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Zaffa

Zaffa

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When I use my D7100's inbuilt automatic exposure bracketing in Manual or Aperture Priority , why is it altering my EV range AND my Shutter speed together ? Seems to defeat the whole purpose of getting a sequence of photos from light to dark .

My camera seems to be fighting my every attempt to get the range from darker to lighter photos to complete an EV series to combine them in Photomatrix for HDR purposes . My metering mode is on spot .

When I look at the properties of each photo on my computer afterwards , I notice that the shutter speed is changing with each EV step change. I have the ISO and F-Stop locked in to be the same for the series of EV shots . The only parameter I want to change is the EV , or even better , only the Shutter speed . But it seems the EV is linked to the Shutter Speed and vice versa . Im wondering if my metering mode or some other simple option needs changing to rectify this ?

If someone could help me with this I would greatly appreciate it .
 
Zaffa said:
The only parameter I want to change is the EV , or even better , only the Shutter speed .
Click to expand...
If you're in aperture priority and you set up bracketing with a fixed ISO value then shutter speed should change.

I don't know what you think EV range is, but the only way the the camera can make a brighter or darker exposure in this way is to adjust shutter speed.
 
The whole point of bracketing exposure is to take one (or more) photos darker than your assumed correct exposure (ev -) and one (or more) brighter than your assumed correct exposure (ev +).

If the aperture and ISO remain constant, the only other way to accomplish this is the modify the shutter speed.

And this would be generally exactly what you would do for most HDR techniques.
 
Seems that I am the idiot in this equation ! ....So E.V and Shutter speed are one and the same thing ? I thought they were seperate ..doh

Im on a steep learning curve at present. Only just started using manual a couple of weeks ago on a new camera , my first Nikon . Previously only ever shot in auto on my sony nex5n
--
The goal of software engineers it to make bigger, better, idiot proof software.
The goal of the Universe is to make bigger, better idiots.
Apparently the universe is winning this race .
 
There are three variables that alter exposure: shutter speed, aperture and ISO. The EV (exposure value) you see in the camera doesn't change the exposure itself; by using the exposure compensation feature, one of the three is altered automatically to create an image that's brighter or darker than what the meter reading says is "correct exposure".

In Manual mode, the exposure compensation feature is not present. That's because the camera doesn't control anything automatically. So to brighten the image by 1 EV (1 exposure value, 1 stop, etc.), you need to change either the shutter speed, aperture or the ISO.

Changing the aperture is not sensible at all. This directly controls the depth of field, so by changing the aperture between shots you risk getting out of focus shots that will be blended together with shots that are in-focus, and that will be a mess.

If you're using a tripod, and the photographed subject isn't moving, there's really no reason to change the ISO. Just set it to base ISO, and change the shutter speed.

Here's a nice technique I found, that I now use all the time: Creating The Realistic HDR Image
 
There are only 3 ways to control light in-camera.

Aperture
Shutter speed
ISO

Beyond that, you need ND filters or other external influences.

In your case, something has to change to give you different ev exposures. Shutter speed is probably the best option as you'd want the ISO and DoF to remain identical.
Had you wanted to capture moving water and bracket, your best option would be ISO for in-camera, or ND filters so that everything could remain the same.
I've never done it this way though. Is it generally discouraged to change ISO in a bracketed set? Out can you go back in pp and add some grain to the lower ISO images?
 
Ido S said:
Ido Scharf said:
Ido S said:
There are three variables that alter exposure: shutter speed, aperture and ISO.
Click to expand...
please dont spread this piece of misinformation.
Click to expand...
Perhaps you can shed some light on the issue? (No pun intended.)
Click to expand...
He's using the equivalence theory's definition of the word.

