rodeo_joe1 Posted December 16, 2021 Share Posted December 16, 2021 With film supposedly coming back into fashion, and with an apparent lack of good processing advice, thanks to unregulated YouTube videos; it seems like there might be a need for an easy way for beginners to check the density of their home-processed negs. Using a calibrated scanner has been suggested in the past, which is fine if you have an expensive stepwedge or transmission greyscale of known densities. But you're probably looking at the cheapest form of densitometer right now - a calibrated monitor. Because the 'density' or brightness shown by a calibrated monitor is easily regulated by the pixel values displayed. For example: I recently posted this in another thread and then thought it might be more generally useful. All you need to do is hold a negative up to the white areas to get a good idea of its base+fog and mid-tone densities. To make the idea more generally useful, here's a spreadsheet table of density versus sRGB pixel values. Easily implemented in any image editor that allows creating custom paint palettes. And if your monitor isn't calibrated - why on earth not? Then here's a little gizmo to help set it to the common sRGB tone response curve. The above needs to be displayed at 100% and the monitor adjusted until the 3 rectangles show a uniform grey. P. S. If your B&W film is regularly showing highlight densities much higher than 2.0D, then you're probably over developing it. 2 Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 16, 2021 Author Share Posted December 16, 2021 Sorry about duplication of image above. It seems that PN's software doesn't allow selective deletion of images during an edit. Link to comment Share on other sites More sharing options...
JDMvW Posted December 16, 2021 Share Posted December 16, 2021 With film supposedly coming back into fashion, and with an apparent lack of good processing advice, thanks to unregulated YouTube videos; it seems like there might be a need for an easy way for beginners to check the density of their home-processed negs. Thanks for the effort, though I'm not so sure most "new" film users are up to it yet. :) 1 Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 16, 2021 Author Share Posted December 16, 2021 Thanks for the effort, though I'm not so sure most "new" film users are up to it yet. :) And that's probably why there are so many "What went wrong?" queries. I'm not advocating the Anal Adams calibrate everything to the Nth degree approach. But knowing what a well-exposed and developed neg should look like definitely won't come amiss. As with most endeavours, you get out what you put in. Link to comment Share on other sites More sharing options...
Sandy Vongries Posted December 16, 2021 Share Posted December 16, 2021 Simpler still, the Kodak Projection Print Scale Link Kodak Projection Print Scale R-26 Cat 155 7248 for sale online | eBay Link to comment Share on other sites More sharing options...
stuart_pratt Posted December 16, 2021 Share Posted December 16, 2021 Thanks for posting this. Can you expand a bit on the rectangles that show a uniform grey? The same grey? And which rectangles exactly. Possibly I’m being a bit slow here but it’s not obvious to me Thanks Link to comment Share on other sites More sharing options...
JDMvW Posted December 16, 2021 Share Posted December 16, 2021 As with most endeavours, you get out what you put in. It's like a sewer then, what you get out of it depends on what you put into it? :rolleyes: I actually have an R-26, but haven't got around to it yet., since I do my adjustments in Photoshop. Link to comment Share on other sites More sharing options...
JDMvW Posted December 17, 2021 Share Posted December 17, 2021 FYI- R-26 1 Link to comment Share on other sites More sharing options...
Sandy Vongries Posted December 17, 2021 Share Posted December 17, 2021 They did quite a good job, and once you figured things out, only necessary for an occasional oddly exposed roll or for a special "perfect" print. Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 17, 2021 Author Share Posted December 17, 2021 (edited) Thanks for posting this. Can you expand a bit on the rectangles that show a uniform grey? The same grey? And which rectangles exactly. Possibly I’m being a bit slow here but it’s not obvious to me Thanks The three 'grey' rectangles marked 50%, 25% and 10% sRGB. They contain 3 squares of alternating complementary coloured stripes, plus a conventional B&W dithered stripe square. When viewed at a distance, all 4 of those inner squares will match the surrounding solid grey rectangle when the viewing medium follows the sRGB tone curve. With any other gamma or tone curve the squares will show a colour tint or shade difference from the surrounding rectangle. If you're only seeing different shades of grey rectangles, then your screen is already calibrated to the sRGB tone curve. Simpler still, the Kodak Projection Print Scale Not really the same thing Sandy. For a start the segments aren't marked in density values, and if mine is anything to go by, it's quite crudely produced and doesn't accurately deliver the timing steps indicated. Plus you still need a uniformly illuminated surface to use it as a visual-comparison densitometer. Say you're looking to check that your mid-grey /18% exposure negative density is hitting the recommended 0.6D to 0.75D + base + fog value (depending on whose book you read or which maker's published curve you look at). What segment of that Kodak thingy is 0.6D? And which is 0.75D? Isn't it just easier to 'paint' a virtual square on your monitor with a value of 137,137,137 and know that its brightness is the same as placing a good 0.6D ND filter over the maximum white of the screen? BTW, the nominal densities of those Kodak R-26 segments, from lightest to darkest are: 0.097D, 0.273D, 0.398D, 0.574D, 0.699D 0.875D, 1.00D, 1.18D, 1.30D & 1.48D So the segments marked '16' & '12' are useful for roughly judging a mid-tone. The rest of those odd density values - not so much! Edited December 17, 2021 by rodeo_joe|1 1 Link to comment Share on other sites More sharing options...
