OM System OM-1 – High Dynamic Range Photography
HDR Photography Basics
The term “high dynamic range photography” refers to the process of capturing a wide dynamic range and subsequently reproducing it with a dynamic-range limited medium (e.g. print, display device).
Both tasks – capturing and reproducing high dynamic range scenes – are equally challenging.
If the dynamic range of a scene exceeds the capabilities of the digital camera, tonal values are no longer reproduced, resulting in clipped highlights and/or clipped shadows.
OM System OM-1 - clipped highlights.
Then, the scene has to be captured with multiple photographs, each using different exposure settings.
The resulting images have to be combined using either tone mapping or exposure blending.
Tone Mapping
Tone mapping is a collective term for various image processing techniques which approximate the appearance of high dynamic range scenes in a medium with limited dynamic range.
Tone mapping (flat global operator).
“Overcooked” tone mapping (local operator).
Balanced tone mapping (hybrid operator).
Exposure Blending
Exposure blending is the process of blending multiple exposures to create a high dynamic range photograph.
In digital post processing, this is usually done by layering the captured photographs. Masking or blend modes are then used to create a single photograph which represents a wide dynamic range.
Exposure blending in Affinity Photo.
In general, the greater the difference between the captured dynamic range and the reproducible dynamic range, the more difficult it is to achieve an end result that is perceived as true to life. Common problems are a loss of contrast or exceedingly artificial local tonal compression. Such images are commonly derided as having an “HDR-look”. If done properly, however, HDR photography will look natural and mimic human perception.
Exposure blending - end result.
High Dynamic Range Photography with the OM-1
1. Single Exposure HDR
Ideally, the full dynamic range of the scene can be captured with one shot. The dynamic range the OM-1 can record with a single exposure depends on the ISO setting and the photography mode (e.g. Live ND and High Res Shot increase the dynamic range).
The file format (JPEG or RAW) impacts the usability of the captured dynamic range. Theoretically, the 12-bit lossless compressed RAW can store the equivalent of 12 stops (linear).
However, all in-camera renderings are 8-bit previews based on the JPEG settings. In order to judge whether full dynamic range of a scene was captured with one exposure, the following settings are recommended:
Picture Mode: Muted.
Contrast -2.
Gradation: Auto/Shadow Adj.
By setting Gradation to Auto, the OM-1 will automatically push a great amount of dark tonal values into the final image and utilize 99% of the captured high fidelity dynamic range. The described settings are not only useful for judging the RAW dynamic range, but can also be used to capture a high dynamic range JPEG with a natural look and excellent color fidelity.
2. HDR1 and HDR2 – In-Camera Tone Mapping
With the computational modes HDR1 and HDR2, the OM-1 creates a tone mapped JPEG file in camera by combining multiple exposures.
Enable via [MENU]-[Camera2]-[1. Computational Modes]-[HDR] or map to a function button. Press and hold the function button while turning the front or rear control dial to select HDR options. Press the function button to toggle the selected HDR option on or off.
HDR quick menu (hold function button).
4-image bracketed burst. Automatic alignment and tone mapping.
Electronic shutter. 4s slow shutter speed limit.
ISO setting fixed at 200.
Picture mode: Natural. No sub-settings available.
Non-linear processing of the recorded tonal values. Black-, white- and gray points are shifted.
RAW capture is optional. When enabled, the OM-1 will store a regular, non-HDR RAW file which is underexposed by 0.5 EV.
Addendum:
Moving objects in the frame are blurred much like during a long exposure. However, if a portrait subject remains reasonably still, HDR1 and HDR2 can be used (e.g. backlit portraits).
Movement. Mode: HDR1, graded.
Backlit portrait. Mode: HDR2, graded.
HDR1 in Detail
HDR1 will give a natural result with moderately expanded dynamic range in the highlights.
Highlights: 1 stop of compression / expanded dynamic range.
Midtones: slight compression.
Shadows: insignificant compression.
In a scene with bright highlights, utilize the in-camera spot meter to evaluate either the midtones or the highlights.
