Mrhar's Easy Digital Negatives

[MurrayMinchin]

Anybody using Peter Mrhar's Easy Digital Negatives?

I've just started making salt prints and my first attempt at the coating test (tests consistency of density at 256 points on a print) failed miserably. One side is ever so slightly darker than the other. While it's a disappointing result, it's better to know how to coat properly before starting to read step tablets in order to make curve corrections...if not, you run the risk of basing corrections on inadequate/improper densities.

Using brushes so far, but will try a glass rod to see if things get better.

Have made a 256 step gray tablet at max black time, and the last step with a hint of density is #247...that's with an Epson P600, through Harrington's Print tool & Epson Advanced Black & White mode set on 'Light' print density, with yellow set at 75. Pretty close, me-thinks. The dark end occupies most of the print, but that's where the curve correction comes in...which I can do after learning to coat consistently!

Anyways, that's all I've got so far...anybody have experiences/wisdom to share?

Here's his website: http://www.easydigitalnegatives.com/

...and his book: http://www.photomrhar.com/portfolio...ditionhistorical-and-alternative-photography/

 

[MurrayMinchin]

Here's what my coating test (which came out pink-ish when scanned) looked like:

At first I thought it looked pretty good (except for the dust speck) but after looking a bit closer, the right side is a wee bit darker than the left. When the file was read on the EDN website, it showed the classic 'sawtooth' pattern indicating one side being lighter than the other.

To confirm, went back to Capture One and read the cursor #'s for the colour red, and the right side is 229 while the left side is 233.

Darn sensitive test.

Now the question is...was it the salt coat, the silver nitrate coat, or both? Lotsa fun nonetheless

 

[revdoc]

I find that rod coating on a perfectly level surface makes a difference. I have a work surface that slopes slightly downwards to the left, though you wouldn't notice just by looking; if I coat paper for VDB on that surface, the left side of the print will be slightly, but visibly, denser than the right. Therefore, I use a different surface for that task.

On the other hand, if the effect was measurable but not visible, I wouldn't care. That's the issue the EDN coating test... it's more sensitive than me. So it's a matter of judging the importance of the result.

 

[MurrayMinchin]

I find that rod coating on a perfectly level surface makes a difference. I have a work surface that slopes slightly downwards to the left, though you wouldn't notice just by looking; if I coat paper for VDB on that surface, the left side of the print will be slightly, but visibly, denser than the right. Therefore, I use a different surface for that task.

On the other hand, if the effect was measurable but not visible, I wouldn't care. That's the issue the EDN coating test... it's more sensitive than me. So it's a matter of judging the importance of the result.

Hey, thanks for chiming in...you've given spot-on advice.

The darkroom sink slopes to the right to drain, and I've been putting a 3/4" thick piece of birch plywood over a wash tray (with a sheet of glass on top) to coat the paper...therefore, if you're correct...the right hand side of the prints are denser. Will coat another one tomorrow and make sure everything is level and see if it changes things.

I'm okay with 'too sensitive' at this point as it'll tighten up my technique and make custom corrected curves faster to dial in.

Again, thanks a bunch!

 

[jeffreyg]

I was using the glass rod for pt of platinum palladium coating but switched to a brush. If it’s any help I brush the paper with distilled water and wait until it’s almost dry before coating. I get very even coating that way

 

[MurrayMinchin]

...If it’s any help I brush the paper with distilled water and wait until it’s almost dry before coating. I get very even coating that way

Thanks, that's one I'd never heard before and sounds like a good strategy for larger prints. Will keep it in the idea quiver for sure.

 

[nmp]

And if the paper is really not cooperative, add a little T-20 to the brushing water.

:Niranjan.

 

[MurrayMinchin]

And if the paper is really not cooperative, add a little T-20 to the brushing water.

:Niranjan.

Thanks...using Hahnemuhle Platinum Rag for my first round of testing. Figured that would eliminate a few troublesome variables as a beginner to the hand coating game. Will put the Tween 20 idea in the quiver as well

 

[jeffreyg]

Matt
I was using my phone to respond and the edit didn't come up as a choice. The post had "of" instead of "pd" I was talking about Platinum and Palladium. Even though it is pretty humid in Miami, I find I get more even coating when the paper is very slightly moist. It could be that our ac is on most of the time so the humidity in my darkroom is low. Sorry for any confusion.

