2011-09-11

Nikon D5100 - Auto Bracketing





Contents:
-Definition
-Using Nikon D5100 Auto Bracketing
-Visual Indicators for Auto Bracketing
-Release Modes
-Differences in Single vs Multi-frame release modes
-Using Fn (Function) to set Auto Bracketing (highly recommended)
-Picture Preview Mode (Showing +/- EV)
-When to use Auto Bracketing vs Exposure Compensation
-HDR Auto Bracketing (High Dynamic Range)
-Nikon Auto Bracket Issues and Oddities


Definition: Auto-Bracketing:

Auto-bracketing is when the camera takes 3 frames, each at a different exposure.
  • The first picture is at the metered reading (+0EV)
  • a second frame -1 stop under-exposed (-1EV)
  • a third frame +1 stop over exposed (+1EV)
The amount over and under is adjustable in 0.3 stop (EV/Exposure Value) increments.

Use this feature when you are unsure on how to set the exposure.  Common situations include strong back lighting and scenes with internal light-sources or dark shadows. Auto-Bracketing is also used with camera-based HDR.  With HDR, the three exposures are combined into one image and this can be done in-camera or with software.  However, when using HDR, I found it best to use software-based HDR (such as PaintShop Pro or PhotoShop) rather than the in-camera HDR function because you have greater control over the image.

See this Keyliner article on how to AutoBracket:
HDR Techniques for Stanley Forest Burn
NewPort Bya (Yaquina Bay Bridge)

If the in-camera HDR is used, Auto Bracketing is automatic and you cannot use the Auto Bracket feature discussed in this article - although you can adjust with width with these steps

Common Error:

If the camera displays an HDR error when Auto-Bracketing: "This option is not available at the current setting or in the camera's current state", see this article: Turning off Auto-Bracketing for HDR (plus other conditions that can trigger this error) plus see this article for other details on bracketing.

For a small run of exposures, Auto Bracketing may be more trouble than it is worth and you might consider using manual +/- Exposure Compensation.  Reasons to chose auto bracketing over exposure compensation are explained later in this article.


Using Nikon D5100 Auto Bracketing:

Setting Auto Bracket Style:

Auto Bracketing is controlled in two different menus.  As a one-time event, set the Auto Bracket 'style' -- where I recommend "exposure only" -- then separately, set the bracketing amount for the current round of photos.

1.  Set Auto Bracket Style

Start by setting what type of Auto Bracketing you want to use.

Three styles are supported
  • AE (Auto Exposure Bracketing - recommended)
  • WB (White Balance Bracketing)
  • ADL (Active D Lighting bracketing (on-off)

This is a one-time setup and I recommend choosing Auto Exposure (only).

From the manual:  Nikon supports multiple types of bracketing. This article is concerned with Auto Exposure Bracketing.

Illustration from Nikon D5100 User's Manual.  Click for larger view; click back to return.
Note the upstairs window exposures.  At +0EV, and +1EV, the window's highlighted details are blown-out.

Setting Auto-Bracket Style:

A. Press "Menu" / Pencil
B. Select "e" (Bracketing/flash)
C. "e2" Auto Bracketing set
D. Select "AE" (Auto Exposure bracketing "OK")
E. Press "Menu" twice to return to normal exposure mode







2.  Using Auto Bracketing while Shooting



After setting the style, turn Auto-Bracket on with these steps. Once turned on, the camera will auto-bracket all photos in groups of 3 until turned off.  Only groups of three are supported.




A.  Press "i" to activate the Information Display. 

The Information Display may be set to show a simple or more complicated screen; both are illustrated.

B.  Press "i" a second time to position the cursor along the right side.

C.  Setting the Width or Spread:

- Arrow-key down to the BKT section (illustrated in yellow, above).
- Click OK to select the bracketing option - e.g. "stops".

Typically, choosing AE07 or AE10 (1 stop).


(See below for a faster way to make these adjustments)



3.  Take the pictures

Compared to other camera brands, the D5100 does not Auto Bracket as most would expect and the owner's manual does not fully explain the feature; many think the camera is in error.  When Auto Bracketing, you must manually fire the shutter 3 times.


