IR and ND Filters


Spad

Link Posted 23/09/2022 - 22:02
When I first started playing with IR I asked about using ND filters. I was told to play.... so I have!

This after I took 2 images - One with no filters and one with an ND 8 and ND 8 Grad.

Here they are...

Without



With


At the beggining there was nothing....

Which exploded....

MrB

Link Posted 24/09/2022 - 05:10
The lighting looks so different in the two shots that it is difficult to make a comparative comment.

Was there a great difference in the exposure of the two shots?

Perhaps there is a physicist on the forum who could enlighten us as to whether ND filters have an effect on the transmission of Infrared radiation or only on visible light?

Philip
Last Edited by MrB on 24/09/2022 - 05:16

Spad

Link Posted 24/09/2022 - 11:07
Oh i..... forgot to add that....

I think i took a few more too. I'll stick them on this thread and I'll also put the camera originals up to.

As you say... maybe a Professor can enlighten us mere snappers
At the beggining there was nothing....

Which exploded....
Last Edited by Spad on 24/09/2022 - 11:08

Lubbyman

Link Posted 24/09/2022 - 12:48
Interesting. I prefer the second 'with' shot (although I'm still not a fan of IR!).

Guessing here at the reason for the apparently different lighting and assuming an ND reduces IR as well as visible light... The position of the clouds is much the same in both pictures so the time between shots must have been fairly short and natural light (actually, IR light) much the same in both. The skies look to be much the same brightness/darkness with and without the ND grad (albeit a bit darker with the filter) so the shot with the ND grad must either have been exposed for longer or brightness adjusted in post-processing. Either way, the effect on the foreground (which did not have light/IR reduced by the ND grad) is to increase its brightness. How's that ?

Steve

MrB

Link Posted 24/09/2022 - 18:04
Interesting analysis, Steve. It just seems that perhaps the different lighting in foreground and background could be the effect of clouds moving over the sun, blocking the IR much more than the ND filter would? In the absence of 'expert' comment so far, we might have a better idea of the effects of ND filters if we knew the exposure parameters for each shot.

Cheers.
Philip

cardiffgareth

Link Posted 26/09/2022 - 19:05
I think Philip has it here as the light is hitting the foreground in one and the middle ground in the other.

Love how the skies go when shooting in IR on a bright blue sky day
Gareth
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