Can Dynamic Range Be tested?

[martcol]

I find getting correct exposure probably the most frustrating thing about using my 10D. There, I said it.

Sometimes I wonder if there's something wrong with the CMOS because no matter what, I usually find some element of the shot blown out or, if not, shadow detail is really dark. So, am I expecting too much from the camera or am I missing something? Can I test a shot I mean the thing I point the camera at, to see what the dynamic range is? How do you know? Are there limits to what you can expose comfortably, barring the obivious sun behind stuff? If there are limits are they the same from camera to camera (10D to 10D)? A typical example for me is a shot with a reasonable amount of sky in it (in the UK). Invariably I get lovely exposure on the ground and a blown out sky or visa versa but never lovely exposure on both.

I am ploughing through this thread: http://photography-on-the.net/forum/showthread.php?t=25240&highlight=dynamic+range

and this link: http://www.luminous-landscape.com/tutorials/expose-right.shtml
and they are useful but.... I still don't understand.

Am I the only one? Should I really have stuck with stamp collecting? :roll:

Martin

[maderito]

The threads you're reading are about "shooting to the right" which attempts to minimize image degradation in shots that do NOT use the full dynamic range of the CMOS sensor.

For outdoor shots with sky, you could start by looking up threads on polarizers (or circular polarizers) and graduated neutral density filters.

There are other tricks to capturing a scene with a dyanmic range that exceeds your camera's capabilities (including the old standby - go back to color negative film :) ). At a minimum, you need to shoot in RAW. I'll leave it to others to comment/suggest further.

[chris.bailey]

A couple of thoughts.

* As Woody says, shoot in RAW

* Not all pictures will cover the full dynamic range. Dont expect the histogram to be the shape many articles suggest you to be aiming for.

* Process from RAW into AdobeRGB (C1, Breezebrowser or CS all do much the same as far as my eyes can tell). I tend to push the saturation up a tad. Play with the settings in the RAW converter to get a decent histogram but also take visual cues as to the result you are aiming for.

* Whilst many articles advise aiming for a right hand loaded histogram curve, my efforts to do so have commonly resulted in blown out highlights which means a ruined picture. If anything I tend to underexpose a touch so as to get the bulk of my histogram curve in the middle of the range.

* Dont rely on the screen to judge the final output as most (not all) screens have a colour Gamut narrower than Adobe RGB.

* Go out and shoot a couple of cards full of different shots and play with the RAW converters until you settle on one you are comfortable with.

[Roger_Cavanagh]

Martin,

The dynamic range of the 10D sensor is around 8.5 stops. This was indicated by Chuck Westfall of Canon US and I've seen, at least, two other sources confirming this. I believe I've seen the dynamic range for a bright scene quoted as 11-12 stops. so the camera can't cope with this without the photographer doing something clever with grads and filters as maderito suggests or multiple exposure (not always possible, of course).

In the absence of these options, you have to decide which part of the scene is more important shadow or highlights and meter to ensure these are exposed to show detail. A spotmeter will help with this, but using the 10D in partial metering mode is better than centre-weighted or evaluative. Plus, of course, using the histogram: to keep highlight detail don't clip to the right and ignore shadow clipping and vice versa to keep shadow detail.

Regards,

[PaulB]

Martin,
What we all have to get to grips with regarding exposure - is that there is no CORRECT exposure for any scene. There are only compromises based on what the sensor/film is capable of recording and our own personal preferences.
With film I learnt to burn and dodge in the darkroom, use graduated ND filters and polarisers on the camera.
Digital still amazes me on exposure though; my 10D will pull detail out of areas where I couldn't even see detail at the time - and I shoot mainly JPEGs.
You can either let the unimportant parts of the scene go out of gamut - is the sky or the ground the important part? - use filters to balance the exposure, or take two shots and combine them in Photoshop - one exposure to capture the sky, the other to capture the ground. Shooting RAW may allow you to process the same image twice, once to balance the sky and the other to balance the ground; then combine them for the final image. Just digital darkroom work really!

[CyberDyneSystems]

Paul,. I love your first sentence about "correct" exposure!

To often I have heard self appointed experts stating something like "well if you had taken the time to get the correct exposusre the first time..."

...and I'm allways thinking "Which correct exposure?" .. or more to the point in the case of a scene with 12 stops of range,. "there IS NO correct exposure.."

RE: Exposing to the right;

Yes I try to do it, but in the end,. I'd rather be slightly underexposed loosing some DR and color info and push it back up in the raw converter, then be overexposed.

[martcol]

Shooting RAW may allow you to process the same image twice, once to balance the sky and the other to balance the ground; then combine them for the final image. Just digital darkroom work really!

Ohmygod Paul, that is so obvious! I've had some success with combining images but it never, no never struck me that you can combine the same image! Duh! :oops: I have always bracketted and combined the results but rarely are they exactly the same with natural subjects.

So folks, you seem to be saying that it's me that can't cope with DR and not my 10D (that Lil' Beauteee)?

Thanks for all your contributions to this one!

