Basic Sensitometry, Part 1: The H&D Curve

[@hoggif]

I used to use my scanner as a densitometer and shot zone 1 + zone 8 gray cards with most 35mm rolls (or Z7/Z9 etc for push pull). Great for calibrating the process spot on to eg. adjust developing time a bit due to aging developer. Having a scanner already for scans, no cost. Some software like vuescan at least used to display density readings on preview (haven't checked on latest version).

[@Pixelwaster]

This series is filling in all the missing pieces when trying to learn on your own. Thanks for being a mentor.

[@derekkonigsberg2047]

I greatly appreciate anyone who admits that you're allowed to actually take a scientific approach to any part of the photographic workflow.

[@TheNakedPhotographer]

The great thing about photography is that you can be as scientific as you want to be. Some choose not to and make incredible work, others chart everything and can make incredible work.

[@Bartuul]

Love the fact that all these calculations and graphs could have been made in Excel in like 3 minutes, but You've decided to go with an analog approach. :)

[@TheNakedPhotographer]

Not everyone uses spreadsheets.

[@mikeboudreaux2964]

This was really interesting. The connection between the step wedge (exposure) and film density is the thing that I needed to click. Keep up the good work.

[@johng.arkenberg1070]

Thanks so much for making these videos to introduce photographers to the science of sensitometry. I teach this at a college level and am frequently surprised that more photographers are a) not interested in learning sensitometry, or b) think it is beyond their reach. Your video does a good job of bringing it to the greater public. Some quick notes: - The definition of sensitometry is broader than the one you provided. The original intention from Hurter & Driffield was to measure the sensitivity of a photographic medium to light. However, by the mid-20th century the definition expanded to "the science of tone reproduction." Just want to share this because the science of sensitometry covers not just analog or digital technologies, but also relates these technologies to the human visual system. This is good fodder for future videos. - For shorter exposure times than one second from an enlarger one can bootstrap a large format lens shutter onto the front of the enlarger. - Footcandles were not renamed lux. The metercandle was renamed lux. Footcandles are the photometric quantity of illuminance in non-SI units. Lux is the SI photometric quantity of illuminance and is therefore preferred in sensitometry. There are 0.09 footcandles in a lux. - All films have a shoulder - it's just a matter of exposing and graphing that far out. It's rarely done because the majority of subject luminance ranges are covered in a 10 to 11 stop range. Thanks again for this great video!

[@giuseppeg.8461]

You're an extraordinary teacher of your subject. Incredibly clear explanation. I'm puzzled as to why this series of tutorials of yours doesn't have a view count in the order of the hundred of thousands. Thanks for helping the community through your work!

[@chris-non-voter]

These videos are excellet. Thank you very much.

[@aes53]

This is a great series, and I applaud you for putting it out. I have one comment, though: when you measure the luminous intensity striking your film, you lift up the glass plate and place the meter under it. Understandably, you want to correct for absorption from the glass; however, having it at an angle means the incident light will have loose intensity because some light is split off as a specular reflection and never reaches the meter. It may be too little to make that much difference in the error of your measurement, but you can estimate it from the Fresnel equation.

[@TheNakedPhotographer]

The head is raised very high to minimize the angle at the edges.

[@m00dawg]

I've read up on this numerous times (AA's The Negative, BTZS, a few other books, online) and I never quite got it until now. Thank you for providing this - it was VERY helpful! I've been trying to nail down Adox HR50's development times in XTOL-R (both at box speed and when trying to pull it to 25) and I'm pretty sure I'm over-developing...makes me think this would be a worthy exercise for HR50 and maybe Pancro 400 (which I can't seem to get right in sheets).

[@TheNakedPhotographer]

When I get to gamma and contrast index, you will get a better idea of development adjustments.

[@stealthvanlife6867]

@@TheNakedPhotographer Looking forward to that.

