Choice of color temperature for the power LED flash module.

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fotoopa
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Post by fotoopa »

ChrisR wrote:a joystick for the lighting direction?
No, not thought to make use. I think it is less practical ( no so stable to hold into the same position). The light direction with small changes is not good visible. On the other hand, with a joystick, you could automatically calculate all values. Now with a cheap potentiometer I get just the 10 positions. I use three types of presets, 50%, 25% and 12.5% power. The exposure time is thereby 2x, 4x or 8x longer ( shift left 1,2 or 3bits of the flash time). The best experience I have is with the 25% power preset table.

I might add a small PCB with 10 LEDs in a circle on the controller front plate. In order to show the direction visually better. My LCD display does not display a good graphic symbols for this function.

Update1:
I just further examined the joystick. There are normally two potentiometers used. I would need an additional analog input to the ADC. I have 3 of the 8 inputs free. With the information from the two potentiometers you have more information for automatic computation. If the joystick is in the neutral position, there is no direction and the power is 100%. The flash time is then the default time. As you move the joystick sideways the flash must go narrower, the direction is know from the 2 potentiometers. The power can be calculated with a simple algorithm in real-time. All presets there would no longer need. Although the end result is likely to be similar, it is still a challenge. Find the correct algorithm will take some time, as well as the actual programming into the FPGA.
First order a joystick....

Update2:
Live-view has now the same light direction function support. The correct flashlight lighting direction is now already determined in live-view mode on the PC screen before any pictures are taken.

Frans.

ChrisR
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Post by ChrisR »

Some joysticks have a pot on the rotation/twist of the stick. At least they did, when I saw model aeroplanes last!

Maybe you could use it to alter the height of the gradient, or if that's elsewhere, the shape something like gamma, between these two?

Image

Or you could use a 10 armed radial star of sliders? Motorised of course so you can call up a stored profile like an audio mixing desk.. \:D/
Chris R

fotoopa
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Post by fotoopa »

Chris,

I did it simpler. I now use micro directional control, as with microstepping motors. The intermediate values are calculated. Now I get 40 calculated positions. The angle of light rotation is thus 9 degrees. This really works great! You can set the ideal lighting direction. This now also works 100% from live view mode. Everything is done in real time, you just have to turn the potentiometer. The system can also use certain shapes (via presets or manual entry from the keyboard controller) for the exposure and rotate according to the potentiometer. I'm just amazed at the proper functioning. And remember, the diffuser is a very important part in the whole setup, plus the nose inside the light module. Results: more contrast and shaper image.

Update:
I just tested my preset shapes. The calculations in real-time turn out quite extensive for the FPGA chip:
Total logic elements: 14,352 / 22,320 ( 64 % )
Embedded Multiplier 9-bit elements: 132 / 132 ( 100 % )
Extra multiplayer via the normal logic elements: lpm_mult:Mult91
But everything goes in real time even the manual input shapes. Now I have a micro-direction rotation of 9 degrees. You can easily create a profile for example, to highlight only the top and bottom. Considering the LED flash module itself remains horizontal but the camera can rotate around the tripod mount you can simply rotated your exposure with a simple turn on the directional potentiometer. You want a different shape, fill in some numbers and you have them. Manual shape is always available, a simple recall and you're back even after using a preset value. Why did they make such a simple led power flash not as a commercial product with all these possibilities? OMG I'm too old to make it commercially.

Frans.

fotoopa
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Post by fotoopa »

Here a composite picture of 40 images with each exposure rotated 9 degrees. Light is rotated in hardware and software into the FPGA realtime. Object, camera and flash do not move during this test. This just in order to see the influence of the exposure. The more bright images are a reflection of the cover glass which is positioned at an angle in order to better see the influence.
I modified the controller to automatically perform this operation. This is possible with a rotational angle of 36, 18 or 9 degrees equal 10, 20 or 40 images.
I can also see this in live view mode without shooting. This composite picture shows the effect. There are three exposure profiles via preset selectable and a manually input selection.

This is just a test, to create a full picture you need to run de normal stacking with a fix light direction after the right light direction selection in live view.

Image
Led flash with rotation 9 degree, 40 pictures by Frans, on Flickr

A larger version is available on Flickr. This is my last post on this topic. Now it's time for new stacking images.

Frans.

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Post by Chris S. »

Frans,
fotoopa wrote:This is my last post on this topic. Now it's time for new stacking images.
Thanks for bringing us along on this journey! :D Your detailed documentation is much appreciated. Looking forward to seeing your stacks!

--Chris

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