Re: Singh-Ray Variable Density ND Filter - Feedback


"Paul Furman" <paul-@xxxxxxxxxxxxx> wrote in message
news:sZwNh.782$Rg4.157@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

What sort of situation was this? Isn't ISO 100 already pretty darn low
noise? Looks cleaner for very large prints?

Hi Paul,

A wee bit of background ...

I was reading through the excellent (and free) PBase Magazine
(www.pbase.com/magazine) and came accross (about 3 issues ago) the work of 1
Sean T. McHugh. If you don't know of him already he's one of those enviable
chaps who - just when I think I'm starting to get a few things right -
demonstrates quite modestly that I don't know *** when it comes to
photography. (take a look at www.cambridgeincolour.com) and you'll see what
I mean.

In one of his tutorials he outlined a technique of reducing high-ISO noise
by stacking identical images - so I took 32 images and stacked them with
opacities ranging from 100 (bottom) to 50 to 33.3 to 25 to 20 percent etc. I
then flattened all 32 and compared it to just 1 taken at ISO 3200. Different
as night and day. The stacking reduced it to what looked visually like about
ISO 200.

Whilst doing my long exposure shots in the weekend I took 4 with the
intention of stacking them as per the above - like you say, 100 ISO is
pretty darn good, but I wanted to see what 4 stacked would do (if anything).
I got a little side-tracked when I tried playing with the blending - I
turned off the top 2 layers and blended the 3rd to the bottom with screen
blending at 50% opacity and all of a sudden it started to look rather nice -
so I did the same with the 2nd layer from the top (at 33.3%) and it looked
even better - then did the same with the top layer (at 25%) and it looked
better again. From there I only had to give it 1 minor global tweak
(levels/gamma I think) and it was looking great. I was fully expecting to
have to use curves to lift some of the shadow detail, but it did it nicely
for me - whilst at the same time not ruining a relatively large & delicate
area getting very close to clipping at the top end.

I tried a few variations but in the end it was pretty much just the above
plus a little dodging/burning and a slight hue tweak (one of these days I'll
remember to shoot a test shot with a grey card when shooting raw!)

To be honest I still don't understand many aspects of layer blending - but
it's definately something I'll experiment more with in the future. Final
print was a 22" x 33" canvas - with sharpening a'la Sean McHugh as well (I
gave it a global 300% at 0.3 pixel just to sharpen up the high-frequency
greener/plantaion - but liked the effect of around 50% @ 15 pixels -
something I hadn't tried until now (needs to be done at LOW magnifications
to see the global effect though - I had it about 1/2 size on a 24" Dell
wide-Screen).




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