Sandy Vongries Posted December 17, 2021 Share Posted December 17, 2021 The three 'grey' rectangles marked 50%, 25% and 10% sRGB. They contain 3 squares of alternating complementary coloured stripes, plus a conventional B&W dithered stripe square. When viewed at a distance, all 4 of those inner squares will match the surrounding solid grey rectangle when the viewing medium follows the sRGB tone curve. With any other gamma or tone curve the squares will show a colour tint or shade difference from the surrounding rectangle. If you're only seeing different shades of grey rectangles, then your screen is already calibrated to the sRGB tone curve. Not really the same thing Sandy. For a start the segments aren't marked in density values, and if mine is anything to go by, it's quite crudely produced and doesn't accurately deliver the timing steps indicated. Plus you still need a uniformly illuminated surface to use it as a visual-comparison densitometer. Say you're looking to check that your mid-grey /18% exposure negative density is hitting the recommended 0.6D to 0.75D + base + fog value (depending on whose book you read or which maker's published curve you look at). What segment of that Kodak thingy is 0.6D? And which is 0.75D? Isn't it just easier to 'paint' a virtual square on your monitor with a value of 137,137,137 and know that its brightness is the same as placing a good 0.6D ND filter over the maximum white of the screen? BTW, the nominal densities of those Kodak R-26 segments, from lightest to darkest are: 0.097D, 0.273D, 0.398D, 0.574D, 0.699D 0.875D, 1.00D, 1.18D, 1.30D & 1.48D So the segments marked '16' & '12' are useful for roughly judging a mid-tone. The rest of those odd density values - not so much! Shame on me! When I think film, I flash to days of old - you are correct. Not the same. Link to comment Share on other sites More sharing options...
stuart_pratt Posted December 17, 2021 Share Posted December 17, 2021 The three 'grey' rectangles marked 50%, 25% and 10% sRGB. They contain 3 squares of alternating complementary coloured stripes, plus a conventional B&W dithered stripe square. When viewed at a distance, all 4 of those inner squares will match the surrounding solid grey rectangle when the viewing medium follows the sRGB tone curve. With any other gamma or tone curve the squares will show a colour tint or shade difference from the surrounding rectangle. If you're only seeing different shades of grey rectangles, then your screen is already calibrated to the sRGB tone curve. Understand, thanks for the extra input. I'll have a play! Link to comment Share on other sites More sharing options...
glen_h Posted December 17, 2021 Share Posted December 17, 2021 (snip) Not really the same thing Sandy. For a start the segments aren't marked in density values, and if mine is anything to go by, it's quite crudely produced and doesn't accurately deliver the timing steps indicated. (snip) BTW, the nominal densities of those Kodak R-26 segments, from lightest to darkest are: 0.097D, 0.273D, 0.398D, 0.574D, 0.699D 0.875D, 1.00D, 1.18D, 1.30D & 1.48D So the segments marked '16' & '12' are useful for roughly judging a mid-tone. The rest of those odd density values - not so much! Hopefully Kodak gets it pretty close. log10(60/segment number). If you round the numbers you get: 0.1, 0.3, 0.4, 0.6, 0.7, 0.9, 1.0, 1.2, 1.3, 1.5. Even without numbers, though, it gives you a good idea what the densities of a negative should look like. The darker parts, likely sky, should be about as dark as the "2" segment. (Maybe a little darker, but it is hard to judge ones that dark.) Lighter areas 36 or 48, and as noted, mid-tones 16 or 12, maybe to 10. Even easier, if it is all too dark to see though, it is too dark (over exposed, or over developed). If it is all easy to see through, underexposed or underdeveloped. But it gets harder with C41 negatives, even with XP2, which have a much lower gamma. (And, by the way, you don't need nine digits as in your table above.) -- glen Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 19, 2021 Author Share Posted December 19, 2021 (edited) If you round the numbers you get: 0.1, 0.3, 0.4, 0.6, 0.7, 0.9, 1.0, 1.2, 1.3, 1.5. Even without numbers, though, it gives you a good idea what the densities of a negative should look like. As already pointed out, you still need an illuminating surface to use that crudely produced Kodak 'stepwedge'. And you must already have one of those to be reading this post. I.e. a screen, that's also capable of displaying accurate density values, and in colour to boot. (And, by the way, you don't need nine digits as in your table above.) That's just what the spreadsheet spews out as a conversion from density values to a normalised brightness Glen. In fact I think it works to 16 decimal places internally. But the useful number is the integer pixel value to the right of that column. The fractional brightness is just an intermediate step to calculating that. Edited December 19, 2021 by rodeo_joe|1 Link to comment Share on other sites More sharing options...
