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11-11-2008, 08:00 AM   #76
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QuoteOriginally posted by kenyee Quote
I'm puzzled by that contrast adjustment too (I don't think it should have affected exposure like that). What software is that? I don't recognize the dialog boxes...
As I have said, what that function do is to sketch the histogram and redistribute the levels for the whole picture, just lifting up exposure (and increasing contrast as well, as it is sketched).

11-11-2008, 11:15 AM   #77
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QuoteOriginally posted by RiceHigh Quote
Funny that your this "drag the whitepoint to full 255" action is already and purely just pushing up exposure for the "white point" you selected as a reference point (to the brightest) for changing *both* the exposure and contrast of the whole picture, despite that it is just named "contrast adjustment". Afterall, this function *stretches* the histogram to full span and thus change *both* the exposure and contrast, nothing more, nothing less.

Btw, do you know what you are doing actually? :-)
Exposure compensation would apply to all data points. ie: it's like a multiple. increase exposure by 2x and you multiply every point by 2x..... ect.
Contrast just increases the spread from white to black.... Do you know what your talking about. I swear you know less than nothing
Technically w/ exposure compensation the shape of the histogram will not change (much). Take a grey wall and increase exposure. The peak should not spread out, only move along the axis. THIS is exposure adjustments. Stetching the histogram is CONTRAST adjustment...
BTW: Corel Photopaint
AND just a personal rant:
For those that don't like the way Pentax does things, BUY a freaking different camera...... It's not that hard people....
AND a quote from a Nikon user:
Yeah as a Nikon user I can confirm that Nikons suck at overexposing....I prefer the underexposure of the Pentaxes as most of the dynamic range is in the shadows anyway and it's easy to lift them in raw.

Sadly the best solution for Nikon's broken matrix-metering on the D40/D80 is centre-weighted metering. It's not great either but better than dialing in -2.0 exposure compensation :-S

Re: I never realized just *how* badly non-Pentax cameras overexpose...:


Re: I never realized just *how* badly non-Pentax cameras overexpose...: Pentax SLR Talk Forum: Digital Photography Review
Good photo of exposure compensation and it's global effect.

http://www.shortcourses.com/tabletop/lighting1-10.html
Just had to add this Nikon users 2 cents (I have nothing against nikon BTW)
Having the D80, which to many has the most unpredictable MM of all Nikons to date, I learned it the hard way, shooting and testing.
The present Nikon MM system depends more heavily on the focus point than other systems, or than older Nikon MM systems. This becomes a big issue if your main subject, where you point the focus to, is darker than most of the image, like a face in shade. The MM will compensate and blow the background easily.
Test this: just go outside and have a tree with leaves part in sun and part in shade. Move focus point from one to the other (w/o moving camera), using A mode. You'll se the shutter speed change accordingly.
Once you learn that, it's very reliable and predictable, and you'll likely miss very few shots.
This -0.7 uniform compensation is completely wrong IMO, it'll make many nice opps into underexposed frames.
Don't use CW, it's a step backward.
If you really want perfect exposure, learn a bit about manual exposure and use spotmetering, like I do (except for flash, then MM is just perfect, and no other maker touches the performance of Nikon's TTL flash metering).

http://forums.dpreview.com/forums/read.asp?forum=1000&message=29995589

Last edited by jeffkrol; 11-12-2008 at 07:57 PM.
11-11-2008, 12:27 PM   #78
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A friend who has a D80 also complains about overexposure all the time and leaves -1ev dialed in, so this is definitely not urban rumor ;-)

I fiddled w/ the brightness and contrast dialogs in Gimp. Brightness behaves the way you describe exposure to change. Contrast is a little different...once it hits the left/right sides, it'll stretch as you describe, but if you push it beyond that, the histogram flattens because the values clip (I think). The clipping part is what I always thought contrast adjustments did...
11-11-2008, 07:37 PM   #79
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QuoteOriginally posted by Marc Sabatella Quote
These are great examples of pictures that might be darker than you personally wanted, but *not* represent underexposure in the photographic sense. The histograms average a little left of center, just as it is supposed to. These illustrate the more conventional reason why people erroneously perceive a camera as underexposing a scene: in the absence of bright highlights that would force the camera to render a scene even darker, the main goal of the meter is to try to represent the scene as being somewhat darker than gray card on average. Meaning the histogram should average a little left of center. And that's exactly what happened in these cases.