Never mind that fact that if you need ISO 3200, and use ISO 100 by mistake, you'll screw up your shot. That doesn't matter. :D
 
Martin.au said:
He's using the equivalence theory's definition of the word.
Click to expand...
That doesn't mean that exposure isn't controlled by shutter speed, aperture and ISO, so I'm still puzzled as to what he actually wants.
Martin.au said:
Never mind that fact that if you need ISO 3200, and use ISO 100 by mistake, you'll screw up your shot. That doesn't matter. :D
Click to expand...
In order for the equivalence theory to work, you need lenses that are comparable with crop factor, too. So let's say you're using a full frame camera at 1/500 sec., ISO 3200 and the lens at f/4, a Micro Four Thirds setup will match this with 1/500 sec., ISO 800 and f/2. This will give the same exposure (-2 stops in ISO +2 stops in aperture = 0), with the same depth of field (assuming the focal lengths used correlate with the crop factor) and same amount of noise overall.
 
Ido S said:
Ido Scharf said:
Ido S said:
There are three variables that alter exposure: shutter speed, aperture and ISO.
Click to expand...
please dont spread this piece of misinformation.
Click to expand...
Perhaps you can shed some light on the issue? (No pun intended.)
Click to expand...
"Exposure" has quite a few meanings in photography. These include (among several others):
  1. Exposing a sensitive medium to light.
  2. The result of that exposure (a picture or photograph).
  3. The appearance of the photograph.
  4. The settings needed to obtain that appearance.
Those meanings obtained their meaning by general usage. That's the way most words in everyday use get their meanings.

At the end of the 19th century, as the basic materials and techniques of photography became stabilised, some people worked out how to assess the settings (meaning 4) needed to obtain a given appearance (meaning 3).

At that time the sensitive medium could be made with a various sensitivities but each individual piece had a particular sensitivity. As a result, the settings that could be altered to change the appearance (exposure) were twofold: aperture and shutter speed. A photographic manual was published, which defined "exposure" (or, as it is sometimes more usefully called, "photometric exposure") as the combined effect of aperture and shutter speed.

That definition was useful then and remains useful today (in-camera exposure metering and settings depend on it). It never was the only photographic meaning of "exposure" but some people think it was (and is). Note that this particular meaning was obtained not by general usage but by definition. That's a normal, natural occurrence; but giving a word a defined meaning in one context can never override any other meanings it has.

Photography is nothing if not practical; a two-term definition of "exposure" was fine if there were only two things that could change. But with digital photography we can alter the effective sensitivity (see below) or ISO, so that adds a third variable and the two-term definition need no longer rule.

But some people think it should. They resist the perfectly sensible, pragmatic inclusion of ISO in digital exposure ... which is why your statement is called "misinformation".

Effective sensitivity. A digital sensor has a fixed sensitivity, so we can't actually alter the sensitivity of the medium. Changing ISO actually alters the gain (electronic amplification) applied to the digital signal after it is captured. In raw, increasing ISO (gain) doesn't actually achieve very much, so to that extent the old definition is fine. However, in JPG shooting the effective ISO is frozen as soon as the in-camera conversion is made, so the effect is real: that's why I said "effective sensitivity"/

Even with cameras that can deliver raw output, the majority of users probably shoot JPG. The exposure triangle - your three-variable system - is therefore perfectly valid; and I see no point in having one definition for raw shooters and one for JPG shooters.
 
Martin.au said:
Ido S said:
Martin.au said:
Ido S said:
There are three variables that alter exposure: shutter speed, aperture and ISO.
Click to expand...
please dont spread this piece of misinformation.
Click to expand...
Perhaps you can shed some light on the issue? (No pun intended.)
Click to expand...
He's using the equivalence theory's definition of the word.

Never mind that fact that if you need ISO 3200, and use ISO 100 by mistake, you'll screw up your shot. That doesn't matter. :D
Click to expand...
equivalence has nothing to do with this.
 
Ido S said:
Ido Scharf said:
Ido S said:
There are three variables that alter exposure: shutter speed, aperture and ISO.
Click to expand...
please dont spread this piece of misinformation.
Click to expand...
Perhaps you can shed some light on the issue? (No pun intended.)
Click to expand...
exposure only refers to to how much light is exposed to the sensor. Within the camera only two parameters cam affect this: Aperture opening and Shutter open time (which has also been given a misleading name of shutter speed).

ISO plays no part in this, in fact it does not even change sensitivity of the sensor as it has often been misrepresented. All that ISO setting does is changing the brightness of the final image and it does so by either hardware amplification/gain or software brightening. But it is true that in-camera metering system takes ISO setting into account when calculating exposure value, thus leading the mistakened belief that ISO is part of exposure.

