Tag Archives: post

Technique

Exposure Blending – A Quick Overview

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(This is a slightly modified version of something I wrote as part of a discussion on Google+)

The author of the post that I read before writing this mentions two alternatives for dealing with dynamic range issues in landscape scenes – the use of graduated neutral density (GND) filters or the use of a similarly-named post process technique in Lightroom. (Similar processes are available in other software including Photoshop/ACR.) Another alternative is to use HDR (High Dynamic Range) techniques that allow computer algorithms to combine source images in ways that are not the same as what I describe in this post. I almost always use a different approach, exposure blending, and I’d like to share a few ideas on this topic.

When the scene contains an extremely large dynamic range – a common situation in landscape photography – it is possible to end up with shadow areas that are nearly black and devoid of detail, along with bright areas that are blown out and also completely lack detail. (The latter is especially an issue with digital capture in which overexposed areas can simply become pure white. Film failed more gracefully in this situation.)

One traditional method for dealing with such scenes is to attach various types of graduated neutral density (GND) filters to the front of the lens. These filters include a clear area and an area darkened by a few stops. A typical use might be to position the dark portion over the sky and the clear section over a darker foreground, effectively reducing the dynamic range of the light reaching the sensor by reducing only the brightness of the sky. With film, especially positive transparency film, this was just about the only realistic way to handle the situation in many cases.

A second method is to make a single exposure and use features in Photoshop/ACR, Lightroom, or other software to simulate the effect of the GND, lightening (or darkening) a portion of the photograph. This can often help quite a bit when it comes to balancing out dark and light areas in the image, and the fact is that most savvy landscape photographers do this sort of thing and more in post. But it has its limits. For example, darkening a bright area cannot put detail back in blown out areas, and lightening underexposed shadows can lead to problems with noise and posterization. The bottom line is that this technique works well when the overall range 0f brightness in the scene does not exceed the dynamic range of the camera – here it may be used to adjust the relative levels of the areas – but it does not work well when the dynamic range is actually too great for a single normal exposure.

There is a third method, sometimes called exposure blending, that can often be used when making the exposure. The idea is to make more than one exposure, with each exposure optimized for different parts of the scene by varying shutter speed, and then selectively blend the two exposures during post-production.* Two exposures are sufficient in almost all cases, with one for the shadow detail and the other for highlight detail – though in very complex or wide dynamic range situations more exposures can be used.

Continue reading Exposure Blending – A Quick Overview →
Photographs: Death Valley, Photographs: Desert, Photographs: Nature, Photographs: Southern California

Post-Sunset Glow, Amargosa Range

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Post-Sunset Glow, Amargosa Range
Post-Sunset Glow, Amargosa Range

Post-Sunset Glow, Amargosa Range. Death Valley National Park, California. March 29, 2011. © Copyright G Dan Mitchell – all rights reserved.

Post-sunset light from bright red clouds casts a reddish glow on the Amargosa Range, Death Valley Buttes, and the Kit Fox Hills.

I think this might be the second in what I could call the “impossible color” series from my late-March trip to Death Valley. (The previous image was a photograph of a wash/alluvial fan at the base of Tucki Mountain, photographed on the same evening.) The lurid and unreal colors are not the result of post-processing gone horribly wrong – the light was actually this color for a short period. The sun had already gone down behind the Cottonwood Mountains to the west of my shooting location in the middle of Death Valley not far from Stovepipe Wells. It had been an interesting sunset with the usual increase in warm colors and some attractive clouds in the sky.

What happened next was something that is probably familiar to those who have done a lot of landscape photography, though they recognize that it is not something that you can quite predict. After the sun had set and dusk was coming on, some final light from far to the west, where the sun had probably already dropped just below the horizon, began to strike high clouds above Death Valley. (I could sort of see this coming, since I had noticed increasing color in the sky further to the east.) As this happened, these clouds began to glow with an intense red color that was mixed with the normal bluish tones of dusk light and surface features took on this purple/red glow for just a brief moment before the light faded.

(Those who look very carefully may notice that the sky above and to the east of the mountains is a lot bluer than the mountains themselves. The color had already left the sky to the east, and at this point was coming from the sky directly overhead and to my west.)

I’m still trying to sort out the complex geology of this area and the ways that features are named. The larger range containing these peaks is called the Amargosa Range, though it encompasses many smaller named sub-ranges – I think these might be part of the Grapevine Mountains, roughly in the neighborhood of Thimble and Corkscrew Peaks. A dark peak in front of the main range at the very far right may be part of Death Valley Buttes, and the banded foreground hills are sometimes called the “Kit Fox Hills.”

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Commentary, History, Ideas

No Post Processing? Really?

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As I do from time to time, I’m reposting a response I shared in an online discussion somewhere else on the web. In that discussion, a proposal was made to come up with some sort of enforceable standard regarding what post-processing could be allowed in photographs. (In the context of the original discussion – wildlife photography – the idea wasn’t quite as crazy as it sounds here, but still…) It seems to me that there are always a few notions underlying these ongoing discussions: that the issue is one that comes up with “digital photography,” that there is some ideal photography that is purely and objectively “accurate,” and that we would actually want to do such a thing.

Here is what I wrote:

It seems so obvious that I’m almost embarrassed to point it out, but does anyone actually believe that there is such a thing as an objectively accurate photographic image, free of interpretation? Which acknowledged “great” photographers can you point to whose photographs are purely and objectively accurate? If digital post is a problem, what about camera movements, contraction/expansion of space via focal length, use of artificial light and reflectors, polarizing filters, graduated neutral density filters, choice of film/paper/chemicals based on color or contrast preferences, selective focus via DOF control, allowing motion blur with long shutter speeds, any night photography, and on and on…?

As I wrote somewhere else earlier this week:

If the goal of photography was to make objectively accurate reproductions of real things… I wouldn’t bother.

Have an opinion on this? Feel free to leave a comment…

 

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Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.

 

Commentary, Ideas

What is ‘Real?’

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This is another one of those posts “borrowed” from something I wrote in a discussion somewhere else on the web, in which some folks were debating the relative value of two versions of a photograph, one of which was more or less “straight from the camera,” and the other had been modified in post in a number of the usual ways. Here, with a bit of editing, is my stream of consciousness reply to that thread:

The boundaries are difficult and subjective. The “no alterations” people are denying how photography actually works with the possible (and arguable) exception of certain types of documentary and journalism photography. I know it isn’t news to most reading this, but photography is not an objectively truthful medium. In the end, I’m less interested in some hopeless attempt to literally recreate the subject than I am in what the photograph tells me about the artist behind the camera.

Specifically in landscape photography, an attempt to “reproduce” the objective reality of the original scene by eschewing “manipulation” is going to produce something in almost all cases that is not an honest or accurate recreation of the subject we saw as we made the photograph – even if that is what we were interested in. The nature of the subject and our perception of it is never wholly visual – it is bound up in a web of senses evoked by sound, the movement of air, warmth or cold, and much more. In order to somehow evoke something closer to what we felt when we saw the original subject – and that is what we are interested in, right? – we must strive for something other than a limited pseudo-true visual reproduction.

There are boundaries, but even they are not absolute. For example, many would call the classic landscape photographs more “truthful” than some of today’s color-manipulated images. But what could be less realistic than a black and white photograph? I’ve never been out on a day when it was black and white outside! On the other hand, a photographer who makes a claim to believable portrayal of the subject and then pumps up the contrast and saturates the color into Thomas Kincaid territory is going to encounter some issues about the honesty of his/her work.

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Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission fromG Dan Mitchell.