Better dynamic range with ND-Fader filter?

Could you do a similar dirty test in a brighter area?
I suspect it has to do with the way the bokeh "blends" the out of focus luminance, ie. brighter parts gets blended with medium tones etc. and therefore your zebras go away earlier than without ND.
 
Looks to me like the image values are not the same between the two. The ND image is graded lighter overall. You might have to grade differently between the two approaches, but I doubt there is a real difference in ultimate DR. What do they look like if you grade to match midrange values?
 
I didn't grade at all, just threw the DNGs into photoshop and hit auto.
But since I saw it on the BMCs monitor first, I doubt it has anything to do with grading.

I think the ND might work as a lowcon filter to some degree.

For the record: I had a IR filter and the fader ND (at lowest level for the iris stop down) on the lens all the time.
 
Postmaster said:
I just stumbled over this while doing some tests.
Looks like you get better DR when using a Fader-ND filter (probably any ND Filter) than stopping down the iris.
So here is a quick and dirty test

http://frankglencairn.wordpress.com/2013/05/05/better-dynamic-range-with-nd-fader-filter/
Click to expand...

I don't know... I don't have one... So I can't really test, nor did I find a more detailed 'how does the Fader ND filter work', other than 'cross polarizing'.

I did find one reference that mentioned a non-linear response to green vs. other colors, which may fit your observation, were the 'inside the house' of your test shot, may have a higher green component, so that the shadows have more 'green' light coming through the variable filter.

Whereas the traditional ND filter is linear (that is affects all colors equal... perhaps 'flat' response would be a better term here... whereas non-linear to me would suggest a difference of response in intensity, more than non-flat response across the color 'band'...) and hence would filter out such a 'green' emphasis.

I've thought about filters that are similar to the self adjusting sunglasses, where light from the scene would induce density changes in the filter per region of 'brightness'... And I've thought about an LCD type array that would have a small lowres camera involved or a off camera feed that would analyze the scene and adjust the LCD 'pixels' to effect region based density changes.

Perhaps I could start a kickstart project... but I'm sure someone has patented that already...
 
Last edited:
I don't know if your DR has changed. Essentially a lot of averaging of light happened in your background allowing you to change the overall exposure. Like, as you mention, using a low con filter.
 
You can't increase the dynamic range of a camera with filtration. However, polarisers, low-cons, grads etc. can all help reduce the total contrast range across your frame - and therefore allow you to capture details that would fall outside of your camera's dynamic range without filtration.
 
Grug said:
You can't increase the dynamic range of a camera with filtration. However, polarisers, low-cons, grads etc. can all help reduce the total contrast range across your frame - and therefore allow you to capture details that would fall outside of your camera's dynamic range without filtration.
Click to expand...


Yep, grad NDs are amazing when shooting sunsets etcs.. won't leave home without them
 
Shooter said:
What did the waveforms tell you ...when you shot the test?
Click to expand...

Blacks are lifted a hair on the waveform.

For the record:

1. I was talking about more texture in the shadows, not the highlights, they stay the same (about 99 IRE in both shots), so we can put all that highlight blur/bokeh/distribution talk off the table.

2. Both shots had a ND fader and a IR filter on the lens, so we also can put polarizing and IR effects to rest.

Shot 1 was with the ND at lowest level and stopped down till the zebra went away.
Shot 2 was done (obviously) wide open and the ND fader dialed down till the zebras went away.

Clearly on shot 2 there is more texture in the shadows left.

My guess is, it may be one or a combination of this:

1. the ND fader doesn't lower the whole range of DR at the same level, but is more "Aggressive" in the lights.
2. the ND fade may also act as some sort of lowcon filter
3. lenses getting more contrasty when stopped down.

And yeah, of course it doesn't expand a cameras DR in some magic way, but gets you a bit more room in the blacks to play with.
Actually I don't care how it works. For my work, the results mean, that I get a hair more substance in the shadows with a fader ND, than with just stooping down.

But I usually don't use the aperture for light control anyway, mostly just the ND fader.
 
Looks like the mystery is solved, why the ND fader does that trick:

As Gerardo Campos pointed out on my blog:

The reason is very simple: is because the ND fader are made of 2 polarized filters, so when you use a polarizer you cut light from the highlights giving you more space to play in your shadows; then the 2 polarized filters from the ND Fader in first place cut the highlights and when you start to rotate it start to act in all other lights.
Click to expand...

And here is the reason why that doesn't work with traditional ND filters:

the normal ND push down all lights equally, so shadows and lights go down; but Circular Polarized filter cut only hi light, is the best filter to obtain a blue sky and a bright terrain
Click to expand...
 
I always thought that polarisers increased the contrast not decrease it. Made the blacks blacker. As for the highlight - polarisers cut-off the polarised light, do all highlight's fall into this category?
 
You must log in or register to reply here.
Back
Top