[@dorothykloss5303]

I just received my Kodak Curve Plotting Paper from Ace Photo today, finally! - it cost $14 for shipping and you get 25 sheets for $5.00 The paper is like tracing paper. Looks almost like it's "vintage" paper. the envelope especially. Don't know if Kodak still makes this, or where Ace Photo found it, but it's almost a relic and should be put on a shelf with the Kodak antiques. Thanks for the tip. It also took about 10 days to ship it.

[@luismurag]

Great material. I love Sensitometry.

[@avikkumarroychowdhury2243]

A nice chapter got a scope to revise by this very rare presentations and as of after more than 35 yrs a class room type material nt making none to be only with Texts and to be own to under stand other wise not may be many bt what is Transmission opacity D min D max and the latitude and or the Fog level them the Gamma any one doing even today's digital sensor can nt ignore this wonder ful presentation so nice of sir u address all as if in a class room @ 1:1 and ALL THE TIME GAMMA GRAPH ....AND THE AREA WHERE FILMS ARE STILL IN USE IS THE MEDICAL DIAGINISTIC X RAY WHICH MAY NEED TO PASS THROUGH CHEMISTRY BASED PROCESSING AND AN OTHERWISE A DRY SUB AND WHO DOES WANT TO INVOLVE HIGH SCHOOL MATH SOO I M APPRECIATING THIS WORK...HATS OFF SIR ...EVEN ENCYCLOPADEA OF PHITO GRAPHY A 2 VOL VERSION OF 1980 S NT GONE TO TBUS DEPTH AND CLEARLY THEY MENTIONED TTHAT THE IDEA BEHIND NT ELABORATIVE IS NT TO MAKE MANY USER TO AVOID PHOTOGRAPHY AND THE EVER LATEST OF THE RECENCY RE PUBISHED THE FOCAL ENCYO PADEA EVEN NT POWER FUL TO ITS JST PRVS 2 VOL VERSION...SO ONLY FEW AUTHOR HAVE WROTE THIS CHAPTER AND ONE SUCH IS A GERMAN PUBLICATION THAT SENSITO METRY WHEIC IS ALSO A MYTH CUTTER TOO THAT...ARE ASDOCIATED WITH PRICESS TO MANY AREAS...SO SIR THANKS AND ATLEAST NT MANY ELECTRONIC DEVICES U USED ATLEAST AS OF NOW...HOW TO RECOGNIZE UR THIS WORK I M MISSING EXACT WORDS AND REOEATING THANKS ..MANY THANKS..ARE SOO EMBARRASING WILL BE MORE FROM U IN ANTICIPATION

[@jinxinjing4823]

hard core knowledge👍👍

[@bassemi.eskander9194]

i know it's may be a stupid question but I really don't know what is step wedge made for ?

[@SilntObsvr]

This is a very good tutorial -- I've never seen this sort of basic sensitometry explained in an intelligible fashion in the fifty years I've been learning photography. That said, your chart of log millilux - density really calls for a spreadsheet. Those didn't exist when this was invented, but even your phone should be able to run a spreadsheet (AndrOpenOffice, if you're on Android) that will create the chart as it does the calculations.

[@TheNakedPhotographer]

The day I use a spreadsheet in my photography is the day I die!

[@olafwDE]

Good idea to collect the data on a mobile device, it just needs some thinking ahead if one wants to benefit from the zone scale on the x-axis as well.

[@SilntObsvr]

@@TheNakedPhotographer Good grief, it's not like I asked you to shoot digital! I'm older than you (unless you're a lot older than you look), and when I see a bunch of data on two axes like you collected in this video, my first thought is to put it into a spreadsheet, and let the sheet create the graph. Then again, I first used Lotus 1-2-3 on a DOS machine in 1987.

[@TheNakedPhotographer]

I’m 42, but I don’t use spreadsheets.

[@stealthvanlife6867]

@@TheNakedPhotographer After reading this and other related comments, I like you even more.

