January 2012 - Digital Group - Raw Images

Meeting Notes March 2009 to 2018.
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spb
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January 2012 - Digital Group - Raw Images

Post by spb » Sat Jan 07, 2012 2:56 pm

NEWS

The Lytro Field Camera offers the intruiging prospect of retrospective decisions on focussing. Although the camera is not yet available and precise details are vague, it's certainly a technology to watch for the future.

dpReview is publishing some very interesting group reviews. Here are some that caught my eye; Mirrorless Cameras , Enthusiast Raw-Shooting Cameras , Lo-Fi Apps (ie Apps that simulate vintage film and cameras) and Portfolio Apps for the iPad which has become the device of choice for wafting your photographic portfolio around.

Kodak is reportedly preparing for bankrupcy protection. Apart from their printer business they seem to have little more than a portfolio of patents to generate income. A sorry end to the Google or Microsoft of it's day.

Camera Trace is offering a service to scour the internet for photos taken by a lost or stolen camera. It uses the EXIF data encoded in photos although whether the police would be interested in taking action to recover a stolen camera remains to be seen.

Mobile phone camera apps are the most innovative and exciting area of photography at the moment and I am convinced that all cameras will have to offer such a capability in future to compete. Two fascinating examples illustrate the level of innovation possible with the combination of technologies on a smartphone; iLightningCam which claims to be able to selectively capture lightning strikes and Pixel Blend which enables you to distress images with virtual tools on the touchscreen. I'm not saying that I necessarily want to do these things but they are novel and imaginative!

BT Infinity has come to Amersham. This will offer broadband in excess of 20Mbps and the rollout is being done street by street. One APS member on Station Rd. already has it, with excellent results. The BT Wholesale Broadband Availability Checker will give you a date for FTTC (fibre to the cabinet) for your street which is the enabling technology.

The Photography Blog has been recommended as a source of Photography news and product launches.

RAW IMAGE FILES - NB UPDATED IN THE THE JANUARY 2018 NOTES

JPG compressed image files have been dominant since the early days of digital photography and remain an excellent compromise between quality and file size. The camera settings are locked into the image at the taking stage and further processing in Photoshop negatively impacts quality.

Raw image files can be chosen in enthusiast or professional cameras and contain the image data straight from the sensor. The advantages of Raw are that decisions on exposure, colour balance, sharpness etc can be made later when the image is processed without quality loss, and the Raw file is always untouched, remaining available to re-process differently at a later date. Given sufficient skill, a Raw file has the potential to produce a superior quality image to the equivalent JPG.

Raw files come with significant disadvantages, however; each image needs individual attention, many browsers and most online sites cannot handle Raws at all, the file size is great and all previews of Raws are processed in some, often uncertain, way so they can be rather random.

The major camera manufacturers specify Raw files differently which necessitates continual, sometimes expensive, updating of software such as Photoshop. To try to overcome this Adobe have specified a universal Raw format called DNG (Digital Negative) and offer a free converter program. Many smaller camera makers output DNG straight from the camera but it has not yet caught on as a universal standard. Although conversion to DNG would remove the need to constantly update Photoshop, it does imply a two-stage process for all Raw images.

When shooting Raw, you must still pay close attention to aperture, shutter and ISO as these 'hardware' settings impact the image before the Raw is encoded and cannot be changed later. Camera settings such as Colour Space, White Balance, Saturation, Sharpness, Contrast etc are included in the Raw file but can be changed later. The preview image on the back of the camera is actually a processed JPG using all of the camera settings. It's not possible to view the actual Raw in it's native form. The processed JPG is also included in the Raw file and may be used by software as a preview - hence the rather random nature of Raw previews. A compressed, lossless Raw option on the camera may be chosen to reduce file size without any compromises.

Adobe Camera Raw (ACR) is the plug-in used by Photoshop CS, Elements and Lightroom to open and adjust Raw images and it's essential to make all big adjustments here, rather than in the subsequent editor in order to get the best quality. As a general rule, use the various sliders in the order presented to make adjustments for a particular image.

Using ACR and Photoshop Elements as an example it should not be necessary to make large Exposure adjustments if the metering in the camera is set correctly. If you find yourself consistently making the same adjustment to Exposure it would be worth considering setting a permanent compensation factor in the camera. Recovery will rescue overexposed highlights. Fill Light and Blacks will rescue shadows. Brightness and Contrast will tweak the mid-tones of the adjusted image. Clarity affects mid-tone contrast and Vibrance boosts less saturated colours. A modest amount of Sharpening should be applied here in ACR and then further appropriate sharpening added for final print or screen output.

The ACR slider settings are saved for future use with each image. Options allow them to be saved in a separate .XMP file (which requires managing) or in a common database on the computer (my personal preference). Ordinarily the image will then be opened with the Open Image button but other options are Done which saves the settings but doesn't open the image and Save Image which offers the chance to save it as a DNG. Ideally the Bit Depth setting would be set at 16 bits/channel but in Elements, most features don't work at this setting and 8 bits/channel is fine if the big adjustments have already been made in ACR.

Multiple images can be given the same settings in ACR, if the lighting conditions were consistent, to save spending time on each image individually.

My overall conclusion is that Raw is especially good at recovering shadow and highlight detail but the downsides are not insignificant. I strongly recommend that beginners stay with JPG and concentrate on learning good camera technique. Intermediates might consider the Raw + JPG option so that they can practice the skills to extract a better image from the Raw whilst having the JPG for comparison and fallback.

DATE OF NEXT MEETING

Please note that the next meeting has been moved to Wednesday 8th February.

Cheers, Steve Brabner

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