The BTZS Paper Test, Do I compensate for Ilford filters?

[Pere Casals]

(if printing a contact sheet with the same head height)?

Great !!!

I'd recommend you meter the effective Lux you have on the easel before you place a filter or the negative. In this way we always have a solid reference when changing the lens or the head height, you may try to work always with same power on the easel. Me, I dim (electronically) the light power to have always 2 Lux on the easel after stopping the lens, I use the Lux meter for that. A Lux meter is $20, telling 0.01 Lux precision.

later I may vary time or power, but if always starting with a known power all it's easier.

You may spot meter on the projection. Imagine that you place a label in each step of the test contact copies with the Lux.Seconds each step received, if you then if you spot meter on the projection of the negative then you get the Lux.Second and you know the gray level.

There are several ways to do that, with different kinds of exposimeter, the important thing is that you do that in a consistent way. IMHO this is very useful because you may end making 1/8 of the test strips.

Problem with BW is that making test strips is very easy. RA-4 printers had to learn to meter accurately on the easel because making many color test strips was a mess.

[m00dawg]

Great !!!

I'd recommend you meter the effective Lux you have on the easel before you place a filter or the negative. In this way we always have a solid reference when changing the lens or the head height, you may try to work always with same power on the easel. Me, I dim (electronically) the light power to have always 2 Lux on the easel after stopping the lens, I use the Lux meter for that. A Lux meter is $20, telling 0.01 Lux precision.

later I may vary time or power, but if always starting with a known power all it's easier.

You may spot meter on the projection. Imagine that you place a label in each step of the test contact copies with the Lux.Seconds each step received, if you then if you spot meter on the projection of the negative then you get the Lux.Second and you know the gray level.

There are several ways to do that, with different kinds of exposimeter, the important thing is that you do that in a consistent way. IMHO this is very useful because you may end making 1/8 of the test strips.

Problem with BW is that making test strips is very easy. RA-4 printers had to learn to meter accurately on the easel because making many color test strips was a mess.

Awesome thanks for the info Pere! Good to know I might actually be on the right track with some of this! My goal is to better correlate exposure and filters so, to your point on test strips, I can make fewer of those while having an idea of what things will look like without having to do so much trial and error.

Good call on measure the light on the base. I should indeed pick up a lux meter. I'll try my Sekonic too. My phone worked surprisingly well to measure the light falloff - it seemed accurate but I didn't end up doing projection tests so I didn't look too closely.

If I understood you right then I should gather the value of my current setup (I haven't moved anything since the tests) because this correlates the exposure to my test sheets, adjusting for maximum black. Then when I compose with a real negative, I would measure the light to get it to roughly the same exposure. To do that accurately, it would be good to use a clear part of the negative or a clear negative so I account for base fog as well, correct?

Once I've done that, I then have an idea of the exposure adjustments required for each filter as well as a guideline for how the filters would affect the contrast.

Glad you mentioned RA-4. I'm a ways away from that (though something I'd like to do one day) and was wondering how folks deal with making test strips in color. That seemed rather daunting given you also have to account for the white balance stuff.

[Pere Casals]

To do that accurately, it would be good to use a clear part of the negative or a clear negative so I account for base fog as well, correct?

For the moment, I'd suggest next starting procedure with the smartphone, later you may refine your methods with refined meters, lux meters, etc.

0) Make another calibration with filters 4-5 at twice the exposure.

1) You have not moved the head, ok, take your smartphone and meter in the center without filter, this will be your base light power and exposure time, same than in the tests, say 15s, you expose 2x time for filters 4-5 ! say 30 seconds.

2) Now place the Stouffer wedge in the negative carrier, with no filter. Just take the phone again and meter the light power in each patch, write down a table step vs "lux". The smartphone lux are not real, but a good reference.

You are done !!! From know you may predict your densities on paper !


> From now you will use always the same exposure time, (in the future you may change it, but at the beginning for simplicity you keep it always constant).

> Place the enlarger head at the height you want, place the negative without filter.