Highlights: [Spot Hi], exposure compensation up to +1 EV.
Midtones: [Spot], no exposure compensation.
Shadows: [Spot Sh], no exposure compensation.
Mode: HDR1, graded.
HDR2 in Detail
HDR2 greatly expands the dynamic range in the shadows. If utilized for a low dynamic range scene or if not metered correctly, the resulting image will exhibit the undesirable “HDR-look”.
Highlights: insigsnificant compression.
Midtones: slight compression.
Shadows: 2 stops of compression / expanded dynamic range.
For a scene with very bright areas, meter to prevent highlight clipping. For other scenes meter either the midtones or shadows with the in-camera spot meter.
Shadows: [Spot Sh], exposure compensation up to -2 EV.
Midtones: [Spot], no exposure compensation.
Highlights: [Spot Hi], no exposure compensation.
Mode: HDR2, graded.
3. HDR Bracketing – For Post-Production HDR Processing
To capture a series of exposure bracketed images for tone mapping or exposure blending in post production, the OM-1 offers a set of bracketing options.
Select either via [MENU]-[CAMERA2]-[1. Computational Modes]-[HDR] or assign [HDR] to a function button. Press and hold the function button while turning the front or rear control dial to select HDR options. Press the function button to toggle the selected HDR option on or off.
When the shutter is fired, the OM-1 captures the sequence of images in one go.
Technical Details
Vibration-free electronic shutter only bracketing burst.
Bracketing step sizes: 2 or 3 EV.
File formats: JPEG and/or RAW.
No other restrictions (e.g. ISO, Picture Mode, etc.)
The shooting mode determines whether the camera either changes the f-stop (in S mode) or shutter speed (in A, P and M mode) to adjust the exposure from frame to frame.
If ISO is set to AUTO, the OM-1 can also change the ISO setting to bracket the exposures.
HDR Bracketing - Overview Table
Professional Full Dynamic Range Capture
Utilize the following method to determine the correct exposure and bracketing settings for a given scene.
1. Set a fixed f-number and ISO value.
Example: f/8 and ISO 200.
2. Meter the brightest and darkest parts of the scene with the in-camera spot meter. Note the metered shutter speeds.
Example: 1/2000 and 1/8.
3. Calculate the dynamic range of the scene based on the metered shutter speeds.
Example: From 1/2000 to 1/8 = 8 stops.
4. Calculate the required dynamic range expansion employing the following formula: [Required Dynamic Range Expansion] = [Dynamic Range] – 4.
Example: 8 – 4 = 4.
5. Select an HDR bracketing setting which will provide the required dynamic range expansion (see table above).
Example: 3f 2.0 EV = +4 stops.
6. Set the median shutter speed value. If the median cannot be set, set a slightly faster shutter speed to preserve the highlights.
Example: 1/125 is 4 stops slower than 1/2000 and 4 stops faster than 1/8.
7. Focus and capture the images.
Note:
In practice, working with full stops is more straightforward. Thanks to the high dynamic range of the OM-1, the loss of precise exposure control does not have a noticeable impact in terms of image quality when it comes to HDR composites.
Professional HDR Capture - Recommendations
Before
Do not utilize any HDR technique if the dynamic range of a scene can be captured with one exposure. The tone mapping / tonal compression will lead to an unnatural result of low fidelity.
Always evaluate the scene first.
Camera Settings
Exercise manual control over all relevant shooting settings:
Shooting mode: Manual.
ISO fixed.
White Balance: Manual.
Image Quality Setting: RAW + JPEG.
Setup
Use a tripod.
If no tripod is available, activate [Handheld Assist] and capture multiple series. Pick the sharpest / best aligned images.
Post Production
Depending on the HDR software and desired result, merging in-camera or processed JPEGs is usually preferable over merging RAW files. To name only a few advantages:
The color and tonal response are preserved so that the tone mapped image will match the look of other non-HDR images better.
Noise reduction and lens corrections will be applied.
Less computing power is required.
