Long Exposure Heaven!

[giganova]

The solar eclipse in August gave us photographers something special: neutral-density filters with Schott glass and insane filter factors of up to +18 stops at insanely low prices. Before the eclipse such filters cost more than $400, if you could find one! Now they are around $100 in filter threads up to 77mm and above.

I'm thinking about taking advantage of this before they are gone, getting a ND 4.8 = +16 stops filter for my new 6x7 camera and wide angle lens and take loooong exposures of cool rivers, seas, skies, monuments, where all signs of life have been erased by the long exposure.

So what's +16 stops at "sunny 16"? 10 minutes exposure, 20 min?

 

[Hibbs]

This interests me too! I have a Qualcom Calcu-Lite XT meter that would be a great starting point.

Could you suggest some brand names that you would recommend? I'd appreciate hearing from you.

 

[Chriscrawfordphoto]

The solar eclipse in August gave us photographers something special: neutral-density filters with Schott glass and insane filter factors of up to +18 stops at insanely low prices. Before the eclipse such filters cost more than $400, if you could find one! Now they are around $100 in filter threads up to 77mm and above.

I'm thinking about taking advantage of this before they are gone, getting a ND 4.8 = +16 stops filter for my new 6x7 camera and wide angle lens and take loooong exposures of cool rivers, seas, skies, monuments, where all signs of life have been erased by the long exposure.

So what's +16 stops at "sunny 16"? 10 minutes exposure, 20 min?

If you're shooting ISO-100 film and you're in bright sun (1/125 at f16 with no filter) then a 16 stop ND would require about 5 minutes exposure.

 

[Bob Michaels]

Welcome to the world of reciprocity failure where you will find that a one minute exposure is far different than 60 times a one second exposure, where films like Acros 100 will require less exposure than iso 400 films, and where different color films have unexplained color shifts.

 

[Fjäll]

The solar eclipse in August gave us photographers something special: neutral-density filters with Schott glass and insane filter factors of up to +18 stops at insanely low prices. Before the eclipse such filters cost more than $400, if you could find one! Now they are around $100 in filter threads up to 77mm and above.

I'm thinking about taking advantage of this before they are gone, getting a ND 4.8 = +16 stops filter for my new 6x7 camera and wide angle lens and take loooong exposures of cool rivers, seas, skies, monuments, where all signs of life have been erased by the long exposure.

So what's +16 stops at "sunny 16"? 10 minutes exposure, 20 min?

Welcome to the world of reciprocity failure where you will find that a one minute exposure is far different than 60 times a one second exposure, where films like Acros 100 will require less exposure than iso 400 films, and where different color films have unexplained color shifts.

The entusiasm went from 100 to 0 in 2.0 seconds

 

[giganova]

Not at all. Reciprocity is easy to figure out. Just make a test with 1, 2, 5, 10, 15 min exposures and then you will know forever what the exposure time through an ND4.8 = 16 stop filter is for that particular film. Below is an example of a 10 min exposure on FP4 through a welding filter.

 

[vytasn]

I use Reciprocity Timer from Pump Interactive on my iphone, works great, even has a bellows extension calculation.

 

[brbo]

Reciprocity is easy to figure out.

Unfortunatelly, it's not.

Just make a test with 1, 2, 5, 10, 15 min exposures and then you will know forever what the exposure time through an ND4.8 = 16 stop filter is for that particular film...

for that particular light conditions!

If the light changes for a stop or two this time will not tell you much as the change in actual needed exposure will most probably not be linear.

Not to mention that for a long exposure with ND filter on film with high reciprocity failure it's virtually impossible to get the same picture as you would without ND filter and short exposure. Shadow areas require much longer correction than midtones or highlights. This might be desired (star trails for example) or not. But figuring out long exposures with film with high reciprocity failure is not easy. At least if you expect some predictability of the final results.