Re: Sensitometer For B&W Film?
Quote:
Originally Posted by
Greg Davis
You guys should read his original post again. He is not looking for a densitometer to read film density. He is looking for a sensitometer to expose film density. Completely different machine and purpose.
Does he produce black and white films and does he have to measure any densities daily to ensure a consistent production?
That is rather unlikely, IMHO. That's why I assumed that he meant a densitometer rather than a sensitometer. Sorry.
Furthermore, the term "sensitometer" contains the word "meter", which refers to an activity of "measuring". I don't see that exposing grayscales on a piece of film involves "measuring".
But: if you buy a sensitometer (sensitoexposer), just send me some normally exposed gray scales on my favorite film ... You could provide us all with it.
Re: Sensitometer For B&W Film?
Good video Greg
Quote:
Originally Posted by
Greg Davis
You guys should read his original post again. He is not looking for a densitometer to read film density. He is looking for a sensitometer to expose film density. Completely different machine and purpose.
I use a Tobias Wejex I-W that uses a small incandescent bulb with nd and 80A filters to convert it to daylight. About a 1/2 second exposure time. There is one on eBay right now for $200, but you just missed one for $5. I show mine in this video:
https://youtu.be/VNbyShwYi6c
Re: Sensitometer For B&W Film?
That is a great Wejex, thank you for showing the insides, now I want one. I have a small collection of sensitometers including the older "Black Box" Wejex, but I don't have that one. I'll have to keep my eyes open for one.
Re: Sensitometer For B&W Film?
Quote:
Originally Posted by
Daniel Casper Lohenstein
Does he produce black and white films and does he have to measure any densities daily to ensure a consistent production?
That is rather unlikely, IMHO. That's why I assumed that he meant a densitometer rather than a sensitometer. Sorry.
Furthermore, the term "sensitometer" contains the word "meter", which refers to an activity of "measuring". I don't see that exposing grayscales on a piece of film involves "measuring".
But: if you buy a sensitometer (sensitoexposer), just send me some normally exposed gray scales on my favorite film ... You could provide us all with it.
To use the sensitometer a calibrated step wedge is paced in contact with the film. Yes, without that part, the machine is useless.
Re: Sensitometer For B&W Film?
Quote:
Originally Posted by
ic-racer
To use the sensitometer a calibrated step wedge is paced in contact with the film. Yes, without that part, the machine is useless.
I've been thinking. I'm not a native English speaker. Everything takes a little longer with me.
in the german large format forum a user has the idea to use a contact copy box with a flash. so he can control the iso, by power.
he uses darkslides with holes to expose the stouffer card. so he has 3 different iso per step.
i myself would like to use the enlarger for the contact copy. that should be enough. but with which exposure time?
Re: Sensitometer For B&W Film?
Quote:
Originally Posted by
Daniel Casper Lohenstein
I've been thinking. I'm not a native English speaker. Everything takes a little longer with me.
in the german large format forum a user has the idea to use a contact copy box with a flash. so he can control the iso, by power.
he uses darkslides with holes to expose the stouffer card. so he has 3 different iso per step.
i myself would like to use the enlarger for the contact copy. that should be enough. but with which exposure time?
Enlarger exposure time can be problematic because many enlarger timers don't go below 1 second. Making a sensitometer is not that hard, but make very sure of two things. 1) The field on which the step wedge is placed is PERFECTLY EVENLY illuminated and 2) The level of illumination will not change from year to year, month to month or day to day.
Re: Sensitometer For B&W Film?
Quote:
Originally Posted by
Greg Davis
You guys should read his original post again. He is not looking for a densitometer to read film density. He is looking for a sensitometer to expose film density. Completely different machine and purpose.
I use a Tobias Wejex I-W that uses a small incandescent bulb with nd and 80A filters to convert it to daylight. About a 1/2 second exposure time. There is one on eBay right now for $200, but you just missed one for $5. I show mine in this video:
https://youtu.be/VNbyShwYi6c
+100!
I just wrote about it yesterday ... https://www.largeformatphotography.i...=1#post1536887
If the topic author is interested (DIY), I can give more detailed descriptions of the device and place the sketch and photos.
Re: Sensitometer For B&W Film?
Phil Davis in his book "Beyond the Zone System" 4th Ed describes adapting a Pentax Spotmeter to use as a densitometer. It is a good read on film testing.
Re: Sensitometer For B&W Film?
Use a colour analyzer like the Beseler PM2a, which can read black and white negatives and colour negatives and slides (back in the days of Cibachrome, etc) and allow you to use your colour head instead of contrast filters.
It's dead simple, and if you are doing critical b&w shots, (are no they all) shoot a good grey card with your first frames and maybe again when lighting conditions swing in extremes, with whatever filter you're using, in place.
Using a colour analyzer like the PM2a can put you within a second or three of your correct enlarger settings.
I have also used simple light meters, such as the Minolta III flash unit, with a darkroom metering attachment, the grey body, Gossen Luna Pro SBC (U.S. version) and the Gossen Luna Pro F, both with the same Gossen darkroom enlarger attachment and they both work fine.
For B&W printmaking, pretty much any good, low light, ambient meter should do the trick, so long as you are using a relatively small meter aperture for reading the negative, which allows you to read from different areas of the image.
And, yes, having a digital timer, does make a difference in fine tuning enlarger time, however, you can always slide a fractional ND filter into the filter drawer or above the negative, as needed.
IMO.
Good luck.
Re: Sensitometer For B&W Film?
Great video Greg!
Daniel, an enlarger will work fine and Greg's right. You want about a half second exposure. (Avoids reciprocity failure issues). How much light? Don't overthink. Just do trial and error. You need one step under 0.10 density to check film speed. Give more or less exposure until developed test has 19, 20 or 21 steps (of a 21 step Stouffer scale) to measure.
ic-racer's "sensitometer shootout" was an eye-opener for me. Any sensitometer will help you develop film for consistent contrast.