any IOS app for averaging two exposures out there?

peterB1966 · Jun 3, 2021

Anybody know of any apps that don't just convert one exposure to another of the same EV (there are plenty of those), but one that takes two readings of different EVs, and gives me an average?

I find it really frustrating when I meter off backlighting and then need to average it with the incident reading in front of the subject, but my meter gives the one at X-and-a-half and the other at Y-and-a-third ... it's a real bottleneck on my setups, while my brain melts.

Chan Tran · Jun 3, 2021

peterB1966 said:
Anybody know of any apps that don't just convert one exposure to another of the same EV (there are plenty of those), but one that takes two readings of different EVs, and gives me an average?

I find it really frustrating when I meter off backlighting and then need to average it with the incident reading in front of the subject, but my meter gives the one at X-and-a-half and the other at Y-and-a-third ... it's a real bottleneck on my setups, while my brain melts.

Convert both to EV then average the EV then convert back to setting. But if your meter read half and another reads third it would be difficult to do program an app for that.

peterB1966 · Jun 3, 2021

Chan Tran said:
Convert both to EV then average the EV then convert back to setting. But if your meter read half and another reads third it would be difficult to do program an app for that.

I find it hard to believe an app could not come up with a answer, even if the answer is, eg. "between F8 + 1/3 stop and F8 + 1/2 stop"...

That said, you make it sound like a simple process to convert them to EV, but as far as I can find you need to use a mathematical table involving logs, powers and bases which, if my brain wasn't melting before, would ensure it steamed! Or am I missing something, and there is an easier way of doing it (such as maybe perhaps an app)?

Chan Tran · Jun 3, 2021

peterB1966 said:
I find it hard to believe an app could not come up with a answer, even if the answer is, eg. "between F8 + 1/3 stop and F8 + 1/2 stop"...

That said, you make it sound like a simple process to convert them to EV, but as far as I can find you need to use a mathematical table involving logs, powers and bases which, if my brain wasn't melting before, would ensure it steamed! Or am I missing something, and there is an easier way of doing it (such as maybe perhaps an app)?

No once you have the EV number it's simple math. For example the average of EV 15 and EV 11 is EV 13 that is (15+11)/2. That is why say convert the f/stop, shutter speed to EV first. Average the 2 EV numbers then convert it back to f/stop and shutter speed.
For me I just do it in my head. But again I would use the thirds as I don't know the shutter speeds and aperture values in half.

peterB1966 · Jun 3, 2021

Chan Tran said:
No once you have the EV number it's simple math. For example the average of EV 15 and EV 11 is EV 13 that is (15+11)/2. That is why say convert the f/stop, shutter speed to EV first. Average the 2 EV numbers then convert it back to f/stop and shutter speed.
For me I just do it in my head. But again I would use the thirds as I don't know the shutter speeds and aperture values in half.

Thanks - the averaging part looks really simple, what I meant was the process to arrive at the EV itself, before averaging

I presume it would be best to have a chart handy (to convert e.g. two exposures of e.g. f2.8 @1/1000th and F2.8 @ 1/250th to EV13 and EV11, hence two stops difference, divided by two gives me one)?

Chan Tran · Jun 3, 2021

peterB1966 said:
Thanks - the averaging part looks really simple, what I meant was the process to arrive at the EV itself, before averaging

I presume it would be best to have a chart handy (to convert e.g. two exposures of e.g. f2.8 @1/1000th and F2.8 @ 1/250th to EV13 and EV11, hence two stops difference, divided by two gives me one)?