Once the bracketing width is set (AE0.7, AE1.0, etc.), press the shutter 3 times, firing three separate exposures. 
  • The first will be taken at the camera's indicated meter reading.  
  • The second will be one stop (AE-1.0) under exposed (or as set) and 
  • The third will be one stop (AE+1.0) over exposed (or as set). 

Caution
When Auto Bracketing is turned on, it remains on.  
All subsequent photos are shot in groups of 3 (+0EV, -1EV, +1EV).  You must complete the sequence by manually pressing the shutter 3 times.



Quickly Setting Auto Bracketing with the Fn button:

The Nikon 5100 has a user-assignable Fn button, which can be assigned to any function.  Because HDR is becoming so common, I like to assign Fn to Auto Bracketing. By pressing Fn and spinning the dial, I can adjust the bracketing width on-the-fly, from 0 to 3 stops.  This is faster than either the "i" or regular menu.

Follow these one-time steps to program the Fn button:

A.  Press MENU
B.  Open the Controls Menu (the Pencil)
C.  Choose f1 "Assign timer/Fn button"
D.  Select Bracketing (last item in the scroll list)
E.  Press MENU, MENU to return


Using the Fn button:

1.  Press and hold Fn
2.  Spin the thumb-wheel to set the spread (+/- EV)

Set to 0 to turn off Bracketing



Visual Indicators for Auto Bracketing:

With Auto Bracketing ON, there are several subtle indicators.

* In the View Finder, note the "BKT" indicator near the ISO setting.  Note: This does not show you which exposure you are at, nor does it show if you are in the middle of a series.










* The LCD Panel shows "BKT" in the lower-right corner. 
Illustrated, "BKT Off" or BKT AE0.7, etc.













* The LCD panel shows an Exposure Compensation bar-graph, telling you which exposure in the series you are on. 

The graph shows 3 markers at the beginning of the sequence; each marker represents where the next photo will be taken.  In the illustration, the center marker is at "0".  Marker 2 is at -AE0.7 (EV -0.7 stops) and marker 3 is at +AE0.7.  Widths are adjustable.

The markers show the remaining exposures and they disappear as each photo is taken.  The second-half of the illustration shows one exposure remaining of the original three.


Note how the Information Display shows the horizontal graph, but the internal View Finder does not show +/- Exposure Compensation is active (this is inconsistent with the normal +/- functionality).







Release Modes

The three line segments, illustrated above, indicate 3 exposures are remaining in the sequence, and in this case, each exposure is 0.7EV units  (2/3's of a stop).  The width is adjustable.

Each time the shutter fires, one less segment displays. 
The first exposure is always at "0",
the second is at "-1" (or at your set interval), and
the third is at "+1". 

If the camera's Shutter Release Mode is set to "Single", you will need to manually press the shutter 3 times. (Contrast this with other brands of cameras: Pentax fires three shots automatically with one shutter press.)

If the Shutter Release Mode is set to "Continuous," press and hold the shutter and all three shots fire in sequence.  At the third shot, the shutter quits firing.  Re-press the shutter to start a new 3-shot sequence.  Note: In Continuous mode, it is possible to lightly press the shutter and only fire one or two shots -- it does not automatically fire all three shots.  If in this mode, press and hold the shutter until the sequence is complete.

I recommend using the Single release mode and pressing the shutter three times.


Stopping a Mid-stream Auto Bracket Sequence:

To stop an Auto Bracket in mid-sequence, do one of the following:
A.  Press Info to enter the Video Information Panel
B.  Scroll to the lower-right "BKT" menu; set to Off

If using the Fn menu, described above, follow this alternate path:
A.  Press and hold Fn
B.  Spin the thumbwheel to zero (0)



Picture Preview Mode:

Once the exposures are taken, you can see which frames have exposure compensation (aka Auto Bracketing).  Click the Preview button, then Up-Arrow to view the picture's statistics.  Note the +/- Exposure area, illustrated below.  The first frame is taken at the metered reading and displays as blank (+0).  The next frame is -1, the third frame is +1 (or at the increment set).



Auto Bracket vs Exposure Compensation:

Discounting the special needs of HDR, in practice most photographers know which way they want to bracket (over exposing or under exposing).  As you will see, auto-bracketing wastes a frame by going in the wrong direction for one of the three photos.  If you are unsure of your exposure, the "Exposure Compensation" control may be a better feature to use.  Examples are described below.