glen_h Posted December 19, 2021 Share Posted December 19, 2021 (snip) That's just what the spreadsheet spews out as a conversion from density values to a normalised brightness Glen. In fact I think it works to 16 decimal places internally. But the useful number is the integer pixel value to the right of that column. The fractional brightness is just an intermediate step to calculating that. I was in college not so long after hand calculators became affordable to most college students. We all liked to put down 10 digits to every answer, and TAs were good at marking them off, usually with "SIGFIGS". We learned fast. And even years later, notice when there are too many digits. -- glen Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 19, 2021 Author Share Posted December 19, 2021 .... notice when there are too many digits. But what are "too many digits" Glen? 1/255 is an irrational number whose decimal places seemingly go on forever. So I'm not going to waste my time and spreadsheet space working out exactly how many places of accuracy I need to arrive at the correct nearest pixel integer.:confused: That defeats the whole point of using a computer.:rolleyes: Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted December 20, 2021 Author Share Posted December 20, 2021 Is this better Glen? I've just embedded the conversion from density to relative brightness within the sRGB tone curve conversion formula. 1 Link to comment Share on other sites More sharing options...
q.g._de_bakker Posted December 20, 2021 Share Posted December 20, 2021 (edited) But what are "too many digits" Glen? 1/255 is an irrational number [...] From the internet, and verifiably true: "[...], irrational numbers cannot be expressed as the ratio of two integers.". Such as in 1 and 255, and the ratio 1/255? Edited January 15, 2022 by James G. Dainis Link to comment Share on other sites More sharing options...
rodeo_joe1 Posted January 15, 2022 Author Share Posted January 15, 2022 (edited) ... From the internet, and verifiably true: "[...], irrational numbers cannot be expressed as the ratio of two integers.". Such as in 1 and 255, and the ratio 1/255? OK, so technically not an irrational number. But I'll let you work out its exact decimal equivalent. Edited January 15, 2022 by James G. Dainis Link to comment Share on other sites More sharing options...
glen_h Posted January 15, 2022 Share Posted January 15, 2022 0.00 then repeating 3921568627450980 -- glen Link to comment Share on other sites More sharing options...
AlanKlein Posted January 15, 2022 Share Posted January 15, 2022 I have a question maybe someone can answer. First, I don't develop my own film. I send them out to a dip and dunk shop. I also don't use the zone system. I meter for the average or top and bottom ends to be exposed. What I've noticed is that depending on the film, the negative appears to look different between types (Tmax 100, Tmax 400, Tri-x). Is that difference in the film? Or is it just that my exposure are off? They seem to be pretty similar when I scan them with my V850. And I get normal-looking results on the screen. (I have not printed any of them). But looking at some the "whites" and "blacks" on the negatives appear more contrasty or less contrasty. Also, can anyone recommend a screenshot on the web of what normal and abnormal negatives look like for these three emulsions? (Tmax 100, Tmax 400, Tri-x) Flickr gallery: https://www.flickr.com/photos/alanklein2000/albums Link to comment Share on other sites More sharing options...
kmac Posted January 17, 2022 Share Posted January 17, 2022 What I've noticed is that depending on the film, the negative appears to look different between types (Tmax 100, Tmax 400, Tri-x). Is that difference in the film? Or is it just that my exposure are off? They seem to be pretty similar when I scan them with my V850. And I get normal-looking results on the screen. (I have not printed any of them). But looking at some the "whites" and "blacks" on the negatives appear more contrasty or less contrasty. A few variables could be in play there. TriX has a different grain structure and is an older generation film than the other two films. Your "averaging" metering could be out slightly each time ... and the dip & dunk shop may not get the developing exactly right every time. It wouldn't really be surprising if there's differences in contrast, grain size, sharpness, or even exposure. Link to comment Share on other sites More sharing options...
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