# ND Filters and Long Exposure: Calculate or Automate - That is the Question



## lilmsmaggie (Jan 15, 2015)

Seems like the best place to ask this question. I've seen references to manually calculating exposure in your head to using ND Calculator smartphone apps (e.g. LongTime Exposure Calculator for iPhone) and something called "ISO 6400 Trick," to determine exposure. 

How do you determine your exposure time when using ND filters (especially 8 stops or more?


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## sagittariansrock (Jan 15, 2015)

I use the table that came with my big stopper.


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## neuroanatomist (Jan 16, 2015)

iPhone app.


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## Tinky (Jan 16, 2015)

I compose focus and meter scene without, then use a table, a hang up from my film days because of reciprocal law failure during long exposures. 

TTL doesn't always work especially with live view, some cameras (my 7d and probably above) have two live view modes, one with applies exp simulation for preview but stil meters from actual exposure, the rebels I've owned (t2i and t3i) and the m actually meter incorrectly off of the amplified image (if you are using the picture as a guide it is wrong) and so require test shots to make sure.. not tried the 60d


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## jdramirez (Jan 16, 2015)

I haven't done one in a while, but I'd go in camera, av (with preferred aperture), & 6400 iso... then just do the math based on exposure time and iso preference. As long as the light doesn't change dramatically, you should be golden.


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## Hillsilly (Jan 16, 2015)

I use a table, similar to: -

http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/ 

What apps do people use?


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## scotia (Jan 16, 2015)

I usually calculate it in my head. It is the one bit of kit I can guarantee I will not forget at some time. I have a table written in a notebook that lives in one of my bags, but if I take a smaller bag out I do not always remember to take the notebook with me. 

My 10-stop filter is actually an 11-stop filter so the card that came with it would need me to make some adjustments anyway.


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## lilmsmaggie (Jan 17, 2015)

Hillsilly said:


> I use a table, similar to: -
> 
> http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/
> 
> What apps do people use?




Looks to be several apps available - http://appcrawlr.com/ios-apps/best-apps-nd-filter


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