ABOUT | JEFFREY GLASSER

HOME | SCULPTURE and PHOTOGRAPHY

 

[MattKing]

Fixed it for you

 

[nmp]

Thanks...using Hahnemuhle Platinum Rag for my first round of testing. Figured that would eliminate a few troublesome variables as a beginner to the hand coating game. Will put the Tween 20 idea in the quiver as well

You should be fine with HPR. Salt solution (and subsequently silver nitrate) usually does not have problem with absorbancy - it is almost water-like anyway. If anything the complaint is, it goes go too far into the paper - that's why the need for gelatin etc in the solution. The papers that have heavy surface sizing like some of the traditional watercolor papers are more of a problem, particularly for iron-based processes that tend to have higher solids and greater viscosities.

By the way, the kind of discrepancy you are reporting is really not that bad. I don't know why Mhrar has kept the bar for failure so low.

:Niranjan.

 

[MurrayMinchin]

Bit of an update for those who can't help but slow down and gawk at an accident scene. Hadn't noticed before, but the paper was bowed, or curved after coating, so that could also explain why there was more density on the edge.

Level coating and drying surfaces...check.

Tacky surface on sheet of glass to hold paper flat while coating...check.

Objects placed on print edges to hold paper flat while drying after removing from glass sheet...check.

According to the EDN website (as I understand it) anything above a 3% failure rate is considered poor. My first one had an abysmal 29% failure rate, but the one below is 6% so I consider that good enough for now. There is a faint light blob midway on the right side and some dust specks, so I think without those imperfections the score would have been better. I'll do this test again after playing with images for a while, before getting serious.

Only took a couple days and figure it will pay dividends later. The race is long...

 

[nmp]

Yeah, bowing can be a problem. What is that tacky surface on the glass?

Even the scanner can add artifacts because of cross-reflections. Turn the paper around 90 degrees and see if the relationship holds.

:Niranjan.

 

[MurrayMinchin]

Yeah, bowing can be a problem. What is that tacky surface on the glass?

I used double sided carpet tape...after putting the paper side of each strip of tape onto my wife's pile jacket about 10 times.

Even the scanner can add artifacts because of cross-reflections. Turn the paper around 90 degrees and see if the relationship holds.

:Niranjan.

Good point will give that a whirl, probably tomorrow.

 

[nmp]

I used double sided carpet tape...after putting the paper side of each strip of tape onto my wife's pile jacket about 10 times.

Nice trick. Thanks for sharing.

:Niranjan.

 

[MurrayMinchin]

Nice trick. Thanks for sharing.

:Niranjan.

Not sure of the archival-ness though...there might bits of glue which stay on the paper. The pile fibres were such that no paper fibres came off the back of the print, so maybe its okay. Would have to test somehow, before committing serious work to it.

I asked at a craft supply store for 'sticky pads' and they didn't have any. Pretty sure I've seen pads that could have their stickiness rejuvenated by wiping with hot water. If I find one on the Internet I'll post a link to this thread.

 

[nmp]

At one point I had thought about gluing somehow the other side of the Post-It notes with the sticky side up. Didn't follow thru on it though. The other one I was considering was using one of those sprays that make a re-positionable tacky surface. Longevity is a factor though. Dust will make it unusable over time even if it is not transferring to the paper or the other way around.

:Niranjan.

 

[MurrayMinchin]

Even the scanner can add artifacts because of cross-reflections. Turn the paper around 90 degrees and see if the relationship holds.

:Niranjan.

Thanks for the suggestion.

Gave the print a 180 degree spin and scanned it again. The pattern of errors wasn't mirrored on the left side of the graph this time, and the percentage of error dropped from 6% to 5.28% with the same print.

We have an old copy/scan/fax machine...looks like an upgrade is in order. Might try the copy stand & digital camera route next, to see if that's more accurate before shelling out the money to buy a better designed scanner.

 

[koraks]

Might try the copy stand & digital camera route next

Give it a try, but keep in mind that illuminating a sheet evenly may not be as easy as it seems, especially with the kind of accuracy you're aiming for.

The bees knees is of course a proper densitometer. If you're planning on doing a lot of this stuff, I'd recommend looking into this option.

