Programs for Photographer Tools

In this article, I will introduce the use of different programs
that can be used with the Photographer Tools.



UPLOAD SKIN PROGRAM:
The first program allows you to transfer skins directly with USB or Bluetooth in the Photographer Tools.
The Skins are custom GUIs.
To create a skin, I included in the ZIP file of the Photographer Tools (see download on this website),
a file named "Customize windows.pdf."
This program is called "Upload Skin" (Photo01).
To use this program, connect a USB cable between the computer and the "Photographer Tools",
if you wish to transfer a new Skin or edit a Skin by USB.
I strongly advise you to transfer skins with USB, USB is much faster than Bluetooth. By default, Photographer Tools,
does not activate USB and Bluetooth.
To enable USB and Bluetooth, you must go to the menu "Configuration" on the "Photographer Tools" and
press the option: "Enable BT / USB".
You can now launch the "upload Skin" program (Photographer Tools connect to the computer with a USB cable).
By clicking on the button "Download complete skin", the program asks you to select a directory
containing all the component files of a new Skin. The download takes about 10 to 12 minutes.
It is possible that testing your new skin, and you realize you've made a mistake in the coordinates of a field
or a touch area. In this case, it is possible to edit the file that contains error,
and then only transfer this file with the button "Download one file".
This program is very useful and avoids opening the Photographer Tools to access to the SD card,
if you want to create your own skins.
Photo02, an image of the "Upload Skins" during file transfer.
The "Upload Skins" is included in the ZIP file of the Photographer Tools.
To use this program, you must update the firmware of the Photographer Tools in version 1.02 (04/2013) minimum.
The update micro code (firmware) is used with the "Download Program in Arduino DUE.exe", by connecting the
Photographer Tools to a computer with a USB cable.




CALIBRATION PROGRAM:
The second very important program "Calibration.exe" is used to calibrate the light meter (exposure meter) and calibrate the colorimeter.
The calibration of the light meter and colorimeter is important in order to make measurements accurate enough for adjust
the white balance in manual mode, or to know the exposure of the shot.
I had already included in the ZIP file of the "Photographer Tools", the first version of the program "Calibration.exe".
But this version does not give a good result and it was necessary to use accurate light sources for the calibration
(an incandescent bulb of 60 watts, a fluorescent bulb 3000K and 6500K fluorescent bulb).
This new version of the calibration program offers much more flexibility in the choice of sources light.
Before you start to explain how to use the calibration program, you must understand why we need to calibrate the colorimeter and
the exposure meter. The Photographer Tools uses an electronic component to measure the RGB values (red / green / blue),
it is the TCS3414 of TAOS. The usage of a IR cut filter in front of the TCS3414, and the usage of a transparent plastic for protection,
modify the RGB values returned by the TSC3414, and do not match the good temperature of colors.
The Illuminance (value LUX of illumination to measure exposure) is also changed.
The calibration will allow to match the RGB values returned by the TCS3414 with the good temperature color and the good illuminance value.
To do this correspondence, we using a correlation matrix.

Before going further, I suggest an image (photo03) representing the spectrum of different light sources.
The light spectrum is the distribution of values red, green and blue.
As can be seen, incandescent bulb, halogen, fluorescent and sun, did not the same distribution of RGB values.
It is therefore difficult to make a calibration profile fits all light sources.
Our DSLR camera uses multiple calibration profiles to determine the correct white balance.
In auto white balance mode, the camera will use a complex measure to try to determine the correct color profile to use,
and then make the good temperature measurement colors.
In automatic mode, the DSLR cameras sometimes make mistakes, that's why we can choose directly the good color profile to use
(sun, cloudy, tungsten, fluorescent, shade, ...).
It is possible to make a unique profile for all light sources but it will not be accurate.
That is why I changed the firmware of the Photographer Tools in version 1.02 (version of 04/2013)
and add able to choose between several color profiles.
To create a calibration profile, you must choose three light sources: a hot source, a middle source and a cold source.
For example, to make a color profile for compact fluorescent bulbs, we use a first bulb having a color temperature of 2700K (warm),
another bulb of 3000/3500K, and last bulb of 6500K (cold).
For the sun, we'll do a calibration with a setting sun (2500/3000K), a midday sun (4500/5000K) and finally a very cloudy sky / gray (6500/7500K).

Photo04, the window of the calibration program. Description of the control buttons (circle 1), from left to right:
- Connect. Connects to Photographer Tools with USB or Bluetooth. If your computer has multiple serial ports,
the program will attempt to connect to the different ports at a speed of 9600, or 56000 baud.
It is therefore possible that there have several cycles connection attempt.
- New calibration. This button allows you to launch another window to create a new correlation equation (Photo06).
- Load calibration. This button allows you to upload files containing calibration equation of the colorimeter and the light meter.
- Save calibration. This button allows you to save different calibrations that you have created.
- Upload calibration. This button sends a calibration in the Photographer Tools.
This calibration will have the name you gave when saving (8 characters max).
Caution ! The Photographer Tools can only display 8 calibration profiles max.
- Restore the default calibration. This button allows you to restore the factory calibration TCS3414.
- Exit. As its name implies, this button will exit the calibration program.

