Lee filters with LF lenses and ultra long exposures

[cdavis324]

However you do it, you should seal every joint. Around the lensboard, bellows frames, film holder, removable back, holder light trap. I’ve never done anything in the range of what you’re talking about, but regularly do 1 hr exposures. I used to use a chamonix with wide angle bellows(the bellows material is completely light tight, btw), but always tape every joint - considering the time I put into each picture it seems like good insurance to me. I’ve yet to receive my new camera, but hope it’s as light tight! And I never covered the bellows/camera with a dark cloth - I’d be more worried about the vibration it could add(although would be a great solution in non-windy environments).

Vibration is another problem you’ll have - I use an aluminum gitzo 5 series with a majestic head and a couple sand bags for good measure...

Good luck!

You don’t need anything as “aggressive” as tape. A simple strip of black foam will do the same and it is reusable.

Just slide it in/over/between where required.

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[Eric Woodbury]

A nice tutorial at BH

https://www.bhphotovideo.com/explora...ensity-filters

I wouldn't stack more than 2 filters, not only because of image quality, but they won't add the way you think they might.

If you are aware of a big disturbance approaching during exposure, you can put a black card in front of the lens to interrupt the exposure. However, unless the disturbance lasts a long time, you'll never see it.

Sounds like fun.

[Tim V]

Thanks all for the great replies!

I wasn't aware that there were alternatives to the Lee filters, and it's the first I've heard of ND filters used for astrophotography. Any tips on where to look for them? I'm guessing they're expensive?

I've never done made exposures anywhere near the length I mentioned either, hence it's a real mystery to me how I might go about it. I've come to wanting to do it for conceptual reasons more than anything, but I'm just as curious about the results on an aesthetic level as well.

Seems like I should try and avoid stacking filters. Lee do a ND4.5 / 15 stop in the Pro IRND line, but that won't be strong enough. It'll get me in the ballpark though, as once I compensate for reciprocity failure I'm getting towards 6 hours with a 100iso film like Ektar (if I'm being optimistic.) I don't mind over exposing a few stops, so maybe I'll be okay? I want to use colour film for this, and work with the cross curves etc to heighten the shifts of light.

I did assume that I'd need to take out sheers in a gaffer tape company... This is where my Kiwi ingenuity should come to the fore... I'm expecting a lot of hic ups along the way, but should be fun.

Keept the tips and thoughts coming!

[Eric Woodbury]

With color, won't there be a tricky color shift since the different layers have different reciprocity failures?

Here's 7.2

https://www.bhphotovideo.com/c/produ...m_neutral.html

I don't know the ND factor here

https://www.amazon.com/Solar-Filter-.../dp/B00DS7S52W

[Tim V]

I've found a few that might be suitable...

Namely this one: LINK

Anyone have experience with the Formatt brand filters of this level? They go all the way up to ND 7.2! I'm thinking that once compensating for shifts of light; soft light in the morning and fading light at the end of the day, a 18 stop / ND5.4 should be ample. If I were to be conservative and accept over exposure, the 16 stop / ND 4.8 might be good too. I'm basing this on setting the camera up, using 100ISO film and stopping down to f45 or f64. At exposures of this length, the negative effects of diffraction are the least of my worries...

Lee also make this 20 stop ND for solar photographer : LINK

What do the brain trust reckon?

T

[Tim V]

Thanks for the links.

Yes, I'm fine to work with those shifts as part of the process. Kind of like them in some instances, although accept it might get a bit funky when pushing the exposure that far.

I will try with BW film too, but I'm interested in emphasising the shifts of light with colour. I'm going to need to make friends with a top notch drum scan operator, I fear...

Thanks again,

Tim

With color, won't there be a tricky color shift since the different layers have different reciprocity failures?

[neil poulsen]

It might just be simpler and easier to use a pinhole instead of a lens!

If you use a pinhole, you'll need a center filter.

[neil poulsen]

Stacking can be problematic, with light reflecting between adjacent filters, etc. Consider putting one filter on front and another on the back of the lens.

[cdavis324]

You can’t really predict what will happen with long exposures - you just have to start trying. It doesn’t work to mathematically project reciprocity when you get past a few min. At some point the light hitting the film won’t be enough to record any image at all(in spite of what the math says). You may want to consider some type of pre- flash for the film, so you can make sure an image is recorded... especially if you’re using really dark filters. You have to have enough light hitting the film to get over the toe - otherwise it doesn’t matter how long the exposure is.

I would try starting with the darkest wratten filter you can find and then you have some data. It will probably surprise you and you can go from there.

Ektar is fairly tolerant to exposure variations, but portra will give another few stops... especially if scanning.

There’s no need for expensive IR filters for film - there are a lot of used non-IR filters out there with digital shooters switching over. You can even start with a welding filter which is approx 14 stops and green, but will give you an idea of what you’re getting in to for cheap.

Good luck!




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[Drew Wiley]

One thing you'll discover is that most ND filters aren't really neutral when it comes to fussy color applications. Some can be a bit greenish. And at exceptionally long exposures, you'll have other unwanted surprises. I strongly recommend doing a series of exposure tests with cheap 35mm film first.
Flashing is tricky. But you can do it employing a diffused warming filter to offset the tendency of Ektar to go unduly blue under such circumstances. Aim for a flashing exposure equivalent to Zone III against a blank neutral gray target.