Camera'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 ****er!

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.

"Phil Glaser" wrote

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
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

"f/256" wrote

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

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

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

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

"Phil Glaser" wrote in message
om...

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

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

(Phil Glaser) wrote in
om:

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

(Phil Glaser) wrote


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

"Jtown2354" a écrit dans le message de
...
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