..have you seen Bruce barnbaum prints..??? If you haven't then maybe your concept of what a great print can be is lacking.
I've been using foma paper. I know that in WT developer I use the exposure usually runs about f/11 @ 30 seconds. It could go longer or shorter but you CANT CHANGE THE MATERIALS..That's A CONSTANT...then you do the ring around to dial it in. IF YOU USE A WHOLE SHEET OF PAPER YOU WILL ACTUALLY SEE A PRINT....ITS NOT THAT RADICAL AN IDEA. all I can tell you it saves me time in the darkroom and time is our enemy
Because there are only so many days we can print in this lifetime.
Anyone here is welcome to come see me print
Or invite me to their location.

RalphLambrecht · Jan 22, 2019

Kirth Gersen said:
Next Question.

I have seen various different advices for the exposure intervals for creating a test strip. Ranging from 3 secs each, 5 secs each and the Ilford suggestion of 2,4,8,16 and 32 seconds. Which should I go for first? I will be enlarging 35mm and 6x7 film onto 8"x10" paper.

Thanks

Richard

Always go in1/3-stop intervals because f/stop timing is the best way to go and keep records.

RalphLambrecht · Jan 22, 2019

grahamp said:
If you can learn to work in stops (factor 2), then you will have an easier time when you come to work at different enlargements (a half-stop burn of a corner is always a half-stop from your base exposure). You will probably want an F-stop table to save doing calculations. Ralph Lambrechts's article is available with a web search.

But either method will work.

In practice, if your are enlarging full frame to 8x10 and have consistent negative densities, you will likely get an idea of the basic time, and test-strip around that.

or here:

revdoc · Jan 22, 2019

My f-stop method: set the timer for about half what you estimate the time will be, based on past experience. Give the whole strip that much exposure. Cover up one third of the strip and repeat. Cover up another third (2/3 is now covered) and repeat twice.

That gives me three strips of N, 2N, and 4N seconds. I could do 8N as well, but three stops is usually enough for me.

Kirth Gersen · Jan 22, 2019

CMoore said:
Keep in mind, i am just a hack street-photographer, working with 35mm black and white.....and there are A LOT of WAY Better Photographers than myself on APUG.
There are So Many Different ways to approach this. What age are you.? Time is the enemy of vision. How much does the composition vary.? How big are your test strips.? If they are the size of a coin, you might have a real hard time seeing 2 seconds of difference, Etc Etc Etc
To me they are less of a "Test" Strip and more of a Ballpark...Approximation strip. SOMETIMES there is just ONE obvious choice, but there are frequently more than one "Correct" times for exposure.
The test strip to me is just a tool to narrow the exposure to where i can choose between 17 and 19 seconds from a test strip that looks like it would be pretty good at 15 or 20 seconds.
Then i can make a bigger test strip at just those two exposures, one at 17 and one at 19 seconds. I can get a much better idea, from a bigger piece of paper, that has just One Image on it and hold it next to another same size piece with a different time on it.

Too old! 58. Will be trying out my first print tonight, so have not done this befoe. Think I will create 4 test strips out of 1 sheet of 10x8" to start with.

Kirth Gersen · Jan 22, 2019

Thank you all so much for the advice. Dangerous subject as everyone has a slightly different method. My key learning is that standard intervals don't reflect the equivalent change in light. However, I am the sort of person who is prepared to sacrifice some technical accuracy for something that is easy to remember, so I think I will run with the Ilford technique to start with (2,4,8,16 and 32 seconds), which will give me 5 full stops, and adjust my technique as I gain experience.

tezzasmall · Jan 22, 2019

M Carter said:
To me the biggest thing has been making a mask that I can slide the paper under at set intervals (like 1/2" to 2"), so my test strips show the same area of the negative vs. spanning across the entire scene.

Yes! Something that I've only done for about the last year and it DOES help with picking the correct exposure, as you have multiple exposures of the SAME part of the neg / print, rather than exposures for DIFFERENT parts of the picture.

