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Thread: DIY UV light meter for alternative photographic processes

  1. #1

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    Mar 2015
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    DIY UV light meter for alternative photographic processes

    I practice a number of alternative process kallitype, pt / pd, saline and albumen paper, cyano, collodion ... I have a well equipped lab or things are clear, I know my exposure time with my insoleuse UV and my protocols even if it evolves are validated. But I wanted to make large prints and my insoler is limited to 40x50cm, I have more room to make a larger and sometimes I want to make demos out of the lab and suddenly it's complicated. In addition to the arrival of good weather I wanted to leave the lab and see if there was a difference in rendering between artificial UV and natural light, the problem is that the expo time with non-POP processes are quite difficult to evaluate, I practice a lot of kallitype with Gold or Pt / Pd toning and the eye, even if the expo is good or not, it is mission impossible. I wanted to find outside the opportunity to control the exposure for these processes and not lose my calibration work in the lab.

    It was therefore necessary that I could recover the good process exposure value of my insoleuse in the lab and apply it outside or the conditions are very variable depending on the day, but also during the expo time, a cloud that pass and it changes the deal. So I created this device a kind of UV light meter to meet my needs.

    I have finalized the beta version of my UV light meter for alternative processes, it allows me to make exhibitions out of the lab in daylight, the electronic and computer part is finalized and fully functional, I'm on modeling the box to finalize this project, even if I continue the test phase and still brings some improvements.

    Regarding the overall operation, on the home screen we have the current UV unit that allows to choose a place for the printing frame, I have for the occasion defined a UV unit value (UUV). A UV Live menu allows to know the number of UUVs over a period of time, a count of hours / minutes / seconds begins and the UUV is incremented (the sampling frequency is configurable) this feature allows to know the number UUV needed for good exposure of a process, but also to expose if you stay close and wait for the UUV corresponding to your correct exposure. When you start a new process, you can simply exchange the number of UUVs with other users, it gives a good basis of work knowing that variations in chemistry and procedure can cause slight variations. If you have an insolvent and an already defined protocol, you get the number of UUVs needed for your process, chemistry and protocol.

    It is possible to configure with the menus three different processes, one defines the name of the process and the number of UUV for a correct exposure. This data is saved.

    For the exposure with countdown the function Timer UV allows to select the process, one recovers automatically UUV necessary for the good exposure which one has been configured. The beginning of the expo is started, the analysis is done in real time according to the defined sampling frequency and an evaluation of the remaining time is displayed. The measurement obviously takes in real time the UV variations. We have a PAUSE function to possibly move the printing frame (to cover during the break) to a more or less sunny area if we do not want the exhibition to continue during the trip. When the exposure is good, an audible alarm sounds. It only rained to cover the chassis and develop.

    I have also integrated a calibration feature that allows sensor calibration, definition of UUV sensitivity scale and definition of sampling frequency (UUV analysis every x milliseconds)

    I did tests with different weather conditions and printing frame moves during the expo which resulted in variations of the expo from 1 to 30, and for now all the expos are perfect.

    Here are some specificities:

    UV sensor with a sensitivity range between 280 and 390nm and a peak between 310 and 370nm
    LCD display 2 backlit lines
    5-key keyboard
    End of Expo warning buzzer
    9v battery power
    Software update via USB

    Here are some pictures of version 1 beta in action, the final version will be slightly different and more compact.
    Click image for larger version. 

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  2. #2
    bob carnie's Avatar
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    Re: DIY UV light meter for alternative photographic processes

    I want the final version when you complete, I see the need for this...

    should ask is there a current commercial unit that you are aware of??

  3. #3

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    Re: DIY UV light meter for alternative photographic processes

    Quote Originally Posted by meditant View Post

    UV sensor with a sensitivity range between 280 and 390nm and a peak between 310 and 370nm
    LCD display 2 backlit lines
    5-key keyboard
    End of Expo warning buzzer
    9v battery power
    Software update via USB

    Here are some pictures of version 1 beta in action, the final version will be slightly different and more compact.
    Nice DIY, IMHO it looks it should work like a comercial one, and at a fraction of the cost.


    Quote Originally Posted by bob carnie View Post
    should ask is there a current commercial unit that you are aware of??
    $190, new, UV250-410nm UV Integrator Radiometer UV Energy Meter Tester UV-150

    (https://www.ebay.com/itm/UV250-410nm...8AAOSwFmxaXcl0)


    I was to buy it for my first Carbon tests, but I use Luxmeter Android App for relative measurements, I place an UV pass filter for UV photography on the phone sensor. I plan to calibrate it with a Ocean Optics USB 2000 spectrometer, but this still pending.

    Smartphones usualy have a calibrated photocell in the face to adjust screen auto-brightness, Luxmeter apps uses that sensor, it is not an "scientific" instrument because it's quite directional, and of unknown spectral sensitivity, but good enough to calibrate a personal process, single problem is that is if you change smartphone you should reference the old readings to the new ones, but anotating readings from particular light source irradiation.

