K20D & "Expanding the dynamic range"

On page 79 of the K20D Operating Manual it explains how to expand the dynamic

range. I understand how to turn this off and on, but I don't understand what it

does and when it would be advisable to use it. Can someone please explain this?

Thanks

My understanding of the feature is the camera can expose bright and dark areas of an image better. This is one area where good quality film can still outperform a digital camera a bit better. So for example, if the foreground is dark and the sky bright, the limited dynamic range ( or luminosity range) of the camera would blow out the sky and properly expose the foreground or expose the sky correctly and have the foreground too dark.

 

With this feature on, the camera will do a better job of exposing both. The dynamic range of our eyes is about 25 and cameras of this quality have a range of 5-7 (Db). I don't know what the increase in dynamic range with the feature turned on is but it should do a better job in balancing the exposures between light and dark areas. I saw some examples of this with a guy and his dog in the snow on a bright sunny day. Normally if the snow was exposed correctly with good detail, the subjects would be dark because the shutter speeds would be so high that the dog or person would be underexposed. His shots looked good and well exposed in both areas.

 

My question is why this feature wouldn't be used all the time? Is there some quality loss with it enabled? Also what is the increase in DR when it's on?

Peter, I don't think decibels and stops are the same thing. The numbers you quote regarding dynamic range are light stops. I'm not sure what the stop increase is with expanded DR, but it sets the base ISO to 200, so draw your own conclusions as to what you lose in IQ.

I'ld like to see examples of this in use if you can post. Much appreciated.

 

I called Pentax tech support yesterday to lower the contrast setting through the

firmware for my K100D and it seems they went ahead and did this for the K20D but

called it another name.

 

Even shooting RAW doesn't fix HDR scenes and this would be interesting to see how

this feature worked.

I ran my own tests. Here is the setup:

 

Bright late afternoon sun

Shoot on manual

ISO 200 for each shot. Exposure settings identical

Shoot DR on and DR off

All images shot in PEF RAW

 

The shots are of a neighbors 4 wheeler. Lots of contrast. Note the garage door in the background showing lots of white, and the open door next to it with dark.

 

When I made the shots with EDR on and EDR off, the only thing I noticed after the shot was that the garage door "blinked" in the LCD due to clipping when EDR was off. When it was on, I didn't get the clipping.

 

The difference in the shots was not apparent, so in ACR, I cranked up the recovery slider to 100% which brought the highlights down. I also brought up the fill light to 50% to see about bringing out shadow detail.

 

Summary of results: The main difference can be seen if you zoom in to the garage door detail. Most of it is preserved in the EDR on case, where it is mostly clipped with EDR off. No difference in shadow detail or noise could be seen. Here are the photos:

 

http://www.flickr.com/photos/arena5/sets/72157604871666311/detail/

 

I'm still at a loss to see the 200%. Wouldn't a 200% increase mean a 2-stop increase in DR? There is not even a 1-stop increase as far as I can tell, on either the high or the low end. If EDR were going to show itself, it would have done so here. The effect is very subtle, bordering on unobserveable.

Comments?

I bet the IQ is about the same as 100. The reason is sometimes the sensor lowest ISO isn't it's native ISO.

 

For instance Canon 1D series went to ISO 50 but the native ISO was 100 (or maybe it was 100 and native 200) but the point is the K10D or K20D could have a native 200 ISO and still use ISO 100.

 

Generally the only advantage of the lower ISO is for things were you'd want slower shutter speeds, IQ is usually the same at 100 and 200.

 

Again, I'm assuming the native ISO is something but ISO 100.

 

As far as the DR expansion, it's designed to give you more stops of exposure. Fuji sensors have this expanded DR on the S3 and S5. Basically the fujis can gain about 4 stops over a normal exposure but I've seen varying degrees of this being true. Whatever the case fujis do tend to get a bit more DR. I suppose though it's like SR, your mileage will vary from user to user and scene to scene.

Mis yes you're right sorry. The dynamic range is in stops. Duh

S, I actually like the shot with no EDR better. Hmmm....

In his multi-part examination of theK20D over on The Online Photographer, Carl Weese said he didn't think the extended dynamic range feature should be left on as a default setting, because it makes some captures look "plastiky" like they'd been worked over with heavy noise reduction. But not all. i didn't fully understand his explanation but i bet we are in for a bit of a trip getting a real handle on this feature.

also in S's examples, on my screen there is more highlight detail in the door with the EDR switched off! Are the captions switched, S?

That is really odd. They are not switched. On any monitor I look at, the EDR "on" (the one on the right) has more detail in the white garage door. In the one on the left: EDR off, the highlights are blown and I can see almost no detail.