That is correct your result is EV12. To convert f/2.8@1/1000th to EV13 in my head this is what I do.
Memorize the aperture value and shutter speed value. For example f/2.8 has the value of 3 and 1/1000 has the value of 10. It seems difficult at first but after a while you remember them by heart. Once you know the full stop values the 1/3 values can be deduced.
For example now that we determine that the exposure would be EV12. We want to use f/5.6 which has the value of 5 so the shutter speed value must be 8 which is 1/250. Or you can keep f/2.8 which has the value of 3 and the shutter speed of 1/500 which is 9.

peterB1966 · Jun 3, 2021

Chan Tran said:
That is correct your result is EV12. To convert f/2.8@1/1000th to EV13 in my head this is what I do.
Memorize the aperture value and shutter speed value. For example f/2.8 has the value of 3 and 1/1000 has the value of 10. It seems difficult at first but after a while you remember them by heart. Once you know the full stop values the 1/3 values can be deduced.
For example now that we determine that the exposure would be EV12. We want to use f/5.6 which has the value of 5 so the shutter speed value must be 8 which is 1/250. Or you can keep f/2.8 which has the value of 3 and the shutter speed of 1/500 which is 9.

Ha ha, mind melting again, but this is great - you are giving me a way of carrying the conversion process inside my head.

You mention the exposure values associated with different fstops and speeds, but where does one get these values? I can see that they change with each stop, but is there a table I can refer to in order to internalise the scales?

Chan Tran · Jun 3, 2021

OK
You would have to memorize it
Aperture Values:
f/1.0=0
f/1.4=1
f/2.0=2
f/2.8=3
f/4.0=4
f/5.6=5
f/8,0=6
f/11=7
f/16=8
f/22=9
f/32=10
etc...
the formula is log(f number ^2) / log(2)= Aperture Value but don't use the formula because the way the aperture is conventionally rounded off the numbers don't match exactly. Just memorize them.

Shutter Speed Values
Again start with 1 and 0
1s=0
1/2=1
1/4=2
1/8=3
1/15=4
1/30=5
1/60=6
1/125=7
1/258=8
1/500=9
1/1000=10
1/2000=11
1/4000=12
1/8000=13
etc...
Again the formula is log(shutter speed) / log(2) for example log(1000)/log(2)= 9.96 because the shutter speed is really should be 1024 so just memorize them don't use the math.
Also it's possible to have negative values for example 2s is -1 and f/0.77 is -1 also.

Pieter12 · Jun 3, 2021

Get a meter that reads in EVs.

grain elevator · Jun 3, 2021

I think you're all overcomplicating this. Match your two readings to either the same shutter speed or the same aperture. Average the other. Easy, no need to convert to EV. Averaging can be made super easy by just finding the graphical middle value on the aperture or shutter speed dial, or counting fingers.
Using the average is sort of arbitrary anyway, no need for excessive precision. Or you could find a way to meter that doesn't require any of this, should be possible for negative film at least.

BrianShaw · Jun 3, 2021

Pieter12 said:
Get a meter that reads in EVs.

Amen!

peterB1966 · Jun 3, 2021

Ok, I‘ve had my incident meter less than a week so still learning, but yes, it does have an EV meter, just not in the same screen as the reciprocity meter... but yes, makes sense: use it to get the difference, take incident reading of subject , and add half the difference. Method cures madness

Nonetheless, @Chan Tran - thanks for the patience and all the detail, this has helped clarify a lot for me, and I will def be saving your table!

Chan Tran · Jun 3, 2021

peterB1966 said:
Ok, I‘ve had my incident meter less than a week so still learning, but yes, it does have an EV meter, just not in the same screen as the reciprocity meter... but yes, makes sense: use it to get the difference, take incident reading of subject , and add half the difference. Method cures madness

Nonetheless, @Chan Tran - thanks for the patience and all the detail, this has helped clarify a lot for me, and I will def be saving your table!

Which model of the meters do you use? Both the incident and reflective. I could write a program to do what you want with the PC or even my programmable calculator but I never tried to make an apps on the smart phone so I don't know. But 1 thing I know I would like to keep the 2 reading either in half or in third and not mixed.

radiant · Jun 3, 2021

Many light meter apps show the value in EV. Just measure the two different EVs and calculate the average?

