Brent Cooper
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Dodging & burning are tools invented by man to correct the mistakes that God made in tonal relationships (Ansel Adams).

Brent Cooper's conversations

Excellent view and wonderful photo. L

Thank you Wolfgang for your wonderful comment!

Thank you, your words are very kind!

L&F - Another nice one.

It’s even worse with digital cameras which have even lower dynamic range than our eyes. Typical cameras available on the market today have a dynamic range of 10 or more EVs. For instance according to DxOMark my Canon 5D MK II has a dynamic range of about 11 EVs. What do those 11 EVs really mean? Well, 2 EV is two times brighter than 1 EV, 4 EV is 2 times brighter than 2 EV and 4 times brighter than 1 EV… 11 EV is 2 times brighter than 10 EV, 4 times brighter than 9 EV, 8 times brighter than 8 EV and so on. As you can see we can turn EVs into a power of 2 and write our ratio this way: 2 ^ EV_Value : 1. In the case of my Canon DSLR it will be: 2 ^ 11 = 2048 : 1… only 2.000 : 1! 5 times worse than my own eyes! And it’s quite a powerful camera. Now think about that for a while… with typical photography we can capture only a fraction of a real-life scene’s luminosity and detail. Most of it is lost (either in shadows or highlights or both). But things get even worse… due to the design of cameras, their sensor’s data about luminosity isn’t distributed uniformly. Instead the brightest stop corresponds to 50% of all data, next stop to 25% of all data, next 12.5%… It means that 3 brightest stops corresponds to almost 90% of all data! It means that there isn’t much left for the darkest part of the regions meaning that they won’t be as detailed as highlights. So although cameras can capture 10 EVs or more there is very little information about shadows. That’s why we need to pay extra attention to properly capturing details in shadows and that is the reason for the concept of exposing the image to the right. But even when exposing to the right we won’t cover the whole dynamic range of the scene in the majority of cases. That’s when HDR comes into play. The typical image that can be displayed on a customer’s monitor has 8-bits per channel (given that typical display device can display 3 channels it results in 24-bit depth total). It means that each channel (that is red, green and blue) can have only 255 different values. Note that our monitors cannot even display 16-bit images we often work with HDR in turn is typically associated with images with 32-bits per channel. That means that a lot more data can be stored in each channel (32-bit precision allows for 4,294,967,296 different values to be stored in a single channel!) enough to represent real-life scenes in a correct way. So HDR is more an image representation than post-processing techniques that so many associate it with. HDR doesn’t have anything to do with color over-saturation, halos or other typical problems that so many users and photographers complain about. It has nothing to do with ghosting, alignment, etc. These are all imaging algorithms – nothing more. HDR is a concept of storing the image so it contains all necessary luminosity data. Both LDR (low-dynamic range – eg. typical photos) and HDR images can be thought of as models of reality but the fact is that HDR is more close to it because it can store more luminosity information than typical LDR images are capable of. That is, it can represent reality better. It doesn’t capture more information than there is present in the scene but it can capture more information than we see. It makes the statement: “HDR is unreal” false. It’s like saying that infrared photography is unreal because it shows part of the light spectrum we don’t normally see. Or that macro with scale of 2:1 is unreal because it works more like a microscope than photography… even black & white might be unreal because we see world in colours… HDR is real, it is tone-mapping that might result in unrealistic results. Now, given that I said that HDR is a model of reality it shouldn’t be surprising that contrary to what some people think HDR isn’t limited to photography. It can be used in movies, 3D graphics and also in video games – everywhere where modelling a reality is necessary.

Don't kill the messenger!

Hello, Lisa. Thank you very much, but my beard could be a lot bigger. : )

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