Raw vs JPEG and Sharpening

Category: Education

Presentation Description

A presentation I g ave to Ringwood Camera club explaining RAW and JPEG files plus a look at Sharpening


Presentation Transcript

RAW vs JPEG plus Sharpening Explained:

RAW vs JPEG plus Sharpening Explained Mike Richards


Introduction Second talk to help you better utilise the special features of digital cameras Noise and ISO last time RAW vs JPEG and image sharpening this time Features under-utilised due to lack of understanding – playing-safe So , let’s start with RAW vs JPEG and a look at the sensor But first ………

Can you believe your eyes?:

Can you believe your eyes? Not really! Our eyes and brain work together to create a version of reality In bright light colours are detected by three different size of cones on the retina. Cone sensitivity roughly correspond to Red, Green and Blue The brain analyses these signals to give a perception of colour We are easily fooled!

The Digital Camera Sensor:

The Digital C amera S ensor


Sensor quality 0 255 0 0 Compact camera 8-bit sensor Older SLR or Bridge camera 12-bit sensor 4,095 Modern SLR/MFT 14-bit sensor 16,383

The Sensor:

The Sensor B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G B R G Pixel 4 thousand pixels 3 thousand pixels 12 megapixels sensor


Real Sensor Pixel Beyer Array

Bayer Array:

Bayer Array De-mosaic the array Emulates the human brain technique for creating colour Calculate the colour of each pixel Measures the Red, Green and Blue light Uses two Green sensors per pixel to simulate our eye’s greater sensitivity t o green light Colour for each pixel is calculated using data from the surrounding pixels – same as in the eye/brain Estimate the white balance Attempts to compensates for the colour of the light Output is corrected Red, Green and Blue values

Processing the Sensor Information:

Processing the Sensor Information De-mosaic and white balance Red Green Blue Green Sensor Tone curves a nd JPEG conversion Red Green Blue Final JPEG image RAW file Bypasses in-camera processing

In-Camera Processing:

In-Camera Processing All digital cameras contain a small computer Manages the settings Operates the shutter, aperture, etc. Interprets the data from the sensor Creates a JPEG image to show on the rear screen JPEG image is used for the histogram Saves the image to the storage card

Understanding JPEG files:

Understanding JPEG files File format is designed specifically for photos Keeps brightness info but discards some colour info Reduces file size by 10 times or more Saved file is 8-bit (256 values) so you lose some sensor information Also, every time you save you lose quality – it’s lossy Camera info and date embedded in EXIF


JPEG & RAW What about sensors with more than 8-bits? 14 bit sensor 8-bit JPEG We have to convert to 8-bit sometime Screens are 8-bit Printers are 8-bit Disadvantage: Camera decides what to discard! 0 16,383 0 255 Squished!

JPEG – How do they do that?:

JPEG – How do they do that? 8 pixels 8 pixels Original = 192 bytes Red = 185 Green = 205 Blue = 229 Red = 187 Green = 197 Blue = 227 Red = 220 Green = 230 Blue = 242 R186 – G201 - B228

JPEG Artefacts:

JPEG Artefacts Original JPEG After 25 saves

RAW vs JPEG Examples:

RAW vs JPEG Examples


Unprocessed JPEG Processed JPEG Processed RAW HD Multiple Exposure RAW


Unprocessed JPEG Original JPEG - Unprocessed JPEG Processed In Camera Raw RAW Image processed in Camera Raw


Unprocessed JPEG Original JPEG JPEG Processed Raw Processed

JPEG vs RAW – Pros & Cons:

JPEG vs RAW – Pros & Cons JPEG Pros JPEG Cons Small file size You lose sensor information Ready to use – no need to process White balanced fixed Better for high-speed shooting Sharpening already applied RAW Pros RAW Cons Captures all the sensor info Larger files White balance can be changed Has to be processed in computer Better h ighlights & shadow r ecovery High-speed shooting can be restricted Full control of sharpening

JPEG Shooting Tips:

JPEG Shooting Tips Use good photographic technique Fill the frame with the subject Choose your viewpoint to simplify the subject Check the histogram for good exposure Use Scene modes* Set the white balance for unusual lighting* Editing Avoid repeated saving of JPEG files

RAW Shooting Tips:

RAW Shooting Tips Get to know your camera Take some photos with the histogram pushed to the right to see how much you can recover Most cameras can shoot RAW & JPEG simultaneously Handy for quick sharing

Tools for improving photos:

Tools for improving photos A good starting point: Exposure You often need to brighten-up RAW files, start by increasing Exposure Black point After adjusting exposure, extending the black point puts some punch back Shadows Adjust to improve detail in darker areas Highlights and Whites Use to control very light areas



How do we sharpen:

How do we sharpen Increase contrast at the edges of details Make the dark areas darker and the lights lighter If overdone will cause sharpening halos to appear Doesn’t help with photos that are out of focus! Here’s an example…


Rose before sharpening Rose sharpened Rose zoom unsharpened Rose zoom sharpened


Sharpening Three types of sharpening: Capture sharpening Creative sharpening Output sharpening


Capture sharpening Most digital cameras deliberately blur the image! Need to diffuse light across the Red Green and Blue buckets to avoid moire ….

Capture sharpening:

Light Sensor Pixels Light Aliasing l ow-pass filter Capture sharpening

Another look at the sensor:

Another look at the sensor Sensor Low pass filter and micro-lenses Photons

Capture sharpening:

Capture sharpening When shooting in JPEG Capture & output sharpening applied automatically You may find a sharpening adjustment in settings When shooting in RAW Capture sharpening applied automatically in manufacturer’s own RAW software Lightroom and Camera Raw use pre-sets that you can adjust Tips Adjust with caution Only fine correction required at this stage

Creative sharpening:

Creative sharpening Use sharpening and blur effects to enhance photos P ortrait Provide extra sharpening to the eyes Soften the face Landscape Sharpen tree outlines and focal points Soften the sky or sea Here’s an example ….


Capture only Creative sharpen Creative sharpen 2

Output Sharpening:

Output Sharpening Optimise image for the type of display…. Computer screen and Internet Inkjet print – dot gain Other print medium Should be done after re-sizing the image Check carefully for halos or other odd effects


RAW from camera, no sharpening Capture sharpening applied Output sharpening applied

Sharpening methods:

Sharpening methods Unsharp Mask Photoshop CC Photoshop Elements – Enhance menu Controls the amount of sharpening Sets the detail to sharpen (0.5 to 0.9 pixels) Use this to prevent sharpening of flat tone a reas such as skies

Sharpening methods:

Sharpening methods High pass filter Flatten your image or take a stamp ( Ctl + Alt + Shift E) Create a duplicate Select filters – Other High Pass and set pixels to 3.6 When complete, change the blend mode of the low pass layer to hard light or soft light Adjust the sharpening effect by changing the opacity of the high pass layer.

Sharpening methods:

Sharpening methods Pixel Genius Expert Photoshop actions Handles capture, creative and output sharpening Applies sharpening as layers – can be adjusted with opacity


Capture sharpening only Modest unsharp mask Over sharpened Pixel Genius sharpening

Sharpening dangers:

Sharpening dangers Oversharpening Creates a halo around high contrast areas Creates a gritty, sketch-like appearance


Summary RAW files useful facility Access to highest quality images JPEG surprisingly good Make use of scene mode and white balance for best results Sharpening Choose your method Unsharp mask High pass filter Pixel Genius, etc.