Optimize Your RAW Exposures

February 05, 2016  •  3 Comments

This week is about RAW files and optimizing exposure to give us the best possible success for post process. Think of a RAW file as a digital negative. The more information you can get on that digital negative, the better off you are in post process. The more data, the more flexibility you have to edit before quality loss.

Some photographers use JPEG. JPEG is an image compression algorithm. It takes your RAW digital negative, and using a mathematical algorithm "compresses" your file making it smaller. No mathematical formula can do this compression without image data loss. This is not acceptable to professional photographers that want every pixel from their sensor. Beware of editing JPEG files, without making a copy first, as you will again have some image loss as your editor works directly on the digital file. With RAW files, image editors actually add "what" you did in the editor to the original digital negative, thereby saving the original image data. You can see how RAW images can get even larger via post processing. This takes storage and processing resources, which is why some photographers use JPEG.

Two items can give you the best RAW file for post process, use the lowest ISO you can to eliminate noise (areas where the sensor hardware and software have to "guess" causing anomalies in the image), and, use  your histogram. What is a histogram? Think of a bell curve. The middle of the curve is a balanced image from the sensor, lights and darks. The far left is black the far right is white. Too far to the left and your image is seriously underexposed (blacks and shadows). Too far to the right and you are overexposed with blown highlights. But, no exposure will ever be a perfect bell curve. So how do you err to get the best possible outcome? Swing to the right of center. The majority of RAW "image" data from a sensor sits to the right of the histogram, therefore making it easier to adjust and not loose image quality.

We are not talking about sensor data, that remains constant. For my camera that is 12 Mega Pixels. We are talking about how much of the "image" the sensor can pick up. That gets better as the exposure improves. As sensor technology improves with newer cameras, the amount of image data at lower exposures gets better, but the concept of how much useable data in the RAW image still improves as you move across the histogram towards the right. Don't depend on the image you see in your viewfinder on the back of your camera, it does not really display the image well. Depend on the histogram, it is showing you what the image data is directly telling you.

Having a scene with shadow and bright light can cause some issues. On one side you have dark shadow, on the other you have clipped highlights. To help you decide if you are going too far to the right of center to get all that data, photographers use "blinkies" in their camera settings. If you have any blown highlights in your image, part of your rear screen "blinks" in those areas that are blown. Too much blinky, too much of your image is blown to recover on the high end. Setting your exposure to be near center or to the right of center, rather than the left, yet minimizing blown highlights gives you the best amount of data for post processing. So a mixed scene in partial shadow, partial sun, may need a few takes on exposure, adjusting aperture and shutter speed to minimize those blinkies and ISO setting.

This is what I did this week. I took my favorite cast of characters: Bonnie Border Collie, Wisp her son, with an appearance by Ginger Sorta Collie and let the fun roll. I used Bonnie's back yard which has a fair amount of shadow, with brighter light on the right side later in the day.

First, here are a selection of photos, shot in manual mode, and exposing for extremes, left and right of center, and one pretty near center. All of these photos were taken with Wisp in the same area and keeping the exposure close to ISO 500, and slight adjustments in shutter speed and/or aperture to move the histogram left or right (underexpose/overexpose). None were edited except for cropping. Wisp is a good one to experiment with, as his dark red and light white shades seriously contrast making for an interesting exposure dilemma.

Histogram far left and left of center:

    

You can see how the sensor can't get as much information. You loose image details, especially in the darker tones, even the higher tones in the grass. One could say the second photo might be nice with a little bump in the exposure to catch more of the rim light around his head... but it will not be as tack sharp, as the upcoming photos. 

Histogram as close to "bell curve" as I could get:

You can see more color data, and less shadow. His whites are brighter, you can see more grass detail. I did have a small amount of blinky around his forehead. But I could do some subtle editing to bring out detail, more so than the last two exposures.

Histogram Right of Center and Far Right:

I like the detail I see in the just right of center and know I can work more detail on his head and his eyes in post and change tones and contrast. Again I had a few blinkies around his bright white head. The final shot had all sorts of blinkies due to the blown background and you can hardly tell his whole white tail lost in the light. If your editing software has a hard time distinguishing from blown to white, you will lose edges in post.

Anyway, you can see how close to center and right of center histograms really do give good color and due to how the sensors are designed, the shots also give you more to work with. Win, Win.

Now just some fun shots, with very little editing, all at close to center or just right of center! Enjoy!

 

Wisp LOVES his Christmas present. This jolly ball is spent carrying, rolling and thumping around the back yard. He likes to put his paw on it (Mine!), stick his nose in it (I just KNOW there is another ball in there!) and carry it (look, it's a headless BC... or a red ball with a dog body and ears!)

Finally we add Bonnie and housemate Ginger into the mix along with a Frisbee. Wisp and Momma Bonnie Border Collie do this "we is both going to bring it back Mom" thing. Tonight was a bit of a first as Ginger Sorta Collie started picking up the frisbee and she and Bonnie actually started tugging with it (with Wisp on the side going... How can I get in on this action!).

Since this is a pet photography blog ring, please visit the next photographer in the ring and see her blog about this week's topic: Jodie Pholi Images Pet Photography, Ipswich Queensland.


Comments

3.Shelley Castle(non-registered)
Great pictures of them playing! Great job!
2.Jodie(non-registered)
Great Explanation , omg I laughed at the image with the big ball running towards the camera :)
1.KellyM(non-registered)
Your images are so supportive of your explanation of this week's challenge. Beautiful border collies. :O)
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