So I finally got this project moving. The shop at work had extra pelxi that's close the the right thickness (might be too thick, but I don't recall the thickness being crucial in the holder?). So I had them rip me 3 square panels and took them to a local tint shop. I asked for a sample/scrap of their darkest, truest black tint which he gave me no problem. Took it out to the car and did the sunny 16 rule with it and got:

with tint: 1/125th, f16, 1600
w/o tint: 1/125th, f16, 100

so that's four stops right:
100->200
200->400
400->800
800->1600

it also looked very neutral outside in daylight, so if it's not, a CWB should fix it anyway...

I had him tint both sides for me which should make it an 8 stop filter yes? I had three panels and asked him to do all three. He's charging me $30, so $10 each. Not sure why I even bothered with all 3, but it seemed like one would be to small to even ask...

He warned me "over time" these could blister or discolor in general and also because of the plexi, but I told him they'd see maybe 5 hours of sunlight in their entire life. If this works, I may go get real glass from lowes and try that and maybe even some museum glass from Jerry's. But so far these are well under $10 each and this is the X pro size.

IB"ben'sfilters"makeshimrich!

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Nice! I'm anxious to hear how they work!

How "sealed" to light is your holder? Is there a gap between the filter and the lens?

I love it Ben, that's even more frugal than me!!!

well the ring to the back is pretty well sealed. The CP to the front is as well (except for the fact light goes THROUGH it ). The ND can go in front of the CP (which should put me around 9 stops?) and there will be a small gap in between OR I could remove the CP and stack 2 of these for ~16 stops?

I'm thinking I'll be able to easily fix any sealing issues with gaffers/black masking tape though. Plus, it should just be 2 strips, one up top and one on the bottom right (assuming the sides of the holder won't be an issue)?

Originally Posted by PhatheadWRX

I love it Ben, that's even more frugal than me!!!

you do realize you CAN'T buy these even if you wanted too right?

and I have an email in to format to see if they'll custom make one... I also sent one to cokin but got the reply already:

Dear Ben,

Thank you for your enquiry. The 156 (NDX) has been discontinued since earlier 2008, the filter was also only manufactured in P series. Unfortunately Cokin don't take on special commissions to make specific filters.


Best regards,

Simon

Sales Office.

but yeah, I would have DIYed one before paying anyway because I KNEW this would be cheap...

I am interested to see how this turns out.

Originally Posted by jacobsen1

well the ring to the back is pretty well sealed. The CP to the front is as well (except for the fact light goes THROUGH it ). The ND can go in front of the CP (which should put me around 9 stops?) and there will be a small gap in between OR I could remove the CP and stack 2 of these for ~16 stops?

I'm thinking I'll be able to easily fix any sealing issues with gaffers/black masking tape though. Plus, it should just be 2 strips, one up top and one on the bottom right (assuming the sides of the holder won't be an issue)?

Sounds like you've got it worked out pretty well! I've tried 14 stops a few times now and it's really difficult to get the exposure right. I'll usually calculate it out and then be off by a stop - and have to shoot again. I notice a lot of color shift as well - might be infrared related?

here's an untouched 4-minute shot at bryce to give you an idea of what i mean. I'm not sure if a custom whtte balance would take care of it.



Clean those filters! Yikes!

Ha, just doing a little math - if you're shooting at scene that calls for 1/125 without the 16-stops of filter you'll need to shoot it at ~520 seconds.

That'll be fun for you.

Originally Posted by MoLS

Ha, just doing a little math - if you're shooting at scene that calls for 1/125 without the 16-stops of filter you'll need to shoot it at ~520 seconds.

That'll be fun for you.

thats sick.

sunny 16 to NINE MINUTES!

I'm not even sure if I'm doing the math right. When I do it I always seem to be a stop under. I'm gonna do some experimenting right now...

1:125th
2:60th
3:30th
4:15th
5:1/8th
6:1/4
7:1/2
8:1s
9:2s
10:4s
11:8s
12:15s
13:30s
14:60s
15:120s
16:240s

that's the "right way" using camera math, but the issue there is with jumps from 1/125th to 1/60th and 8s to 15s that aren't even... Those could be throwing your math off by the stop....

edit: yeah, I just did the "math" way using .008 for 1/125th and doubling that 16 times. You end up with 524.288s that way -vs- 240 doing it using "photo math". So maybe that's your issue? I'd have to go test it both ways I guess to really figure this one out.

I've been doing it as a "filter factor."

So for my 14 stops - it's 2^14 = 16,384 as the factor and then I multiply the unfiltered exposure by that.

So I metered a shot at 1/100 just now and then exposed it for 164 seconds, but it was underexposed. I'm trying 328 seconds now.

weird, I would have thought your way would OVER expose....

hopefully it's at least consistent, whatever it works out to be....

So from my little experiment here - I needed 2^15 = 32,768 times more exposure for my "14-stops" of filter.

Excuse the hideousness of my long exposures using ISO 3200...
(the red shift is ridiculous at this high iso)

Metered scene, no filter - 1/100


Scene using original 2^14 filter factor - 164 seconds


Scene using 2^15 filter factor - 328 seconds


So it seems that you'll need to have a FF of 2^17 or so for your 2x8-stop setup. Yikes.

Originally Posted by MoLS

So from my little experiment here - I needed 2^15 = 32,768 times more exposure for my "14-stops" of filter.