Martin

[dtrayers]

As an exercise put the camera in partial metering mode and pick a scene of a lot of range, like a sunny day at the park. Meter dark objects and bright objects in Av mode and note how the shutter speed changes. You can count the stops between the brightest and darkest and note that before you take the shot. Then take the shot in the different metering modes.

Examine the histogram and play with the exposure compensation.

You'll get a better feel of what the camera is capable of capturing and how to anti...........................................cip ate the results.

[martcol]

...like a sunny day at the park.

Off to the park tomorrow!

Cool.

Martin

[PaulB]

Always pleased to be of assistance - especially aa I learn from other posts - and posting answers (to things I think I know something about) at least makes me rationalise why I do (and always seem to have done) things a certain way.

Speak to you all again soon I hope.

[maderito]

Martin,
Shooting RAW may allow you to process the same image twice, once to balance the sky and the other to balance the ground; then combine them for the final image. Just digital darkroom work really!
I've seen several references to this technique but no actual examples. Does anyone have an example to post.

The method of merging or blending would be key.

A simple approach: mask the blown highlights on one shot and the blocked shadows on the other and then merge.

Another possibility would be selecting a layer's transparency (ctrl-click the layer thumbnail) to select higlights and do the same but invert the selection to get shadows on the appropriate images. Then work with layers copied from the selections to get a final, merged image.

Anyone have experience here?

[dtrayers]

Here's a quick and dirty example. One RAW file, first converted to expose the sky, the second for the rocks, then combined in PS. I used the dark layer, did a levels adjustment to get the rocks really dark, used "select color" to select the dark rocks, discarded the levels layer, applied the selection as a mask and applied a 60 radius Gaussian Blur to the mask to feather it. It's faster to do than explain:

Expose for rocks
http://home.comcast.net/~dtrayers/photos/lightened.jpg

Expose for sky
http://home.comcast.net/~dtrayers/photos/darkened.jpg

Combined
http://home.comcast.net/~dtrayers/photos/combined.jpg

[PaulB]

An excellent example Dave.
The type of work I do doesn't really lend itself to this technique - I think I shall have to have a day off somewhere to get some examples I can practice on!

[yb98]

Aother example here :

http://photography-on-the.net/forum/showthread.php?t=24713&highlight=

Yacine.

[BigRed450]

For shooting outside on bright days I set the 10D exposure Compensation to -1/3. This does help protect the highlights as well as have enough recoverable detail in the shadows.....

[PekkaM]

Here's my attempt at making two different exposures from RAW and merging after that:

http://koti.mbnet.fi/~pmm/temp/1.jpg
http://koti.mbnet.fi/~pmm/temp/2.jpg

[ron chappel]

As an exercise put the camera in partial metering mode and pick a scene of a lot of range, like a sunny day at the park. Meter dark objects and bright objects in Av mode and note how the shutter speed changes. You can count the stops between the brightest and darkest and note that before you take the shot. Then take the shot in the different metering modes.

Examine the histogram and play with the exposure compensation.

You'll get a better feel of what the camera is capable of capturing and how to anti...........................................cip ate the results.

Yes!
I've been meaning to do exactly this for some time.....
maybe i should do it today and stop procrastinating :oops: :oops:

I for one have great doubts that a 10D/300D can cover 8.5 stops even in raw!
....I'll soon find out :wink:

[PhotosGuy]

More links (in no particular order) that might provide different perspectives:

Understanding Contrast Masking - 3 ways to "extend exposure".
http://luminous-landscape.com/tutorials/understanding-series/u-contrast-masking.shtml

http://www.vinberg.nu/photography/articles/technique/contrastmasking/contrast_masking.htm
digital fill-flash shadow masking:
http://www.creativepro.com/story/feature/18468-1.html

Understanding Digital Blending - Three Approaches to Expanded Dynamic Range When Shooting With A Digital Camera
http://www.luminous-landscape.com/tutorials/digital-blending.shtml

Combining 2 Different Exposures - To Hold Detail in Objects with a Large Brightness Range With a Layer Mask in Photoshop
http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

[ron chappel]

RIGHT.I did some serious testing today and found out some important facts.

Firstly and most important is the 300D does NOT cover 8.5 stops!! :x
Yes sure,you can juuuuust pick out something that might perhaps,in a pinch,maaaybe be detail in anything up to four stops each side of mid tone.But to all intents and purposes it's just scientific trivia. :twisted: :twisted:

Basically it's allways going to be a personal call as to when one gives up trying to look for detail in under or over exposed images,but most people will consider about 3.25 stops either side as white and black....and even that is pushing it!!!!
That's 6 1/2 stops folks-max

The other thing i found is that RAW is not a sure thing at getting an extra stop of brightness range :shock: :shock:
In fact in the tests i did-and i'm prepared to be slightly wrong on this because the methodology may be flawed-JPEG fine was about the same!
Maybe 1/2 a stop less overall but even then it's again a personal call because of the different colour ballance and when it cuts out.

It really is close

I look forward to seeing others' results