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Photo Forum / Film Photography / Darkroom / March 2004Camera's built-in spotmeter as densitometer?
Hi, I've read Phil Davis's description of using a dedicated spotmeter as a densitometer and have found various postings from this newsgroup on the topic. I don't have a dedicated spotmeter, but my Nikon F4 does have a spotmeter mode for its build-in light meter. This meter gives measurements in 1/3 EV increments, which is what would be necessary for reading negative densities. What I am contemplating is to get a reverse-mount adaptor for my 50mm F 1.4 Nikor lense and using the camera to read negative densities. Is there any reason, fundamentally, why this approach shold not work just as well as a dedicated spotmeter? My second concern involves the nature of the aparatus I would need to build in order to make this arrangement work. The project that Davis describes seems like a rather involved affair that would take me quite a few hours to put together in the woodshop. On the other hand, Les Meehan, author of "Creative Exposure Control," presents a much simpler scenario (http://www.zone2tone.co.uk/testingm.htm), where you place the negative on a light-box, mask the negative with a piece of cardboard that has a 20mm hole in it, hand-hold the light meter, focus, and take the reading. If the readings I could get using this approach with my Nikon and a reverse-mounted lense would be reasonably accurate, that would be great. I should also clarify what my accuracy needs are. I am not looking to exhaustively characterize the H&D curve of the films I'm using. All I want to do is determine my EI and proper development times for N, N-1, N+1, etc. I am only examining the Zone I and Zone VIII densities, and relative accuracy is more important to me than absolute accuracy. As an aside, I purchased a densitomter on e-bay that so was so cheap ($30) that it was worth the gamble. Well, I lost the gamble (the unit powers up but does not take readings). Notwithstanding the success stories about buying working densitomters for under $100 on e-bay, I find that the vast majority of cheap ones are sold "as is," whereas the proven working ones (most people who sell them don't know how to tell whether or not they're working) go for more than that. More significantly, I have a very small living space, and, having absorbed the fact that a densitomter is a substantial piece of equipment, I am leary of the space it would take to own a densitomer. As a second aside: I have tried every photofinisher and darkroom in my locale and no one is willing to take densitometer readings for me. The worst of it is the art school at the locall university, where you can rent darkroom time at $20 a pop, but the desnitomer is off limits to folks who aren't students or faculty. What a pisser! My last resort is to use Meehan's contact-printing method (http://www.zone2tone.co.uk/article_2.htm), but I don't like that idea both because it involves use of more materials and because I'm very much at the beginning of the learning curve, and don't know if I can trust my own judgement about whether a print tone matches an 18% grey card. Thanks for your help. > I've read Phil Davis's description of using a dedicated spotmeter as a > densitometer ... Nikon F4 ... light meter ... in 1/3 EV increments That's good enough for taking pictures but not for densitometery. You eye can resolve to 0.01 OD when the two density patches are next to each other. You eye, if given a standard for comparison, is better than any photographic lightmeter made. You will do better with a step tablet and a bit of cardboard with a hole(s) in it to isolate the patch on the tablet and test negative. Compare the known density of the step tablet to the unknown negative. You can get step tablets from Stoufer, and possibly ebay. You don't need a calibrated one, so don't waste money. http://www.stouffer.net/Stoufferhome1.htm > As an aside, I purchased a densitometer on e-bay that so was so cheap > ($30) that it was worth the gamble. Well, I lost the gamble... On ebay, as anywhere, expect to pay the average price for the average unit: an average working densitometer is in the 150-350 range. An old QA model as used by mini-labs in the 80's, such as a Noritsu, is usually a good buy. When the add states "don't know what it is", "what it does", "haven't had a chance to test it", "when I plugged it in it ....", "so I guess it is OK", "a fine addition to any collection", "in great condition for its age", "rare" .... go to the next ad. If the item is priced very low, and there is no bidding war, other bidders may know why to stay away.  SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ Phil, Another alternative is to use a transmission/projection calibrated step wedges from http://www.stouffer.net then it is just a matter of, by comparison, either visually or using your Nikon's spot meter, finding the wedge that matches your test negative density. Alternatively you could do the comparison by scanning the step wedge and the negative and then use Photoshop density reading to find the wedge that matches the negative. Guillermo > Phil, > [quoted text clipped - 6 lines] > > Guillermo I think that's it! You've supplied the missing link. The Ilford EM-10 plus a step wedge for calibration. I think it might work. BTW, for $77 my Tobias TB+ came with all the extras, in near new condition, and works great. One must be patient with eBay. Dan > > Another alternative is to use a transmission/projection calibrated step > > wedges from http://www.stouffer.net then it is just a matter of, by > > comparison, either visually or using your Nikon's spot meter, finding the > > wedge that matches your test negative density. > I think that's it! You've supplied the missing link. The Ilford EM-10 > plus a step wedge for calibration. I think it might work. Um, can you elaborate? I've been able to divine that the Ilford EM-10 is an "exposure monitor" and an inexpensive one at that ($23 at B&H), but I'm not sure exactly what it does (Ilford's website is lacking in usability and I could not find this item there) and how I would use it in combination with the step tablet to read the densities of my negatives. Since it sounds like an inexepnsive solution, I'd love to hear more. > BTW, for $77 my Tobias TB+ came with all the extras, in near new > condition, and works great. One must be patient with eBay. Dan Perhaps I'll go that route eventually but for now I want to try to keep it simple with equipment. I've got limited resources, and would rather put that $77 dollars towards an MF camera. Thanks! --Phil > Um, can you elaborate? I've been able to divine that the Ilford EM-10 > is an "exposure monitor" and an inexpensive one at that ($23 at B&H), [quoted text clipped - 3 lines] > negatives. Since it sounds like an inexepnsive solution, I'd love to > hear more. You mount your test negative on the enlarger and place the EM10 on the baseboard, turn the adjustment wheel until led turns green, then remove the test negative and place the step wedges sheet and find the one that would turns the EM10 led green, the density of that wedge is the density of your test negative. You may want to make a mask so only one wedge is projected at a time. > Perhaps I'll go that route eventually but for now I want to try to > keep it simple with equipment. I've got limited resources, and would > rather put that $77 dollars towards an MF camera. You could also use your Nikon spot metering system to do it, do the same as above only instead of using an EM10, you meter the enlarger projection with your camera set to spot metering, you may even want to mount the camera on a tripod to make sure the angle of incidence doesn't change. Guillermo Take a look at this link: http://fox.vis.pl/filmy/ilford/em10graph.pdf Here you have a curve with relative density in the vertical side and dial scale in the horizontal one. I believe this curve is representative, but not 'exact' for any meter. So, by using the EM-10 to compare a step tablet to an negative, much more precise readings will be obtained. BTW, each EM-10 is (was, I belive it's out of production nowadays) hand calibrated using a 0.5 lux source. Jorge >> > Another alternative is to use a transmission/projection calibrated >> > step wedges from http://www.stouffer.net then it is just a matter [quoted text clipped - 24 lines] > > --Phil > Take a look at this link: > [quoted text clipped - 9 lines] > BTW, each EM-10 is (was, I belive it's out of production nowadays) > hand calibrated using a 0.5 lux source. The 0 to 100 values I recorded do correspond to those in the article. Two "suggest"s are mentioned. Although one may gain some idea of the contrast range of the negative the EM-10 does not indicate the exposure time or grade of paper. Is the subject of the article some other enlarging meter? Dan I can't read Polish, but looking a the homepage the EM-10 seems to be the only enlarging meter. Jorge > The 0 to 100 values I recorded do correspond to those in the article. > Two "suggest"s are mentioned. Although one may gain some idea of the > contrast range of the negative the EM-10 does not indicate the > exposure time or grade of paper. > Is the subject of the article some other enlarging meter? Dan > Take a look at this link: > > http://fox.vis.pl/filmy/ilford/em10graph.pdf When I try to access this link I get a "connection refused" error. If someone else can see this document, could you download it and send it to me by e-mail? Thanks! --Phil Phil emailed it to the address below. Jorge >> Take a look at this link: >> [quoted text clipped - 7 lines] > > --Phil > > The Ilford EM-10 > > plus a step wedge for calibration. I think it might work. Dan > Um, can you elaborate? I've been able to divine that the Ilford EM-10 > is an "exposure monitor" and an inexpensive one at that ($23 at B&H), [quoted text clipped - 3 lines] > negatives. Since it sounds like an inexepnsive solution, I'd love to > hear more., I've the EM-10 off the shelf and a step wedge in the enlarger. I'll play with it some this evening and let you know. The EM-10 is a light meter approximately .75 h x 2 w x 6 l inches. It sits on the easel or baseboard. It has an off/on and a dial calibrated from 0 to 100. Dan RE: glaserp@sustainsoft.com (Phil Glaser) wrote > > The Ilford EM-10 plus a step wedge for calibration. > > I think it might work. Dan [quoted text clipped - 6 lines] > negatives. Since it sounds like an inexepnsive solution, I'd love to > hear more. Test conditions: Full frame projection of a 21/4 square 21 step step wedge; Projection width 41/2 inches; Step one through eleven measured; Lens, 105mm 5.6 Nikor at f22. These values were recorded for step one through eleven: From the 0 to 100 dial: 14, 18, 22, 25, 32, 44, 55, 70, 76, 83, and 91 As you can see