Very weird. At first I saw the same results as David, but then I noticed the pictures were open in the wrong order ("on" first). Some subtle subconscious tab opening process is interfering!

 

EDR really works then. Some people say all it does is to underexpose (expose to the right) and then bring the levels up to the right exposure (thus increasing noise)., you can do the same in post-processing.

But "expose to the right" is to "overexpose" isn't it? The effect is so subtle that I still don't see what the big deal is. It certainly isn't an increase of 200% in dynamic range!

I can see the differences but it's subtle. Since it's processed in RAW, you can't tell

what part is ACR and the Pentax feature. Looks to me only a differently shaped

contrast curve was applied, but what software. Wonder if it works on jpegs?

 

Where I'ld like to see this applied is on shots of bright blue sky with billowous clouds

backlighting a big tree in the foreground and see if you can make out the bark detail

on the shaded tree trunk.

"Wonder if it works on jpegs?"

 

It certainly does! And it probably makes more sense to use it when shooting jpegs than with RAW. I think I was reading the test of one of the Olympus cameras (maybe a Fuji?) with this feature and it *only* worked on jpegs.

I agree with Mis. It would benefit JPEGs most, as highlights are more possible to blow out. In the test samples, I notice the "on" version to have a lighter exposure of dark areas, where the highlights remain the same or less. The trade off is likely to mean less contrast- so not always desirable.

 

Tim, why reduce the K100D contrast in firmware- why not just shoot in "natural" mode, which certainly does reduce contrast, and/or reduce the contrast setting?

This latest review confirms it is simply a "highlight clipper preventer"

 

http://www.cameralabs.com/reviews/Pentax_K20D/lens.shtml

 

"EDR" must have been coined by Marketing, not Engineering

Michael,

 

I am shooting in "Natural" mode with the lowest contrast setting available.

 

Here's an example of what I'm dealing with at the bottom showing that even shooting

RAW doesn't help. I've seen plenty of DSLR's reproduce this type of shot just fine. I

ETTR'ed as much as I could.<div></div>

Not unusual for a DSLR in general. And no doubt the reason for the special designing of K20D and K200D, having DR problems in mind. Digital is closer to slide film in narrower exposure latitude, and the reason many wedding photographers still shoot with Kodak Porta 160 print film.

 

Someone shooting Fuji Velvia ISO 50 can easily run into the same kind of problems. Here is one example I have saved taken with very saturated higher contrast print film. This is a scan suppied on CD, but the print looks similar.<div></div>

You can see that with high-contrast scenes, highlight loss is nothing new in the areas with very bright lighting. A neutral density filter is one way it has traditionally been dealt with.

Nice shot of the Merc, Michael.

 

The density of the shadows indicate you could've underexposed even more to get the

color of the guy's shirt to hold up without blowing out.

 

I just read a review in a magazine that the new K200D (K100D replacement) and the

rest of the new line of Pentax DSLR's all have this Extended DR setting with K200D

now having weather sealing as did the K10D.

 

Always a day late and a dollar short.

Although print film is still best for dealing with this issue, and particularly with flash, it seems, I do think digital has improved its performance compared to several years ago. Here is a couple of examples taken with the K100D last summer using all default and bright setting. This flower shot shows excellent metering choice of balance by the camera (matrix metering) in both shadows being open just enough, while preserving good detail of highlights under extremely bright conditions, with very good gradation of tones in between. And these are JPEG shots in AV mode.<div></div>

We have to remember, even the human eye can be faced with near-blinding reflections. But what it also does is close and open the pupil according to which part of the scene the eye is trained upon- where the camera captures the whole scene as one. Very important to realize that difference. Once capture is made as is, we try to entertain the idea we can look at the image the same way as we could the live scene!!

 

Here is the second example- if we were there, we could glance upward where the sun is reflected and our pupils would close down, cutting the glare. Then we could glance down and the pupils would open to see the person in shadow. I think the camera has done a good job in a somewhat compromised but effective capture of the whole in one visual gulp.

 

In many scenes, if we back down contrast too much, the overall result looks flat. Even moreso if we make a print.<div></div>

I posted a test that demonstrates how the EDR function on the k20d protects the RGB levels as well, so even if brightness is not blown, color is preserved.

 

Note: the wagon is supposed to be RED.

 

EDR OFF

 

<a href=" title="RedWagonEDR_off by arena_5, on Flickr"><img src="http://farm4.static.flickr.com/3084/2508691649_ebc762b0f8.jpg" width="500" height="333" alt="RedWagonEDR_off" /></a>

 

EDR ON

 

<a href=" title="RedWagonEDR_on by arena_5, on Flickr"><img src="http://farm3.static.flickr.com/2168/2508692067_23491ba5d3.jpg" width="500" height="333" alt="RedWagonEDR_on" /></a>