FastRawViewer Developers' Blog

Dealing with Damaged RAW Files

FastRawViewer. Damaged shot. RAW. Zoom to 24%

"I should have checked all the frames before I left the site!

There does seem to be a problem with the green channel but with the tools I have I can't get my head around it. Looks like I will have to contact Canon."

You may find this article to be useful in a practical way, not just as an isolated case of raw data damage. Often, just a casual look into raw data provides arguments allowing one to persuade technical support that there is a problem with your camera body that needs to be addressed.

Deriving Hidden Baseline Exposure Compensation Applied by a Raw Converter

ACR Process 2010 Default Settings

We explained in an earlier article (“Forcing a Raw Converter to Render Tones Accurately”) that the majority of raw converters process raw shots with hidden, uncontrolled adjustments. This can cause a bumped midtone, clipped highlights, and compressed shadows; ostensibly, the point of this is to "improve" the way the shot looks.

Here, we intend to show you how to determine what sort of unseen exposure correction is being applied to your raw shots by your raw converter.

Forcing a Raw Converter to Render Tones Accurately

"What happens to my mid-tones? I set exposure using exposure meter; open the shot in Adobe Lr (or Adobe Camera Raw, or some other converter) - the shot looks overexposed and everything starting from mid-tone and up looks very flat. If I shoot RAW+JPEG, JPEG looks OK, while RAW is not. Should I expose lower?"

Df_CT02.NEF in ACR - image looks overexposed and flat on the higher tones

Don't set the exposure any lower. You'll have underexposed by another stop in addition to the underexposure caused by camera meter calibration. This can be painful, particularly if you don't have a lot of light and have already cranked up ISO to above 400.

We'd recommend fine-tuning the default settings that your raw converter has (detailed below). Taking the time to set up customized defaults now will save you a lot more time later.

Is it Worth it to Cull with a RAW Converter?

Import all images

Can one find tricks and tips on the most bearable way to use John Deer tractor for preparing flowerbeds in one's small backyard? Probably yes, and probably a lot of them. But is it worth to use Jonh Deer for this task at all? Definitely, not. Same situation is with culling with a RAW converter.

RAW converters are not designed for culling. Instead, RAW converters are supposed to work with a relatively small number of "keepers," which have already been chosen for conversion and further processing.

The main purpose, and therefore the modus operandi, of any RAW converter is to render the best possible conversion of a RAW file to some image presentation format, and not deal with a plentitude of RAW images while culling.

So the best trick here to simplify and speed up your culling procedure is to use an application that is designed to be a culling tool for RAW shots.

Why Bother Shooting RAW if Culling JPEGs

FastRawViewer. Culling RAW vs Culling JPEGs

What do you think is the possibility, when you are choosing and sorting images based on the JPEG previews, that you are going to discard the better-quality image, and keep the lesser-quality one?

When culling shots judging the technical quality based on the embedded JPEGs or uncontrolled RAW conversions instead of RAW, you risk making a mistake, especially with difficult scenes having deep shadows, throwing away perfectly good exposures in favor of the not-so-good – because, in some sense, you are choosing the shots while mislead or even blindfolded.

Let’s take a look at a typical “training” shot for a holiday – noon of a sunny day, blue Ionian sea, bright white limestone pebbles, bushes with dark-green, high-detail leaves (which lose all detail if the shot is underexposed), deep shadows under the bushes. These types of scenes typically have a very wide dynamic range. We will see later, however, that the real range of the shot we are examining is pretty much only 8 EV, if the exposure is technically correct.

Dispelling a Myth: Viewing RAW is Impossible

"There is not much sense in RAW viewers - one can't view "RAW images" anyway because RAW is not an image at all".

Yes, how often do we hear this myth: RAW is not an image. This particular misconception is extremely convenient and is often used as an excuse by those trying to explain why it is only natural that most image viewers display embedded JPEG instead of RAW, JPEG-based histogram instead of RAW histogram, and over- and underexposure indicators derived from JPEG previews.

The culprit here is that a JPEG is considered to be instantly viewable, because it contains a "processed image", while a RAW needs conversion ("development"), as it is a "latent image".

In fact, RAW is an image, but in a less familiar format.


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