the response of the EM-10 is not linear. Your film to be tested should replace the step wedge in the carrier. Interpolating should allow for 1/4 or better stop resolution. Use a 31 step step wedge to do even better. One tip, stop down further for a greater seperation of values with the lower steps. BTW the EM-10 has on it's nose a very small light sensor. In effect it is a small angle spot meter. If I left anything out let me know. Dan > RE: glaserp@sustainsoft.com (Phil Glaser) wrote > [quoted text clipped - 4 lines] > Interpolating should allow for 1/4 or better stop resolution. Use a 31 > step step wedge to do even better. Ok, I get the basic concept. Make the EM10 go green on a given test negative, and then find the step-tablet wedge that also causes it to go green, and there's the density. Simple. My only concern with this approach is this: what if one of the wedges does not exactly match the density of the negative. I have the stouffer T2115 21-step tablet that has the specifications listed on this page: http://www.stouffer.net/T2115spec.htm. The densities are .05, .20, .35, .50, etc. My understanding is that, for example, the Zone I negative should be 1/3 stop (i.e., .10) denser than base+fog. So suppose base+fog is neither .05, nor .20, but somewhere in-between. It seems unlikely to me that the step wedge is going to be right on the button with one of these values. What do I do then? Are those numbers on the dial meaningful in that case (what do they mean, anyway). Is that what you mean when you say that "Interpolating should allow for 1/4 or better stop resolutioon." Can you elaborate on what you mean? How would I interpolate? Finally, it was suggested in another post that I could use my Nikon's spot meter for the same purpose. I gather then that while the in-camera spotmeter is not good enough to read densities off of a negative on a light table, it would be adequate for the strong enlarger light? I appreciate everyone's help with this. I finally feel that I'm getting closer to an affordable and simple way of calibrating my process. Thanks! --Phil Phil If you use the chart I've sent you, by turning slightly the knob and looking at the chart, you will know how much is the difference (keep the knob for readings between 70 and 90 where it's more linear). Jorge > Ok, I get the basic concept. Make the EM10 go green on a given test > negative, and then find the step-tablet wedge that also causes it to [quoted text clipped - 28 lines] > > --Phil glaserp@sustainsoft.com (Phil Glaser) wrote > > > > The Ilford EM-10 plus a step wedge for calibration. > > > > I think it might work. Dan > > > > > Your film to be tested should replace the step wedge in the carrier. > > Interpolating should allow for 1/4 or better stop resolution. Use a 31 > > step step wedge to do even better. Dan > Ok, I get the basic concept. Make the EM10 go green on a given test > negative, and then find the step-tablet wedge that also causes it to > go green, and there's the density. Simple. > > My only concern with this approach is this: what if one of the wedges > does not exactly match the density of the negative. The first step is to calibrate YOUR EM-10 using your step wedge. Steps one through eleven should be enough. Now you have the values from the 0 to 100 dial. The second step is to read your test negative values. All conditions must be the same as when calibrating. Lets say one of your readings is 29. From YOUR table of values you find it lies at a midpoint between two step values. Read that as 1/4 step above the lower of the two step values. The EM-10 will only get you into the ballpark. I may even find it handy myself. The sensor amounts to perhaps less than a one degree spot meter. I've several rolls of exposure/developer test film and may see how closely it agrees with my densitometer. As for using a camera I could'nt say. I'd think it not very handy to use. Dan Maybe I'm missing some point here, but until now I didn't read anything about the density of the filmbase + fog. AFAIK the density of a negative is measured _above_ fb+f. What if your negative does not compare to the step tablet in this matter...? Jan > > > > > The Ilford EM-10 plus a step wedge for calibration. > > > > > I think it might work. Dan [quoted text clipped - 24 lines] > As for using a camera I could'nt say. I'd think it not very > handy to use. Dan > Maybe I'm missing some point here, but until now I didn't read anything > about the density of the filmbase + fog. AFAIK the density of a negative is > measured _above_ fb+f. What if your negative does not compare to the step > tablet in this matter...? The fb+f is measured on a clear, unexposed area of the film. It is step one of the step tablet or wedge. IIRC Mr. P. Glaser has plans to make film exposure/devlopment tests. My step wedge has a .06 for step one when measured with my densitometer. He should establish a clear area density then subtract that value to find the density range. His step wedge values are the EM-10's 0 to 100 dial values. When he calibrates his EM-10 with his step wedge he establishes the relation- ship. The 0 to 100 dial is no more than a gain control. So, in a word, subtract. Dan > > > > > > The Ilford EM-10 plus a step wedge for calibration. > > > > > > I think it might work. Dan [quoted text clipped - 24 lines] > > As for using a camera I could'nt say. I'd think it not very > > handy to use. Dan Phil (Glaserp) and