Once connected to the Photographer Tools, RGB values (Red, Green and Blue) measured, are refresh every seconds (circle 2).

Circle 3, represents the correlation equation of the colorimeter.
This equation permit to get XYZ coordinates of the CIE XYZ color space, from RGB values.
The program calculates the XY coordinates of the CIE 1931 RGB color space, which allows to determine the temperature colors.
It's a bit complicated to explain but if you're interested, you can find all the information on the website of the
manufacturer of the TCS3414 (TAOS INC) and especially on Wikipedia.


Circle 4 represents the equation of light meter, because it must be corrected the RGB values returned by the sensor TCS3414
to obtain the correct value of illuminance.

Circle 5, indicates the value of the integration time.
This value is important in determining the correct value of the illuminance (for you it is only an indication,
it is used automatically by the program). When illumination is low, the integration time is 400 ms,
and can change up to 12 ms for illumination very strong (sun at noon in summer).

The button "CIE 1931 diagram" (circle 6) will launch the CIE 1931 chromaticity diagram 2 degrees (photo05).

The 1931 chromaticity diagram (photo05) can view the corrected value with the correlation equation (Circle 1),
and uncorrected which is directly calculated from the RGB values of the Photographer Tools (Circle 2).
In this window, you have the value of color temperature, and RGB values normalized to a computer (values 0-255)
but also a representation of the color displayed on a computer.
With the green and red dots you can see the deviation from the optimal curve of the standard CIE RGB 1931.

Photo06, is the window that allows you to create a calibration (by clicking on the button "New calibration").
This window has a lot of settings, but I'll explain how to use it.
Ideally, to make a precise calibration, you can use a colorimeter and a true thermal colorimeter and a luxmeter.
I do not think you have a photo colorimeter (me neither), we will use our camera and its histogram.
To determine the illuminance, the ideal is to have a luxmeter (10 - 12 Euros on Ebay from China) but you
can also use your DSLR camera for this (much less accurate method with an error of +/- 1/3EV or 20%).

Circle 1 represents the RGB values returned by the Photographer Tools.

Circle 2 is the equation, or tristimulus matrix, which will be used to create the correlation equation.
It must seem complicated, but it is not very hard to understand. To make a correlation equation,
we must have a reference, and compare it with the RGB values read by the sensor TCS3414.
This reference is the tristimulus matrix.

If you have a true colorimeter, to calibrate, simply refer directly to the values read by the thermo colorimeter,
and write it in this matrix.
If you do not have a colorimeter, do not touch the parameters of this equation.
If you change these settings, the CCT1, CCT2 and CCT3 are automatically disabled.
To enable CCT1 values, CCT2 and CCT3, simply click on the button "CIE 1931 CTC matrix".
This matrix is our reference, it is the default standard of CIE 1931 2°.
If you change the values or CCT1 CCT2 or CCT3 (circle 3), the tristimulus matrix is automatically recalculated.

Circles 4 and 5 represent the fields that define the lighting either with the parameters of your DSLR camera,
either directly with a light meter (luxmeter).

The button "Get Tools values" (Circle 6), allows you to capture RGB values returned by the Photographer Tools.

The buttons at the bottom (Circle 7), can load and save all calibration parameters.

Now that we've seen the theory (simplified), let's go to create a calibration.

The first thing to do is to choose three light sources (one hot, one intermediate and one cold).
As an example, we'll take a bulb of 40 watts incandescent (or halogen spotlight 50 Watts), another
compact fluorescent bulb of 3000K, and the last one compact fluorescent light bulb of 6500K
(6500K bulbs are used in photography, are Daylight bulbs).
Place the first bulb at about 1-2 meters from a white sheet.
I used white paper printer. Wait 5 minutes for the bulb heats up, and its color temperature stabilizes.
To be sure you have a good white and without transparency effect, use a block of ten white sheets of paper.
As you do not have thermo colorimeter, we will use the histogram of the DSLR camera to determine the value of the
color temperature of the lamp. Set the white balance of your camera in manual mode.
Place the DSLR camera in front of white block in the same axis as the bulb (see the photo07).
Take a picture and look at the histogram. Change the temperature value on your camera,
until the red, green and blue histogram are perfectly aligned.
Pput the value of color temperature recorded on the camera in the field CCT1.
If you have a light meter, measure the Lux value by placing the light meter in front of the white paper and put
this value in the Lux field (circle 5).
If you do not have a luxmeter, simply take a photo and note the values of aperture, ISO and speed.
Report these values in the corresponding fields (circle 4).
Now we will see the RGB values read by the Photographer Tools.
Place the Photographer Tools in front of the block of white paper, in the axis of the bulb.
Click on the button "Tools Get values", values read by the Photographer Tools are writed directly in RGB fields "Measured Values".
Now that we are done with the first bulb (Hot Color column), you must repeat the same technique with the
bulb 3000K (Middle column color: CCT2 ...), and finally with the bulb 6500K (Cold Column color: CCT3, ...).
It remains to click on "Create new correlation matrix and quit" to generate the correlation equation.
Before, you can click on "Save config" to save all the parameters of this calibration.
This can be useful to save the settings, to refine the calibration if you wish.