FujiLove said:
Reminds me why I love my f stop timer so much.

YES! YES! YES! The f-stop exposure printed tables, to me at least, are a nightmare to try and use in and out of the darkroom. When I bought my first RH designs f-stop timer, it all made much more sense and it was so easy to use and the gradual exposures in 1/5 of a f-stop at a time seemed so much more logical than just doubling up numbers (which in turn AREN'T giving you the correct f-stop factor that they seem to offer) or referring to the tables etc. They don't come cheap = even secondhand, but they are definitely worth the investment!

Kirth Gersen said:
Think I will create 4 test strips out of 1 sheet of 10x8" to start with.

YES again! This is what I do for the majority of my test strips. It's not too small or too big and you can easily see what the different exposures offer you.

Good luck with your first session of printing.

Terry S

Bill Burk · Jan 22, 2019

I've only memorized the range of third stops from 40 seconds down to 13. If I can keep my printing in that range, I can do it by heart.

I don't even memorize the times themselves only the seconds to count between moving the cardboard over the test strip.

It's a pretty easy series of numbers to memorize: 10, 8, 7, 5, 4, 3

BainDarret · Jan 22, 2019

Peter Schrager said:
The day I quit doing test strips and using a full sheet of paper the world changed
Go for a ballpark f stop and time. If your negatives are consistent it becomes second nature

I found the same thing. It helps if you keep the whole process simple, one paper, one developer and the same enlarger. I haven't made a test strip in decades.

Doremus Scudder · Jan 22, 2019

Part of the confusion in this thread is due to the way we make test strips. Some (like me) cover stripes successively and time additively; some uncover and time subtractively, some use bursts of a fixed time, etc., etc.

Maybe we should add our test-strip-making methods here as well. Here's mine:

I use a metronome in the darkroom for printing (actually, the metronome function on my timers, but I have used good old music metronomes in the past). I get a "beep" every second and simply count seconds. An exposure of (for brevity's sake) five seconds goes like this: "1, 2, 3, 4, 5, off." (I'm a trained musician and counting like this is second nature.)

When making a test strip, I use a third of a sheet, or sometimes a half a sheet of paper to get as much information as needed. Placement is important; I base my exposure on highlights, so I make sure my test strip gets placed where highlights are. I lay down the sheet under the easel blades, cover the lens with a card and start the timer. The timer is beeping at one beep/sec. I uncover the lens and simultaneously begin counting, "1, 2, ... 10...," at the point where "11" would be, I move the card, covering a stripe of the test strip, and start over counting, "1, 2, 3, ...," etc., etc. For a 30% test strip, I count "10, 3, 4, 5, 7, 9, off," giving me stripes with 10, 13, 17, 22, 29, and 38 seconds exposure in roughly 30% intervals.

I find using percentages so much easier than f-stop timing that I wonder why more don't use it. I don't need to figure how to give an extra 1/6 or 1/3 of a stop exposure to anything; I have a scale with more steps (5%, 10%, 15%...) and have learned to use that. 30% is about a third of a stop, 50%, half a stop, 60%, approx. 2/3 stop, but lots easier to figure from base exposure; no tables, no nothing

Best,

Doremus

CMoore · Jan 23, 2019

M Carter said:
I think the time intervals aren't that important - depending on the enlarger height, over time you just get an auto-pilot sense of "1, 2, 4, 6" or "10, 12, 14, 18".

To me the biggest thing has been making a mask that I can slide the paper under at set intervals (like 1/2" to 2"), so my test strips show the same area of the negative vs. spanning across the entire scene. I can pretty much tell which slice of the shot will have the most exposure difference or will be the central focus of the composition, I'd rather see that in test strips.

For lith printing, I just start with a 5x7 and take a wild guess at the whole frame. I can usually find the right lith exposure by the 3rd try.

What did you make the mask from.....cardboard.?
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