Ev numbers mean what/backwards on preview?

[Brandon]

This may be an overly basic question, but what exactly do the EV numbers equal? Looking at the image tab they appear to match a mix of shutter speed and aperture and likely ISO, though I have not tested it to much.

Bigger numbers let more light in and smaller numbers let less light in. That is simple and makes sense to me.

That theory gets shot up when looking at the fast preview and changing the EV there. Bigger numbers make the final pano darker and smaller ones are brighter. Why does the EV scale go backwards depending on where you are looking? This makes things very confusing when telling someone to brighten something by one EV number and no one can remember which way is brighter as it all depends on what a person is adjusting.

[bugbear]

Brandon wrote:
> This may be an overly basic question, but what exactly do the EV numbers equal?

http://www.kenrockwell.com/tech/ev.htm

BugBear

[Brandon]

That is a great read, thanks for the link. I am not sure it answers my second question though. Why is the fast preview EV number backwards from the EV on the images tab when you try and change it?

[T. Modes]

Am Mittwoch, 3. Dezember 2014 09:46:01 UTC+1 schrieb Brandon:

Bigger numbers let more light in and smaller numbers let less light in. That is simple and makes sense to me.

That's wrong.
Smaller numbers mean longer exposure time and/or brighter aperture (smaller f-stop) and therefore more light -> brighter images (of the same scene).
Bigger number -> shorter exposure time and/or closed aperture (bigger f-stop) -> darker images.

[Brandon]

On Thursday, December 4, 2014 9:02:07 AM UTC-8, T. Modes wrote:

Smaller numbers mean longer exposure time and/or brighter aperture (smaller f-stop) and therefore more light -> brighter images (of the same scene).
Bigger number -> shorter exposure time and/or closed aperture (bigger f-stop) -> darker images.

That makes sense as well. That is the way it works on the fast preview. On the image tab though if I increase the EV number the image gets brighter instead of darker. I wonder why?

[Bruno Postle]

On 5 December 2014 at 01:08, Brandon <bra...@flyingtsalers.com> wrote:
>
> That makes sense as well. That is the way it works on the fast preview. On
> the image tab though if I increase the EV number the image gets brighter
> instead of darker. I wonder why?

If you set the output Ev in the preview to the same number as the
input Ev for a photo, then the effect is no overall brightness change.
So when you click the 'mean exposure' button in the preview, all Hugin
has to do is calculate an average of all the input Ev values to set an
optimum overall output exposure.

This is why increasing Ev for photos makes the result brighter, but
increasing it in the preview makes it darker.

Note that if your photo has accurate exposure time, ISO sensitivity
and aperture parameters, the calculated Ev value is in a 'true' scale
- In principle, a photo taken with a different camera and lens can be
exposure matched just by using these numbers.

--
Bruno