By default, as we have do a measure of color temperature bulbs with RGB histogram perfectly aligned,
we will have the true color temperature.
That will always provide a photo with white really white.
If you want to set up calibration profiles closer to human vision, it is sufficient simply to increase the field CCT1 values
and CCT2 (not CCT3 because 6500K corresponds to a true white).
Example: If you measured 2780K with bulb of 40 watt incandescent, put 2900 or 3030K.
For compact fluorescent bulb 3000K, can be set for example to 3230, and after generate a new correlation matrix.
Caution ! The compact fluorescent bulbs tend to have a pretty green colorimetry, so even if you have the true
value of color temperature, it is possible that the picture is green.
If you are in this case, correct color through the menus of your DSLR camera
(see the documentation for your DSLR to provide fine correction of the white balance).
I found (for example with a compact fluorescent light bulb 4000K), it was necessary to put two notches down to offset the green.
The processor of our camera made this micro correction in the green alone (if it is not mistaken of course).

In the ZIP file of the Photographer Tools, I enclose an excel document with different values,
than I used to make calibration profiles.

To change the calibration profile in the Photographer Tools:
- Set Photographer Tools on the window "Exposure and WB"
- Press the "WB" field which displays the color temperature.
A menu appears with a list of color profiles uploaded on the Photographer Tools.
Simply press on the profile you want to use.

FLASH CALIBRATION PROGRAM:
This new program allows you to easily calibrate the flash meter of the Photographer Tools.
This flash meter is fairly accurate. After calibration, I have no measurement error for different illuminances of flash.
The error rate is less than 1/3 EV.
The flash meter allow to measure aperture between F1 and F51 (for ISO 200).
The measuring range in 8 EV to 19 EV.

Why calibrate the flash meter?
Electronic components all have a tolerance, and their value is not accurate.
So it can tweak the exposure measurement, calibration is required.
You can also add a hemispherical diffuser on the flash meter, it will be necessary to make a calibration.
By default, I have not put hemispherical diffuser, but if you want, you can put one,
as a Lumidisk or Lumisphere Sekonic.

To calibrate the flash meter, you must do three measure with three steps of flash power.
for example, measure with 1/2 of the power, and another measure than 1/8,
and finally a last measure to 1/32 the power of the flash.
Some flash (flash studio for example) is a power setting from 1/1 to 1/8. In this case, measure within 1/1,
then a measurement of 1/4, and finally a measuring 1/8.

In the program I have included an easy method to determine the theoretical aperture (photo08, circle 1).
Simply indicate the Guide Number of your flash (NG is given in the manual flash depending on the position
the head of the flash or zoom), the power of flash you have set, and then the distance between the flash
and the Photographer Tools (distance in meters). Example: 1.1 for 110 cms or 2.41 for 241 cms.
Then to calculate the theoretical aperture, click on the "Calc Aperture" button.
This method is not accurate because the NG value given by the manufacturer is not very precise (variation of 1 EV).

I advise you to determine the aperture, to be use as the baseline (photo08, circle 2)
- Either use a flash meter calibrated correctly.
- Either use the histogram on your camera.

To determine the correct exposure with your camera, it is very easy and pretty accurate:
- Set your DSLR in manual mode and set the speed to 1/200 seconds.
- Select and apply a value of ISO (eg ISO 200)
- Put your flash in manual mode and adjust the power (for example, the first step 1/2).
- Set your flash to a specific distance that is the same as when you make the measurement with the Photographer Tools.
- Place a gray card or a block of white paper of printer in front of the Photographer Tools.
- Take a picture and look at the histogram, the histogram should be perfectly centered.
- If the histogram is not in the center, change the aperture on the camera to get the right aperture.

Now that you have the right aperture, record the value in the field "Aperture" (photo08, circle 2).
Also set the ISO value in the "ISO" field (photo08, circle 3).

If you made the exposure measurements on a block of white paper printers, check the "Use white paper" checkbox (photo08 arrow 3).

Now connect the Photographer Tools with a USB cable, and click the "Connect" button.
Then click on the "Get values" button (Figure 08, arrow 5).

Repeat exposure measurement for the other two measures (second measurement and third measurement).

Now click on the "Calculate" button, the program calculates the difference for each measurement
and is an average (photo08 circle 6).

Finally, click the "Upload" button, the new calibration is sent to the Photographer Tools.






I prepare another program for the "Photographer Tools" to control and pass parameters directly on Nikon DSLR cameras.
A little patience, some programs are under preparation.

I do not answer questions by email.
Please use the forum to ask questions.




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Copyright 2013 ThierryD - http://rienquepourlesyeux.free.fr
First update 17/04/2013
Last update 29/04/2013
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