> Meter with the phone in the spots you want in the projection, imagine you meter in a cheek (face in a portrait), then locate in the table which step (patch) is that exposure, then you may look at each of the test contact copies of the Stouffer what gray level you will obtain.

> Then you may stop more or less the lens (or with a dimmer) to get the gray level you want. For example you want the gray level of patch 18 in the cheek, when you metered the patch 18 on the easel (point 2> ) you had a reading, just adjust light power until the reading in the cheek is the same than when you metered that path 18.

> You adjusted illumination for the ligth greys, now locate your deep shadows and meter with the phone what reading you have there, locate what patch it is in the table. Say it is patch 8.

> Now locate what test contact copy Grade of the Stouffer has the black level you want in the Patch 8.

You are done, you expose 15 seconds (or 30 for 4,5 grades) and you will have, in the cheek and in the shadows, the gray levels you wanted. Bingo !!! with no strip...

Explained it's a bit long, but it can be done in half a minute: Decide what (light greys) Patch you want for the cheek, take the reading in the table, adjust light power until the cheek has that reading. With the adjusted power take a reading of the shadows, locate what patch is in the table (say patch 8). See what Grade has the gray level you want in patch 8. In half a minute you nailed basic exposure and grade.

From here:

> You may also check what gray level you will have in any spot, from the reading, the equivalent patch, and the grade.

> You may modify the exposure times, so you multiply the reading by the proportionality factor before locating a patch in the table.

You will get practice, you will understand the basic mechanism of the darkroom exposure systems, you will have a criterion to get a commercial exposure system.

This is how I started, one year ago...

[m00dawg]

This is amazing! I wish they taught printing using this method way back when I was in high school. Of course back then we had those infamous Nokia candy bar phones so - well before the iPhone and such. Still I've been used to test strips for so long this is extremely exciting. Thank you again Pere!

[Pere Casals]

Let me add 3 warnings,

A) with described method, in point "2>" you mesure the light in the projected patch to know how much light received the paper for that patch, in theory it's the same, but in the projection case you may have some flare added.

You may meter more accurately in the dense patches (#18, for example) by masking all the stouffer but the patch you are to meter. In the thin patches flare is relatively low, but in the dense patches flare may have relatively important depending on your setup.



B) Another warning, the safe light influences the reading, check what the reading increases when opening safe light, so you may close the safelight for then readings, or you may place a Cyan filter on the sensor. Locate well the sensor on the phone, it is not the front camera, sometimes the sensor it is seen and sometimes you have to find it by casting a show on in it while reding the value.

On my (gelatin) Cyan flter I sprayed some 3M Re Mount glue to place it on the sensor for the printing, but you may also use an old phone. I adjusted the screen to make it display only red, so phone light won't expose paper in the developer.


C) Depending on the smartphone, the sensor can be very, very directional, this may deliver inaccurate readings in the corners, check that by tilting the phone, if it is too much directional you may place a thin difusser on the sensor, say a thin adhesive paper label or translucid plastic.

[m00dawg]

Ah thanks Pere!

I'm hoping to try this today. I have to do some house cleaning (boo) but shot some 4x5 practice portraits of the kiddo and am hoping to use one of these to test things out later today. Really excited to give this a go!

[m00dawg]

So right off the bat this is going to be apples and oranges because I used neutral tone paper today (and did my tests on cool tone) but I tried applying some of the methods up above and actually I got the initial exposure really close! I haven't (yet) recorded the lux values of the step tablet on the enlarger. Perhaps I should have because...

The problem I ran into, I think, might be flare or maybe diffraction or something? I cleaned house today and couldn't find my 3-stop ND I usually use in the enlarger which meant I needed to stop down to f32 and f45 (using my 135mm lens - this is for a 4x5 negative) to get the exposure time where I wanted. The exposure was rather close to what I expected given the above test (I know neutral and cool tone work a bit different so I need to do the tests with the neutral paper for sure). But while the exposure was really close, the contrast was waaay off compared to scans of the negatives I made.

This is a portrait and on the scans the backdrop is a nice visible gray with nice separation to the subject (my kiddo) and his dark brown hair and there is good shadow detail and contrast overall.