Let me give you an example. If you shoot a static portrait in daylight where it is possible to shoot at f2.0 1/500s ISO 100, if you took this shot at F2.0 1/8000 ISO1600, then you will get a equally bright, but severely underexposed image.
 
Ido Scharf said:
There are three variables that alter exposure: shutter speed, aperture and ISO. The EV (exposure value) you see in the camera doesn't change the exposure itself; by using the exposure compensation feature, one of the three is altered automatically to create an image that's brighter or darker than what the meter reading says is "correct exposure".

In Manual mode, the exposure compensation feature is not present. That's because the camera doesn't control anything automatically. So to brighten the image by 1 EV (1 exposure value, 1 stop, etc.), you need to change either the shutter speed, aperture or the ISO.

Changing the aperture is not sensible at all. This directly controls the depth of field, so by changing the aperture between shots you risk getting out of focus shots that will be blended together with shots that are in-focus, and that will be a mess.

If you're using a tripod, and the photographed subject isn't moving, there's really no reason to change the ISO. Just set it to base ISO, and change the shutter speed.

Here's a nice technique I found, that I now use all the time: Creating The Realistic HDR Image
Click to expand...
Thank you for going to the trouble to explain that and for the link . I seem to have a habit of throwing myself into the deep end , learning manual and hdr at the same time , hdr is helping me understand my camera better .
 
PalmettoFellow said:
There are only 3 ways to control light in-camera.

Aperture
Shutter speed
ISO

Beyond that, you need ND filters or other external influences.

In your case, something has to change to give you different ev exposures. Shutter speed is probably the best option as you'd want the ISO and DoF to remain identical.
Had you wanted to capture moving water and bracket, your best option would be ISO for in-camera, or ND filters so that everything could remain the same.
I've never done it this way though. Is it generally discouraged to change ISO in a bracketed set? Out can you go back in pp and add some grain to the lower ISO images?
Click to expand...
All the articles ive read have stated that changing iso in a bracketed exposure series for hdr purposes is not the way to do it as the higher the iso the less dynic range , defeating the whole purpose .
--
The goal of software engineers it to make bigger, better, idiot proof software.
The goal of the Universe is to make bigger, better idiots.
Apparently the universe is winning this race .
 
Zaffa said:
Seems that I am the idiot in this equation ! ....So E.V and Shutter speed are one and the same thing ? I thought they were seperate ..doh
Click to expand...
Not really...

Let's ignore the nitpickers who say ISO isn't part of "exposure", and throw it in simply because we use it all the time.

The shutter speed you set is 1/100 sec., the aperture is f/16, and the ISO is 100. This combination gives a "correct" exposure in broad daylight, according to the tried and true Sunny 16 rule.

You changed the shutter speed by 1 stop, and it's now 1/50 sec., without changing aperture and ISO. The exposure you get, is +1 EV compared to the previous one. Go the other way, to 1/200 sec., and it's -1 EV.

Change the aperture without changing the other two settings. From f/16 to f/11, you get +1 EV. from f/16 to f/22, that's -1 EV.

Change the ISO without changing the other two settings. From 100 to 200, that's +1 EV. If there were ISO 50 in modern-day DSLRs, changing to it would give -1 EV.

To balance it out and give a "correct" exposure again, you need to alter a different setting.

That's as simplified an explanation as I was able to provide. Hope it's understandable.
 
Ido S said:
Zaffa said:
Seems that I am the idiot in this equation ! ....So E.V and Shutter speed are one and the same thing ? I thought they were seperate ..doh
Click to expand...
Not really...

Let's ignore the nitpickers who say ISO isn't part of "exposure", and throw it in simply because we use it all the time.
Click to expand...
I am not being nitpicking, and it is being used all the time doesnt mean it is not wrong.
Ido Scharf said:
The shutter speed you set is 1/100 sec., the aperture is f/16, and the ISO is 100. This combination gives a "correct" exposure in broad daylight, according to the tried and true Sunny 16 rule.
Click to expand...
Lets use your sunny day example, do you think 1/800, F16, ISO 800 yield correct exposure?
 
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