MattKing · Jun 3, 2021

And even if your meter uses another, more arbitrary scale, just pick the number halfway in between.

Pieter12 · Jun 3, 2021

Minolta meters have (had?) memory functions with a graphic display of the f-stop, you just pick the half-way point.

benveniste · Jun 3, 2021

I do have a widget from Luxi, which, when combined with a Light Meter App, will let my iPhone function as an incident meter, but I don't know of any dedicated averaging app.

peterB1966 · Jun 4, 2021

Chan Tran said:
Which model of the meters do you use? Both the incident and reflective. I could write a program to do what you want with the PC or even my programmable calculator but I never tried to make an apps on the smart phone so I don't know. But 1 thing I know I would like to keep the 2 reading either in half or in third and not mixed.

I have the Polaris - unfortunately it doesn’t display the scale (like the Minolta example above, a meter that came available at the same price a few days after I bought the Polaris, sadly), so i need to visualise the scale each time. Coming from digital this is a new requirement that I have to master

DMJ · Jun 4, 2021

peterB1966 said:
Anybody know of any apps that don't just convert one exposure to another of the same EV (there are plenty of those), but one that takes two readings of different EVs, and gives me an average?

I find it really frustrating when I meter off backlighting and then need to average it with the incident reading in front of the subject, but my meter gives the one at X-and-a-half and the other at Y-and-a-third ... it's a real bottleneck on my setups, while my brain melts.

Yes, but unfortunately not for iOS. AP Light Meter for Android gives you the difference in EV of two readings and an average shutter speed of three readings.

https://www.lamultimedialab.com

RalphLambrecht · Jun 4, 2021

peterB1966 said:
Anybody know of any apps that don't just convert one exposure to another of the same EV (there are plenty of those), but one that takes two readings of different EVs, and gives me an average?

I find it really frustrating when I meter off backlighting and then need to average it with the incident reading in front of the subject, but my meter gives the one at X-and-a-half and the other at Y-and-a-third ... it's a real bottleneck on my setups, while my brain melts.

I don't knowof any but, isn't that very simple to do in your head?

peterB1966 · Jun 4, 2021

RalphLambrecht said:
I don't knowof any but, isn't that very simple to do in your head?

OK, this has come full circle

In my initial query I mentioned the situations where "my meter gives the one at X-and-a-half and the other at Y-and-a-third", which was def causing problems. Reading it as EVs and averaging those definitely solves the problem, it was just a cognitive next-step I needed to understand, as the EV reading on my meter does not display on the same screen as my aperture and shutter reading.

rupalimittra · Jun 9, 2021

Average Camera Pro
I have been using this app for years and for blending many exposures over a long time, it is unmatched. Lots of control over number of frames and timing between photos. This said, the UI is dated and it does not offer any access to more than the standard lens on multiple lens iPhones which is very disappointing at this point. I would gladly pay to get this app updated with latest features and functionality because even without these updates, it’s still very good.

peterB1966 · Jun 22, 2021

rupalimittra said:
Average Camera Pro
I have been using this app for years and for blending many exposures over a long time, it is unmatched. Lots of control over number of frames and timing between photos. This said, the UI is dated and it does not offer any access to more than the standard lens on multiple lens iPhones which is very disappointing at this point. I would gladly pay to get this app updated with latest features and functionality because even without these updates, it’s still very good.

Thank you - I will def look into it!

peterB1966 · Jun 22, 2021

rupalimittra said:
Average Camera Pro
I have been using this app for years and for blending many exposures over a long time, it is unmatched. Lots of control over number of frames and timing between photos. This said, the UI is dated and it does not offer any access to more than the standard lens on multiple lens iPhones which is very disappointing at this point. I would gladly pay to get this app updated with latest features and functionality because even without these updates, it’s still very good.

Hi, took a look at this - I see it does blended exposures on your phone, but it's not immediately clear if it actually allows you to enter two exposures and coughs out an averaged result?

any IOS app for averaging two exposures out there?

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