Good luck on the calibration thing - I don't care to count (and in fact, couldn't) how many calibration sheets I must have printed...enough to make me wake up in sweat at night!

 

[MurrayMinchin]

Give it a try, but keep in mind that illuminating a sheet evenly may not be as easy as it seems, especially with the kind of accuracy you're aiming for.

The bees knees is of course a proper densitometer. If you're planning on doing a lot of this stuff, I'd recommend looking into this option.

Good luck on the calibration thing - I don't care to count (and in fact, couldn't) how many calibration sheets I must have printed...enough to make me wake up in sweat at night!

Thanks for the tips. I've got a 4 light copy stand setup, so will give it Niranjan's spin & redo test to see if it's accurate.

I don't have a densitometer, which is why Mrhar's EDN caught my eye...just scan the test photos and his website crunches the numbers for you. May end up getting a densitometer, we'll see how things go.

Realize I'm going a little too far on the picky factor, but it's early in the game and it's tightening up my technique.

One of the reasons I'm drawn to the hand coating end of the photography pool is that at a certain point you just have to let go. Humidity, temperature, brush pressure inconsistencies, mood, and more can alter a print. That, and there's a point where subtle image textures disappear into the texture of the paper. It's these uncontrollable variables which I believe will allow magic to happen.

 

[nmp]

Thanks for the suggestion.

Gave the print a 180 degree spin and scanned it again. The pattern of errors wasn't mirrored on the left side of the graph this time, and the percentage of error dropped from 6% to 5.28% with the same print.

We have an old copy/scan/fax machine...looks like an upgrade is in order. Might try the copy stand & digital camera route next, to see if that's more accurate before shelling out the money to buy a better designed scanner.

If I understand correctly, the error didn't move with the paper but it stayed at the same side as the scanner. If true, this would mean nearly all your error now is basically induced by the scanner and your coating is pretty good.

What if you add the two scans - you can do that in PS if you have. Rotate the second one back, move it over the 1st layer, align and then give the 2nd layer 50% opacity, flatten. Let Mrhar look at it again.

Most likely you are getting the reflections on the side that has the white cover over the glass. You can may be get better data if you center the print and put a matte black board over it so the reflections are minimized. I do all my scans this way. I think this problem is not any different on high end scanners - I have the Epson 3200 and it's an issue there also.

:Niranjan.

 

[MurrayMinchin]

If I understand correctly, the error didn't move with the paper but it stayed at the same side as the scanner. If true, this would mean nearly all your error now is basically induced by the scanner and your coating is pretty good.

What if you add the two scans - you can do that in PS if you have. Rotate the second one back, move it over the 1st layer, align and then give the 2nd layer 50% opacity, flatten. Let Mrhar look at it again.

Most likely you are getting the reflections on the side that has the white cover over the glass. You can may be get better data if you center the print and put a matte black board over it so the reflections are minimized. I do all my scans this way. I think this problem is not any different on high end scanners - I have the Epson 3200 and it's an issue there also.

:Niranjan.

I did centre the print and covered it with some black material when scanned. Don't have PS.

On the EDN website, when the file of the scanned print was uploaded, there were some larger 'sawtooth' patterns on the right hand side of what should have been a horizontal line. When the 180 degree turned scan of the same print was entered, there was no repeat of that pattern on the left side of the graph.

My assumption is the scanner has a large margin of error and can't be trusted. Will try the copy stand later.

Waiting for silver chloride coat to dry right now. Rummaging around the Internet for frugal densitometers...

 

[gone]

there's a point where subtle image textures disappear into the texture of the paper.

That may be an undefinable factor. Would they disappear evenly across the whole image area? Or evenly enough? I'd go w/ the latter.

Plus

"when the file of the scanned print was uploaded, there were some larger 'sawtooth' patterns on the right hand side of what should have been a horizontal line. When the 180 degree turned scan of the same print was entered, there was no repeat of that pattern on the left side of the graph."

So now you know the errors that can occur simply by turning the paper around. There seems to be a slew of things to ck for something called "Easy" :>}

 

[MurrayMinchin]

...There seems to be a slew of things to ck for something called "Easy" :>}

Yup, like Mt Everest is easier than K2