Claudio - frankly, a computer is not needed to use a darkroom exposure analyzer as a densitometer. A simple calculator will do the job very nicely - as one is simply using log functions and dividing. In the event that someone questions the accuracy of using an analyzer as a densitometer - I found that my analyzer was within one-third of a stop when used on a certified Kodak test strip. The analyzer was much more accurate that either of two commercial densitometers - however, I cannot confirm the capabilities and knowledge of the two densitometer operators (commercial photographer and a small college). Yes, I use a computer program for adjusting color filtration packs and exposure times, et.al. This and other programs are those written by myself and are executable files that will work in DOS, windows or LINUX. And like others, I have no respect for windows - though I still have it on one computer. Phil - yet another possibility - should you have a good darkroom exposure analyzer, it can be used as a densitometer. I use a Beseler PM3L (digital color analyzer) and have developed a procedure to use it as a densitometer. Should you be interested, let ma know via e-mail. ---- Jerry/Idaho > Phil - yet another possibility - should you have a good darkroom exposure > analyzer, it can be used as a densitometer. I use a Beseler PM3L (digital > color analyzer) and have developed a procedure to use it as a densitometer. > Should you be interested, let ma know via e-mail. ---- Jerry/Idaho You're right, a darkroom exposure meter may be used as a transmission densitometer and for several other uses (contrast evaluation, ...). I developped a software that groups such functions: http://www.bonavolta.ch/hobby/en/photo/labsoft.htm Regards, Claudio Bonavolta http://www.bonavolta.ch > You're right, a darkroom exposure meter may be used as a transmission > densitometer and for several other uses (contrast evaluation, ...). > I developped a software that groups such functions: > http://www.bonavolta.ch/hobby/en/photo/labsoft.htm Hi Claudio, I am intrigued by your software. I've looked over your website and it sounds great. The problem for me is I don't use Windows. Ever since Microsoft came out with it's scheme for charging more money per hardware upgrades with XP, and since the major software and hardware manufacturers are colluding to undermine our digital freedom (e.g., "trusted computing"), I have, for my home system, sworn off Windows and am using Linux instead. I couldn't find where your site describes the language and development environment for your application. I'm wondering how easily it could be ported to Linux and/or whether you would feel comfortable releasing the source code under GNU (or something similar) so that it might be ported to Linux? --Phil > > You're right, a darkroom exposure meter may be used as a transmission > > densitometer and for several other uses (contrast evaluation, ...). [quoted text clipped - 16 lines] > > --Phil Hi Phil, This software is developed using Borland Delphi. A linux version should come sooner or later as Borland has a "Delphi-for-Linux" named Kylix which is pretty compatible with Delphi. Porting the software shouldn't be very difficult, I should have only few components/code that do not have its Linux counterpart and should be rewritten diferently. But, before this I have three things to do: - finish the software as version 3 is currently in progress (it adds hardware to control the enlarger and a RGB light sensor). This software is mainly developed for my own needs, sharing it with others is just a personal pleasure. - make a commercial product for the photographers that are not brilliant with the soldering iron :-) This includes the hardware, software will remain free. - learn the basics of Linux ... I hope to finalize version 3 by this summer and the commercial product by the end of the year. So, why not a Linux version in 2005 ? I'm absolutely not a Bill Gates' fan ... Don't ask me to publish the sources as it would be to easy to include it in a competitor software. I feel comfortable in sharing the software for free but I wouldn't appreciate someone else make profit with it (I already give to much informations on my website !). I need time to think about it, thanks for your comments, SignatureClaudio Bonavolta http://www.bonavolta.ch > This software is developed using Borland Delphi. > > A linux version should come sooner or later as Borland has a > "Delphi-for-Linux" named Kylix which is pretty compatible with Delphi. I develop in BCB so I'm quite familiar with the VCL and the Delphi/Kylix world. Sounds like a great plan. I look forward to a linux version. > Don't ask me to publish the sources as it would be to easy to include it in > a competitor software. > I feel comfortable in sharing the software for free but I wouldn't > appreciate someone else make profit with it (I already give to much > informations on my website !). I totally respect your concern. The one thing to consider is that the GNU license is designed to prevent the type of situation you'r concerned about, insofar as it forces anyone who reuses your code to publish the source along with it and to include your copywrite. Whether you publish the source or not you've done a great service for the traditional darkroom community and I look forward to using the software. Thanks! --Phil |
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