    Another thing is that depending on the spectral power distribution of UV light (more 395nm or more 300nm...) the effect in the alternative process may vary for the same J/cm2 irradiation. Today we have cheap 100w UV leds of 395nm, more expensive for 365nm, anyway by using an spectrally stable light source then the relative readings have to be meaningful. Note that 100w UV is a lot, owe may need to throw a lot of HID power to get 100W UV...


    Another choice that don't have the integration feature, just the instant power, that may be enough if measuring time:

    $43 AMAZON: TOPCHANCES High Precision UV Strength Tester UV

    A bare $30 luxmeter (AMAZON: Luxmeter Epsilont 2000) with a UV pass filter on it

    Search for uv pass filters: https://www.ebay.com/sch/i.html?_fro...ilter&_sacat=0


    This is the $190 integrator:

    UV250-410nm UV Integrator Radiometer UV Energy Meter Tester UV-150

    Click image for larger version. 

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    Brief introduction:

    1. The UV-Integrator is used to measure UV energy and UV does of different light sources, especially on printing machines. It is ideal to ensure quality control of printing and drying process.
    2. The UV-150 tester is a high quality UV measuring instrument. It is used to measure UV energy of different light sources, especially on printing machines. It is ideal to ensure quality control of printing and drying processes.
    3. Small size, heavy duty pass-through Integrator with a diameter of 90 mm.
    4. It is reliable and simple to use.
     

    Specification:

    Technical Data:

    Spectral range: UV 250- 410 nm
    Measuring range: 0 to 5,000 mW/cm2
    Display: 6-digit LCD
    Display range: 0 to 999,999 mJ/cm2
    Power source: long life 3.6 V Lithium Battery
    Power consumption: 100 uA
    Battery service life: 10,000 hrs
    Dimensions: Diameter(90 mm), Height (12 mm)
    Weight: approx. 5.25 ounce (150 grs.)
    Temperature range: 0 to 70 Centigrade
    Heat protection: Heat shield on back plate
    Base Accuracy: +-5 %
    While on the conveyer belt, the UV-Integrator 150 can withstand 90-100° Centigrade for up to 10 seconds

    Suitable equipment: UV UV dryer, exposure machine, conveyor belt, UV lamp, UV curing machine and other equipment, UV energy detection.

     

  4. #4
    bob carnie's Avatar
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    Re: DIY UV light meter for alternative photographic processes

    thanks Pere

  5. #5

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    Re: DIY UV light meter for alternative photographic processes

    Very nice looking. I noticed Sparkfun has a nice looking UV sensor with lots of code examples and documentation. Been meaning to make one but have been a bit busy testing alternative Carbon print sensitizers lately.

  6. #6
    Tin Can's Avatar
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    Re: DIY UV light meter for alternative photographic processes

    Here's the one I bought.

    http://www.lightmeasure.com/

  7. #7

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    Re: DIY UV light meter for alternative photographic processes

    Thanks for your return.

    I do it for me but if some people be interested a can make a mini series.

    When I finished the final version a make a presentation film.

    I have already some ideas for version 2

  8. #8

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    Re: DIY UV light meter for alternative photographic processes

    Let me suggest interesting features that would possible with a switchable filter/sensor, by replacing the filter on the sensor it would measure UV for alternative, G-B for variable contrast paper calibration, lux·second to make sensitometric film calibration, or even working on GG as spot metering like a probe meter...

    Same hardware, just some software modes and switchable filter/sensor...

  9. #9
    Eric Woodbury
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    Re: DIY UV light meter for alternative photographic processes

    I'm curious about a couple things here. My reason is I have a bunch of MetroLuxs that I'm going to sell cheap. They are the leftover stock. These are light integrating timers for coldlight sources. With a different photo-diode, MetroLux could be used for UV. We've had a few customers over the years do this. Meditant, what is your photodetector? Here's a UV photodiode that isn't too expensive. It's unfiltered, but I'm not sure that makes a difference to your process.

    https://media.digikey.com/pdf/Data%2...12-UVA-011.pdf

    The other question is what kind of glass do you use in your print frames? I've always heard that "glass" doesn't pass UV. I know you can't get sunburned in a glass greenhouse.

    Thanks,
    EW

  10. #10

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    Re: DIY UV light meter for alternative photographic processes

    Quote Originally Posted by Eric Woodbury View Post
    The other question is what kind of glass do you use in your print frames? I've always heard that "glass" doesn't pass UV. I know you can't get sunburned in a glass greenhouse.

    Thanks,
    EW
    Common window clear glass allows to pass some 75% of sunlight's UVA, but blocks UVB. UVB is responsible of skin sunburn.

    UVA (320-400 nm), UVB(290-320 nm) and UVC (200-290 nm). 96.5% of the UV in sunlight is UVA, UVC is effectively filtered out by the ozone layer. UVB is only 3.5% of total UV in sunlight.

    So common clear glass only blocks 1/4 of the UVA in an alternative process. Some window glass may have coatings blocking UV, also tinted green glass blocks a lot of UVA IIRC.

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