Camera's built-in spotmeter as densitometer?
Phil Glaser
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.
Nicholas O. Lindan
> 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.
--
Nicholas O. Lindan, Cleveland, Ohio noli...@ix.netcom.com
Consulting Engineer: Electronics; Informatics; Photonics.
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/
f/256
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
Dan Quinn
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
Jtown2354
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 Glaser
> > 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
f/256
"Phil Glaser" <gla...@sustainsoft.com> wrote in message
news:a3f95acc.04031...@posting.google.com...
>
> 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.
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
Jorge Omar
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
gla...@sustainsoft.com (Phil Glaser) wrote in
news:a3f95acc.04031...@posting.google.com:
Dan Quinn
> > 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),
> 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.,
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
Dan Quinn
>
> 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.
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
Claudio Bonavolta
news:20040311190935...@mb-m04.aol.com...
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
Dan Quinn
> 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.
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
Jorge Omar
only enlarging meter.
Jorge
dan.c...@att.net (Dan Quinn) wrote in
news:b379902d.04031...@posting.google.com:
Phil Glaser
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
Jorge Omar
emailed it to the address below.
Jorge
gla...@sustainsoft.com (Phil Glaser) wrote in
news:a3f95acc.04031...@posting.google.com:
> Jorge Omar <jorg...@ieg.com.br> wrote in message
Phil Glaser
> RE: gla...@sustainsoft.com (Phil Glaser) wrote
>
> > > The Ilford EM-10 plus a step wedge for calibration.
> > > I think it might work. Dan
> >
> 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
Jorge Omar
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
gla...@sustainsoft.com (Phil Glaser) wrote in
news:a3f95acc.04031...@posting.google.com:
> Ok, I get the basic concept. Make the EM10 go green on a given test
Dan Quinn
> > > > 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
> 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
Phil Glaser
> 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
Jan T
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
"Dan Quinn" <dan.c...@att.net> schreef in bericht
news:b379902d.04031...@posting.google.com...
Claudio Bonavolta
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,
--
Claudio Bonavolta
http://www.bonavolta.ch
Phil Glaser
> 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
Jtown2354
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.
Dan Quinn
> 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
> > > > >
> > > > 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. P. Glaser