For the (5x7) prints, however, the exposures that had good detail and shadow in the face rendered a black backdrop. A #1 filter just made the whole thing muddy. #4 was rather awesome but cut out too much - his hair disappears completely into the inky black backdrop as does his ear (which is on the shadow side). Split grading didn't improve things much. I think the only way out for the backdrop was a dodge and burn which I wasn't keen to do on 5x7 and was running low on time anyway.

The prints are decent apart from the backdrop. In fact they look more like what I expected based on how far the kiddo was away from the backdrop. But the scans definitely show a nice darkish gray backdrop. Prints show a black backdrop.

Projecting a BW negative can cause a contrast bump due to the silver, but flare is a reduction in contrast correct? The latter kinda feels like what I'm running into but whoa it seems extreme. Weirdly this only seems to happen with portraits and usually with the backdrop. Landscapes in the darkroom seem much closer to the scans (I guess perhaps because there is less smooth tone like a person's face perhaps)?

EDIT: Forgot to say I can post the photos tomorrow (prints are still drying)

[m00dawg]

I couldn't sleep super well last night while my mind stirred trying to figure this out (and also had a strong storm roll through) so I got up this morning to try out a contact print. Sure enough, the contact print looks much closer to the scan using a #2 filter. It might look a tad better with a #3 but the background is fairly well defined. The enlarged print I like the most also shows just a hint of background but it's still darker.

So yeah it looks like I should finish my testing Namely to see how much flare I'm getting and how that compares to my contact prints, as well as to go ahead and get the lux of each step since that would have proven useful last night.

This morning I chickened out and used test strips since I wanted to see the results of the film border on the backdrop but the numbers I ended up getting were also close to my tests so that's a positive sign! With a bit of refinement and practice on my part I think I can get there!

[Pere Casals]

apples and oranges

Each paper has its speed, like films. In the Ilford datasheets you will find the speed of your paper, tone is also related to the chloride vs bromide mix, and this has an impact in the speed.



Datasheets tell the paper speed in "ISO P" terms, in the example image you see that without filteres speed is P200, with filters 00-3.5 speed is P100, and for filters 4-5 it is P50.

With that paper we see that grade 4 and 5 do deliver nearly the same exact curve !!!


This would give a good start point, but you should make a calibration for each paper you are using.

If you want to spot meter on the projection to calculate exposures and to predict densities then you need accurate procedures. You may check if the predictions are good and refining your methods until your predictions nail the obtained densities.

It can be debated if this is worth or if test strips are straighter. IMHO calibrations and spot metering in the projections help to obtain better results, faster and wasting less paper, but here, clearly, YMMV.

[m00dawg]

It can be debated if this is worth or if test strips are straighter. IMHO calibrations and spot metering in the projections help to obtain better results, faster and wasting less paper, but here, clearly, YMMV.

Oh I'm definitely in the camp of doing metering now that I've had a glimpse of it. Turns out I was chasing flare I think (more on that below) but for some compositions it's hard to find a good place to place the test strip so I have to make big strips or multiple and it still takes some fiddling. So yeah this is the route I'm going. For fiber prints I bet it's even more worth it.

On the note of flare, huh, yeah I guess I have some:



It's bad in the areas that were well beyond max black but even so this sure points to why the background was so much darker on my projection versus my contact print:



The scan was still better than the contact print but not by much and I could have perhaps dialed that in. You can see better definition in the top of his head on the contact print for sure and it just feels sharper. Given the above, now I know why.

Contact print was also way easier to do. As noted earlier I did a test strip but found the right exposure (using the negative mask), made a print and bam, it was pretty much where I wanted it. That flare really got me off track with my projection prints I think.

I finally found my 3 stop ND so tried to make an equivalent projected print with a more open aperture but ended up with the same result. I'll have to perhaps read up on flare but sounds like there isn't really much I can do about that short of getting another lens (one I used for 4x5 is a Schneider Componon S 5.6/135). Or maybe the lens is dirtier than I think it is *shrug*

The BTZS book as I recall talks about flare so I need to re-read those sections as well.