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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Lens Math, help me understand....

I do have the DOFmaster for the iPhone, and the website version is WAY more up to date. It is a very good tool, just wish they'd updated the iPhone database! :)

I'll take a look at the spreadsheet for sure!

I also know there are a LOT more variables here. First, what is the native sensitivity of the 2/3. I know it is said to be slightly less than the Epic, which I believe is considered 800 now. Compared to what I am using now which is 320.

In terms of stops of light, how many more is 800 compared to 320? Would that be 4 stops more sensitive? (I only make this comparison because we are talking native ISO of the sensor, any other ISO values I understand what that means on a RED camera)
 
I am not sure how much lesser than 800 it will be. "Slightly less" sounds accurate. These things are determined much more than pixel design than pixel size/density. I think we are all likely to be surprised by how well the 2/3" performs, though I suppose we won't be able to push the ISOs as high as the M-X, thanks to the more obtrusive noise. But 800-1200 ASA range should be doable with little/organic noise, I hope.

Beyond that, yes, there are a lot of variables - from the lens design to output compression.
 
Rick Burnett said:
(snippet)

In terms of stops of light, how many more is 800 compared to 320? Would that be 4 stops more sensitive? (I only make this comparison because we are talking native ISO of the sensor, any other ISO values I understand what that means on a RED camera)
Click to expand...

Rick - I believe that the ASA/ISO scale is basically linear in terms of lighting ratios (but that doesn't translate to linear when speaking of stops). I am not sure how to best express the math in terms of stops. However, by example, the difference between ISO/320 and ISO/640 is one stop - twice the light sensitivity (just like the difference between 400 and 800 is also one stop, and the difference between 400 and 1600 is two stops with 1600 representing 4x the light sensitivity of 400).

Bumping to 800 from 320 would, I believe, be about 1.3 stops. Of course, as a reminder, one stop is twice (or half) the amount of light (depending on which way you are going) so the difference between 320 and 800 (in terms of the amount of light) is about 2 to the 1.3 power; or roughly 2.5 times more/less light sensitivity. Make sense?

(I'd actually love to hear what the specific mathematical equation is... saves me from having to figure it out!)
 
One point to remember is that it is easier to make a small f stop number lens for the smaller sensor so comparatively an a typical f2.8 zoom for s35 could be 1.5 to 2 stops faster for 2/3 and still be a little smaller - as is the case with many b4 video zooms.

Is red or anyone else going to make a b4 adapter for the scarlet that would have whatever optic is require to handle the lack of a prism? And how hard is it/what does it involve (I think I have a century b4 to cmount somewhere that I got with a surplus NASA/jpl cmount single chip camera and don't remember it having any special optic) is it just a flange focal distance issue?

I'll have to look in my various leftover drawers.
 
Michael Hastings said:
One point to remember is that it is easier to make a small f stop number lens for the smaller sensor so comparatively an a typical f2.8 zoom for s35 could be 1.5 to 2 stops faster for 2/3 and still be a little smaller - as is the case with many b4 video zooms.

Is red or anyone else going to make a b4 adapter for the scarlet that would have whatever optic is require to handle the lack of a prism? And how hard is it/what does it involve (I think I have a century b4 to cmount somewhere that I got with a surplus NASA/jpl cmount single chip camera and don't remember it having any special optic) is it just a flange focal distance issue?

I'll have to look in my various leftover drawers.
Click to expand...

Though they haven't mentioned it in a while, B4 is one of the original mount options listed in the Scarlet FAQ. It will need an optical flat with the correct refraction index to match the B4 HD standard.
 
David Rasberry said:
Though they haven't mentioned it in a while, B4 is one of the original mount options listed in the Scarlet FAQ. It will need an optical flat with the correct refraction index to match the B4 HD standard.
Click to expand...

Does that mean it is just to offset the filters in the filter wheel (much like cine zooms and wide angle primes that have rear filter slots that need a clear filter if no other filter is used) or does it also need to compensate for the prism as well?
 
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