Determining EV using a table

[Antonio Correia]

Let's see if I can explain myself in what I was expecting from an app to iPhone returning long exposure values. (more than 30 seconds)

When I shoot during the night in poor light conditions and I want to make loooong exposures I find that my camera stops at 30" as maximum.

As I want to keep the Exposure Value (EV) correct I am needing a way to calculate it with precision.
I downloaded two programs from the iTunes and I found them not doing what I wanted.
Shame: one of them stopped at 30 seconds !
May be it's just me or my ignorance or... both.
I understand that it is not practical to have to keep looking among a couple of situations looking for what is supposed to be the right EV.

Let me give you a quick example:
I am on the field and I read the light and it goes like this:
ISO 100 - 15 sec exposure - f/4

But if I want to use f/11 I must change the other parameters.
I light my torch on the iPhone because it is dark and take my table from the pocket and read that I have to change the exposure to 2 minutes keeping the ISO

I was expecting that the apps would help me but just confused me until I decided to build this table. I am only showing you a small part of the table as it is much broader...

Any corrections ? Am I wrong ? Where ?

http://antoniocorreia.smugmug.com/photos/935999738_AQTbQ-M.png

[Blackwood]

To be honest, I find the format confusing. The first 5 columns are clear.

I know what you are trying to do with the next 7 columns (relate apertures between 2.8 and 22 back to 16 in terms of relative stops).

What I'm not clear on immediately is how you're using them together. I can't follow your arrows.



I made a table with a similar purpose a while back (attached). I set it up for use with my 6-stop ND and 2-stop CPL filters, with the potential to open up one stop.

In practice found myself just pulling out a calculator.

6 stops down means I need to double the exposure 6 times over. 2*2*2*2*2*2 = 2^6 = 64. So a 1 second exposure is now a 1 minute exposure.
8 stops down means I need to double the exposure 8 times over. 2^8 = 256. So a 1/4 second exposure is now a 1 minute exposure.

[DavidTO]

Antonio, I've moved your post, since it's not really about shooting with the iPhone, but is better suited to this forum. :thumb

[Antonio Correia]

Antonio, I've moved your post, since it's not really about shooting with the iPhone, but is better suited to this forum. :thumb


Well done David Thank you :D