[@chuck4x5]

This is great

[@jakobstyrupbrodersen926]

Excellent demo, thanks a lot :-) And thank you so much for yet again exposing your self ;-) I have heard about this method before, but never quite understood it. Until I watch your fine demo :-) And I'm seriously considering it since it is not dependent on constant outdoore light conditions, either clear blue sky or stabile overcast. I discovered sensitometry 2 years ago and it greatly improved my negatives and final prints. I use the Ansel Adams method shooting a white card board outdoor exposing for all 11 zones (0-10 in the zone system). But with the Danish costal climate with constantly drifting clouds this approach requires a lot of patience and results in less work done. Question: Will the two methods give the same resulting film curve and corrected film speed EI? Thanks in advance! Best, Jakob

[@TheNakedPhotographer]

Adams’ method is part of the Zone System and will give you film information useful for that method, but it is not the same as what I demonstrated. The Zone System will take your light meter and lens into account to personalize the film speed, what I show will only deal with the film and development. It is more similar to what film manufacturers do to determine film speeds and correct development times.

[@jakobstyrupbrodersen926]

@@TheNakedPhotographer Thanks a lot for your quick answer :-) I'll stick to personalizing the film speed taking film, developer AND light meter AND lens into account. And hoping for stable weather :-) The same principles apply for reading the film curve regardless of method, right?

[@vedranr.glavina7667]

Hi is the logH a reference the same as LogH Ref from Kodak Technical Data Sheet?

[@stealthvanlife6867]

Hi, I watched your video again today and I took very detailed notes to document the steps so I can try this in my darkroom today. How did you arrive at the .9 second exposure time? That isn't clear to me and I want to make sure I know the "why" so I can adapt to my environment. I understand you wanted to keep the exposure less than 1s because of reciprocity, but I am not clear on how you arrived at the .9 second exposure time. Later in the video you shared how you decided to select one of the exposed and developed film step wedges (f2.8 vs. F4, vs. F5.6, etc) over the others, but I wasn't able to fully understand your rationale. Can you fill in the blanks for me so I can try this at home too? Much appreciated and I know how much work you are putting into this series.

[@TheNakedPhotographer]

The time was arbitrary, you can use whatever time you want. I needed to use a time close to one second without going longer because my lens aperture was already wide open. I made bracketed exposures by closing the aperture a 1/2 stop per exposure. I chose the exposure that gave me the fewest clear patches with at least one clear patch

[@laurentgauthier2029]

@@TheNakedPhotographer Hi, thank you for this very instructive video. It"s been a long time now, but I don't undertstand why to bracket exposure. I am using sheet film, do I need to exposure 2,3 or more sheet ?

[@Taj3d]

Is there an advantage in doing the exposure in a darkroom as opposed to in-camera outdoors?

[@TheNakedPhotographer]

It depends on your purpose. If you want to include your camera as part of a complete system like the Zone stuff, that works fine. This method shown here is for film characteristic only, and requires calculating your exposure in millilux-seconds, which may be difficult in camera.

[@david4god78]

Have you tried Paul Wainwrights version of placing a 4x5 step wedge with a 4x5 sheet of b+w film in a holder and photographing a white card on zone 10. then looking and judging the exposed film for seperation between the zones?

[@TheNakedPhotographer]

No, but that is essentially the same thing here, just using the camera lens as the light source instead of the enlarger.

[@stealthvanlife6867]

Hi, excellent series. Any particular mode being used on your densitometer to read the density values of your step wedge?

[@TheNakedPhotographer]

Transmission mode and visual rather than color.

[@stealthvanlife6867]

@@TheNakedPhotographer Thank you. Keep up the excellent work. Much appreciated and refreshing to see new content on analog film and the darkroom. Keep going!

[@stephendeakin2714]

Have you any thoughts on base board reflection. Does a white baseboard reflect scattered light back into the print, do yellow baseboards react with multigrade filters, does a black baseboard give a sharper print. I've no idea how to go about proving one way or another which is better or worse.

[@TheNakedPhotographer]

None of those are concerns. Stray light leaking from the enlarger head and bouncing off white walls are more important to control.

[@stephendeakin2714]

@@TheNakedPhotographer That's reassuring, I will carry on with my white baseboard. Thanks.

[@shuailuo8637]

Great video! I have a question there, why use the log E minus the density of strip? I don’t quite understand the subduction between two different units if I have understood correctly.