When to use Auto Bracketing vs a simpler +/- Exposure Compensation comes with some experience.  

Photo: Nancy A. Henry
Consider Auto Bracketing when the light source is in the photo and you are unsure whether to capture shadow or highlight details. 

For example, with sun-beams streaming through the trees, the camera will likely meter the scene incorrectly -- and a correct meter reading is up for interpretation.  If over-exposed (from the meter's point of view), shadow-details will be better.  If under-exposed, the shadows may be more interesting and ominous and more details would be visible in the sunlight.  It could go either way.

Auto Bracketing is somewhat pointless if the subject against a bright window (strong backlighting) or against a bright (snowy) background.  Because you are after foreground detail (the person standing against the window/snow).  Use a simpler +/- Exposure Compensation and over-expose by +1.5 or +2 stops.  The -1.0 auto-bracketed exposure will be a wasted frame, with even darker shadows, and you would have been better served by multiple exposures in the other (+) direction.

Colorful sunsets may benefit from Auto Bracketing, but likely, the over-exposed frame will be wasted.  In this instance, using +/- Exposure Compensation and under exposing by -0.5, -1.0 or -1.5 emphasizes the colors while deepening the shadows, giving a more dramatic effect.


HDR
High Dynamic Range photographs (HDR) are different and they must have three (or more) bracketed exposures to work properly.  In some photographs, especially landscapes, where there are large contrasts between the highlights and shadows, the camera or software can blend the three images into one properly exposed photograph.  See this article:  HDR Photo Techniques.

A decision needs to be made.  If you intend on using your computer photo editor to build the HDR, then you must shoot (three) bracketed exposures, using either the bracketing discussed here or using manual exposure compensation.  If you are using the camera's built-in HDR function (using only the camera and not a computer), then the HDR function automatically brackets with no action on your part, except to set the bracket width.

Because Nikon's Auto-Bracket is limited to 3 frames, I seldom use Auto-Bracketing and instead choose to manually set Exposure Compensation and I shoot 5 exposures at +2, +1, 0, -1 and -2.  Then using software (Paintshop Pro, Photoshop, etc.,), I build the HDR manually, with better results than the camera.  See related articles, below, for details.


Nikon Auto Bracket Issues:
With Auto Bracketing turned on, be aware of these important issues:
  • For normally contrasted scenes, those with normal highlights and shadows, I like to set the camera's auto-bracketing range at +/- 0.7 stops  (2/3rds of a stop, either direction).

    For night-shots, such as cityscapes, with a mixture of deep, dark blacks and bright street and building lights, consider +/- 1.0 or 1.3 stops.  This gives you more to play with when using HDR but can result in a stylized photograph.

  • The frames/exposures do not "auto-advance."  You must fire the shutter 3 times for all 3 bracketed exposures.
     
  • The camera shutter behaves differently, depending on the "Release Mode" (Single-frame or Continuous).  If you are in "Single" mode, manually fire the shutter 3 times to advance through the sequence.  If in "Continuous," press and hold the shutter until all three frames are taken - the camera will automatically stop at the third exposure.
  • Auto Bracket does not "reset" when the camera is turned off -- you must take the three frames or manually turn off Bracketing.  The camera does not forget the bracketing sequence, even if you turn the camera off or change other exposure settings. 

    For example, you take 2 of the 3 shots, turn the camera off and go home.  The next day, you take a photo at the birthday party, and that shot will be the third in the auto-bracket sequence.
     
  • The View Finder does not show where in the 3-frame sequence you are, however, there is an "Bkt" indicator.  The View Finder does not show the exposure compensation of the current bracket.
     
  • If Auto-Bracketing is on, you cannot select the camera's built-in HDR mode: "This option is not available at the current settings or in the camera's current state."   To resolve this issue, set the Auto-Bracketing AE to zero.
     
  • If you are using the in-camera HDR, Auto-Bracketing is automatic, including advancing the frames; you do not fire the three frames.  The camera will assemble all three frames, combining them into one final image.  However, software-based HDR (PaintShop Pro, Photoshop, etc.), will give better HDR results.

Related articles:
White Balancing
Using an 18% Grey Card
 

HDR Techniques for Stanley Forest Burn
NewPort Bya (Yaquina Bay Bridge)
Highway 21 HDR


Post a Comment