Excuse the hideousness of my long exposures using ISO 3200...
(the red shift is ridiculous at this high iso)

Metered scene, no filter - 1/100


Scene using original 2^14 filter factor - 164 seconds


Scene using 2^15 filter factor - 328 seconds


So it seems that you'll need to have a FF of 2^17 or so. Yikes.

What filter are you using? That red cast is odd.

This is with the B+W 10-stop filter and a hi-tech 4 stop p-size.

I'm thinking that it's an infrared issue, Shawn. I don't think ND filters pay particular attention to IR. Neither of these filters have shown a cast when I use them separately. Together they make for such long exposure times that the IR is getting through the high pass filter over my sensor. The high ISO of those shots is definitely making it worse, as well.

The good news is that I can clean it up mostly in post, so a custom WB might work but I'm not sure how you'd set it with this much filter.

Originally Posted by MoLS

I'm thinking that it's an infrared issue, Shawn. I don't think ND filters pay particular attention to IR. Neither of these filters have shown a cast when I use them separately. Together they make for such long exposure times that the IR is getting through the high pass filter over my sensor.

The good news is that I can clean it up mostly in post, so a custom WB might work but I'm not sure how you'd set it with this much filter.

OH, i am a dork. Didn't realize you were stacking, yeah that can be an issue.

Jeff, you say 2^17, but show 2^14 and 2^15 right? 2^15 looks pretty good to me, if not overexposed slightly? The corners are darker, but I'm guessing that's just an issue with this much filter?

2^17 would be my best guess for you and your 16-stops - but you're definitely going to have to experiment.

The dark corners show up in all my stacked filter shots - it could be lens related, too.

Originally Posted by MoLS

2^17 would be my best guess for you and your 16-stops - but you're definitely going to have to experiment.

gotcha, I thought you meant for your test shots...

so, yeah, take the stops of the filters then overcook it one stop, yes?

Yeah, I think that's right as long as you're using real math and not "photo" math.

I'll compose a scene in shutter priority with a good round number like 1/100 or 1/200 etc and then roughly multiply that by the "filter factor" (2^(n+1)) and keep the same aperture it told me without the filter. Pretty easy for 10-stop shots since it's 2048, tougher to do in my head for 14-stops - 16 should be really fun... (cell phone calculator ftw)

Originally Posted by MK19

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+1

I take it you're gonna try these on Sunday at Sachuset?

sure. Honestly I haven't needed/been using my 10 stop a lot in the mornings as I like what I get with the CP and or no filter during twilight. But I'll have them with me and I hope to have tested them either tonight or tomorrow.

Well I tried it with MoLS's technique, same settings, and taking into account the grad and solid for me, 12 stops. And it seems the overcook 1 stop works.

-Andy

For me though if I had a 1 second exposure with the solid on and 3 stop GND, it would be 4096 sec, which is 68 minutes. I guess I won't use this much in the AM until the sun is up.

OK, initial tests are pretty crappy. Obviously there's a bit of a cast, but the issue is it's not one even color. But from when I got my windows in my car tinted in MT I remember that drying in a few days, so I'm not giving up just yet....

it's also visible to the eye under the right light too, so I KNOW it's got to go away...

OK, I took some shots this morning with one and two. One seems pretty good (a bit red?) but two went to **** in a hurry... But I forgot my tape, so I'm thinking it was reflections between the two layers. I should have shots up later (and I also shot my real 10 stop so I could compare).

OK, looks much better today, so I'm hoping they "cure" with a consistent color...

w/o anything (1/8, f/13, 100):


DIY (30sec, f/13, 100):


DIY (30sec f/16, 100):


"real" 10-stop (30sec, f/16, 100):


2 x DIY (30sec, f4, 400):


so it's looking like ~8 for one and not quite 16 for two. But there are obvious light leaks (I forgot my tape) between the filters there which will mess with that anyway. Looks promising, but if they don't get more consistent they won't be more than a fun toy really... but in use, god damn do I want a working 10 stop rectangular filter... So much easier to use.

Definitely look like one works pretty well.

I can imagine that a single filter would be a lot more convenient than screwing on a filter after composing each shot...

yeah, the issue is with the zebra color patterns in the sky....

but yes, sliding the panel is works SO well. Basically, when I'm shooting landscapes, the holder is on the lens, so to pop in a filter is easy, taking the holder off to screw on the ND is a PITA.

I'm also wonder if the color issue with the sky is due to light leaks on the single? It has a gap as well???

What about the edge of the plexi? Is that tinted as well? I could see that causing some weird issues if it isn't.

Damn, using just one works out really well. Using 2 gives you a weird novelty effect. Interesting. Now, screw the 10 stop filter to the lens, the Cokin holder to the filter and put one DIY in front of the 10 stop.

^ shawn, I had ZERO tap on the stacked filters, so I'd bet "sealing" them will result in a working 16 stop filter on it's own. I suppose I could stack those OVER the real 10 stop for ~26 stops though?

Originally Posted by jacobsen1

^ shawn, I had ZERO tap on the stacked filters, so I'd bet "sealing" them will result in a working 16 stop filter on it's own. I suppose I could stack those OVER the real 10 stop for ~26 stops though?

Yeah, That would be awesome for shooting a busy area mid day and seeing no people in the shot. But the exposure would be craaaaaaazy long.

w00t!

Hi Ben,

Yes we can make this 130mm x 130mm x 1.5mm thick. The price would be
£76.60.

Regards
Cerianne

so if this doesn't work, I can buy one for ~$130.

no, I have to remove the CP to fit 2 filters.