[@TheNakedPhotographer]

That is to calculate the exposure of the film for each section of the step wedge. Since each step of the wedge increases in density, it decreases the light passing through it to the film, so the exposure is less for each step.

[@shuailuo8637]

@@TheNakedPhotographer thx！

[@shuailuo8637]

@@TheNakedPhotographer Is that also means the Log 10 (2340) millilux-second is the theoretical density which was projected by the enlarger?

[@Ivan-gh1wm]

@@shuailuo8637 The film density is not equal to its exposure. Let's say given the same illuminance and time interval, density of 200 ISO film = density of 100 ISO film + 0.3

[@Arturo.H.M]

Do you know if Is possible to buy Steep Tablet today? I’m pretty sure that Kodak no longer has it, but may be some one else..

[@TheNakedPhotographer]

Stouffer makes them: stouffer.net/TransPage.htm

[@alasdairdougall7868]

To add to the sense of adventure, should be not have “39 Steps” wedge?

[@TheNakedPhotographer]

Only if you want to suffer.

[@stealthvanlife6867]

For those of us that don't have a lux meter like you and need to convert EV to lux, how do you suggest handling the EV to lux conversion formula (lux = (2 ^ ev) * 2.5) for different speed films that you want to test? The reason I ask is the conversion formula is based on ISO 100, and I assume you would need to modify the formula based on ISO of the film being tested? Any input/guidance is appreciated because I can't afford a lux meter and would like to follow your process here.

[@TheNakedPhotographer]

Figure it for ISO 100, then close the lens aperture two stops for 400, open it one stop for 50, etc.

[@stealthvanlife6867]

@@TheNakedPhotographer Excellent, thank you! That makes it easier.

[@stealthvanlife6867]

@@TheNakedPhotographer Do you think a cheaper lux meter like this one is good enough for doing the tests you showed in this video? www.amazon.com/URCERI-Illuminance-Handheld-Temperature-Measurer/dp/B075DC6X25/

[@TheNakedPhotographer]

At that price it is worth trying. You can always return it for a refund

[@stealthvanlife6867]

@@TheNakedPhotographer I will give it a try and loop back and let you know how it went.

[@pollux4447]

0:43 what happened?????

[@TheNakedPhotographer]

Nothing out of the ordinary

[@leajaffredo]

Coming from a lost French student in photography : thank you 🥹

[@flyboy61699]

Really interesting video, but this would have been so much easier in a program like Excel instead of doing it all on paper xD

[@TheNakedPhotographer]

If you can’t do it without a computer, you’re not learning how to do it.

[@flyboy61699]

@@TheNakedPhotographer Says the one using a calculator on your phone instead of a slide rule, haha! I mean, I could draw a graph by hand, but it's a perfectionism thing for me, knowing that all the points are just slightly off. But seriously, this kind of analysis would take half the time in a spreadsheet, and I would argue may be easier to learn with since the data is interactive, and you don't have to spend as much brain power on the menial in-betweens. It is 2020 after all; we might as well take advantage of that.

[@TheNakedPhotographer]

You do it any way you want, but I will not use spreadsheets to make a video.

[@dorothykloss5303]

@TheNakedPhotographer that's what they taught us in programming and in accounting classes. Learn DOS first, then move on. Do it on paper first. Great information btw. and so sorry about your mother-in-law. That's tough. I'm looking forward to using my new lux meter. I had another question about the density of the 80A filter and whether it is the same as the blue filter density in the enlarger. How would you measure that?

[@PiratePhD]

Would probably be faster to do the calculations in Excel.

[@TheNakedPhotographer]

Are you guys getting together on some web chat to find a way to make my eye twitch?

[@LaViejaConsolada]

I do not understand what's going on with you guys: you got the info, if you like to use an excel sheet, go for it. He's using a chart paper, and in a very clear way. Just thank him for sharing his knowledge.

[@isaacmuch9074]

excellent instructional videos...nakedness not a mature addition to otherwise intelligent discourse