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Posts posted by herbko

  1. I'd love to see a modeling light that uses these 100 lumen LEDs. Halogen modeling lights need to go away. The way I figure, a 20W halogen modeling light can be matched in output by 4 of these LEDs at 1/4 the power drain and that would enable effective use of AA batteries. The beam might not be as wide but modeling lights are best with moderately wide beams anyway. 4 LEDs and 4 AAs would provide 2.5 hours of burn in a tiny light.


    For a modeling light, the CRI is not a big deal. Actually I sometimes wish for one with red LEDs which would be less disruptive to the critters. I tried using a red filter on a white LED light and found almost no red light coming out. That was what got me starting looking into the output spectra of these LEDs.

  2. Has there been other work on making videos with a white LED as a light source or are we breaking new grounds here? I would be concerned with the spectral output of the white LED. Here's a reference to the devices I'm familiar with.




    Maybe the L&M ones are something different.


    If the spectrum of the LED is like the one in the above reference, you'll only get to use a small percentage of the light by the time you filtered and white balanced for a day light spectrum.

  3. If nothing else the 21MP will make the Dx crop or digital zoom feature that Nikon will put in more useful.


    The advantages of the 12MP are cost and speed and most importantly better signal-to-noise and dynamic range. The cost in the required larger storage is negligible. If speed is not a factor to you then the only trade-off is the lost of about 1/2 stop in signal-to-noise and dynamic range.


    You lose about a factor of 2 in signal-to-noise in making the photosites 1/2 as big. However, if you down sample back to the lower resolution you'll get 1/2 of that the back. So for a given print resolution doubling the number of photosites will only cost 1/2 stop in noise and dynamic range.

  4. Watt-sec is a measure of the electrical input. We're interested in the light output. The efficiency in converting electrical energy to light can vary by more than a factor of 2 for incandescent sources and is very sensitive to filament temperature which also determines the color of the light output. Lower temperature, redder sources are much less efficient. See for example:



  5. I don't think a modular digital camera ever made any sense. There has to be lots of design compromises to make it work, and I doubt any camera maker wants to be held back by an old set of controls when they may have new features like live view to implement.


    Except for a tiny number of underwater photographers, it probably does not even make economic sense for the user. He's probably better off selling the old one on ebay and buy the new one than to paid the cost of upgrading sensor, processor, and memory.

  6. Find a container slightly bigger than your camera setup.

    Put camera in container.

    Put container on scale.

    Fill with water until overflow and note the weight.

    Take the camera out.

    Fill with water until overflow and note the weight again.

    The difference in the two measurements is how much your camera is negative.


    EDIT: I just read the rest of the thread more carefully and noticed Steve had a similar idea. This way you don't need to make any volume measurement. You only have to read the scale. You can get .1 lb precision with a $30 scale.


  7. How about instead of building housings, specialize in ports. Be the Sigma and Tamron analog in the underwater housing market. I think there's a sizable demand for ports not offered by the all the housing makers. I would buy a smaller dome and smaller macro port for my Aquatica housing if such were available.


    You can do what the lens makers do and sell your ports in all the popular housings or make adapters for the other housing to fit your mount.

  8. One way to compare the strobes is to look at the bang you get for the weight in air of the strobe. I think higher GN/weight is better and it's better to make buoyancy adjustments in places other than the strobe. Of course you have to take into consideration the width of the beam and it's uniformity.


    It does seem clear from theory and practice that you paid at least a factor of 2 in output power/weight for the redder color output of the Ike strobes.

  9. Good information. It looks like it's true that the Z-240 is significantly brighter than the DS-125 at least at the center. The weight information is very welcomed. Although, it's an important consideration, there are advantages to small strobes. Smaller size sometimes give you more freedom in strobe placement.


    If you asked me the question: where would you add volume to your setup to make it more buoyant, I probably would not choose to increase the size of my strobes.

  10. I am curious as to what others think. This 40D looks aweful nice. I had been waiting for the 5D replacement to get Full frame and have many of the features of this 40D. Because of the Tokina 10-17mm do people feel the relevance of the Full frame is not a crucial point of difference now?


    That and something like the Aquaview from Aquatica sure make this tempting.




    The 5D is significantly better at sunball shots than the old 300D. I don't know how it compares to the 20D or 40D.

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