Any book on photography will tell you that when shooting an object or scene that is lighter on average than a grey card, you need to apply expose compensation. A white wall is the classic example, and the picture of the cake you posted is in the same ballpark. *Of course* that's not the exposure you wanted, but it's absolutely the correct exposure for a meter to suggest. As always when shooting essentially white objects, it's up to you to override this to make the object *look* white, and not a little darker than a gray card. This is how SLR meters have worked for decades.
thanks marc, i need to shoot more to remember when to use how much ev. i got a good technique going using Manual and Spot Meter but that's not practical in fast situations.

personally i'd rather have the camera make the decision to meter that cake brighter, but that's just me. because i'm relatively new to SLRs, "how it always worked" doesn't really hold much weight for me.

QuoteOriginally posted by jeffkrol Quote
Here is the image and histograms. 1)Base exposure (about what I, note I expect. A mean of around 100ish.).
2)CONTRAST adjustment not exposure adjustment which would just have slid the whole thing over to the right. At least that's what "exposure adjustment" is supposed to mean. What I did is a "contrast" adjustment. Just drag the whitepoint to full 255, stretching the CONTRAST not exposure...
QuoteOriginally posted by jeffkrol Quote
Exposure compensation would apply to all data points. ie: it's like a multiple. increase exposure by 2x and you multiply every point by 2x..... ect.
Contrast just increases the spread from white to black.... Do you know what your talking about. I swear you know less than nothing
Technically w/ exposure compensation the shape of the histogram will not change (much). Take a grey wall and increase exposure. The peak should not spread out, only move along the axis. THIS is exposure adjustments. Stetching the histogram is CONTRAST adjustment...
BTW: Corel Photopaint
AND just a personal rant:
For those that don't like the way Pentax does things, BUY a freaking different camera...... It's not that hard people....
AND a quote from a Nikon user:
Yeah as a Nikon user I can confirm that Nikons suck at overexposing....I prefer the underexposure of the Pentaxes as most of the dynamic range is in the shadows anyway and it's easy to lift them in raw.

Sadly the best solution for Nikon's broken matrix-metering on the D40/D80 is centre-weighted metering. It's not great either but better than dialing in -2.0 exposure compensation :-S

Re: I never realized just *how* badly non-Pentax cameras overexpose...:


Re: I never realized just *how* badly non-Pentax cameras overexpose...: Pentax SLR Talk Forum: Digital Photography Review
Good photo of exposure compensation and it's global effect.

ShortCourses-Using Exposure Compensation
i too am confused about the contrast, i wouldn't want to use that to level out the histogram because the picture then looks way off. i like the last link you gave, that's some good info.

QuoteOriginally posted by kenyee Quote
A friend who has a D80 also complains about overexposure all the time and leaves -1ev dialed in, so this is definitely not urban rumor ;-)
more D80/D90 fun here http://forums.dpreview.com/forums/read.asp?forum=1034&message=29976021
and some D40 fun here http://forums.dpreview.com/forums/read.asp?forum=1000&message=29987797


Last edited by k100d; 11-11-2008 at 07:45 PM.
11-11-2008, 07:50 PM   #80
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Levels Adjust Contrast Brightness: Photoshop Levels Tool Adds Life to Dull Digital Camera Images
Contrast, levels, whatever...
Point Operations - Contrast Stretching
Contrast stretching (often called normalization) is a simple image enhancement technique that attempts to improve the contrast in an image by `stretching' the range of intensity values it contains to span a desired range of values, e.g. the the full range of pixel values that the image type concerned allows. It differs from the more sophisticated histogram equalization in that it can only apply a linear scaling function to the image pixel values. As a result the `enhancement' is less harsh. (Most implementations accept a graylevel image as input and produce another graylevel image as output.)
http://homepages.inf.ed.ac.uk/rbf/HIPR2/histeq.htm


http://photocritic.org/photo-contrast/
Carefully positioning the
shadow slider and highlight
slider at the point where the
data is displayed, will
increase contrast by
redistributing the brightness
levels across the range.


http://www.luzette.com/download/Using%20levels%20to%20control%20contrast.pdf





http://www.alibony.com/pse/031808levels.html


JUST for fun
http://www.vtc.com/products/AdobePhotoshopImageRestoration/ImageTypes/33708

Last edited by jeffkrol; 11-11-2008 at 08:15 PM.
11-11-2008, 08:09 PM   #81
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QuoteOriginally posted by frank Quote
Got the K20D the first day when it reached here in Singapore about 9 months back, really love the new sensor and what it's capable of. Slow AF and FPS aren't problems to me 'cause they are suffcient to my needs.

The only problem I found from this camera: there is no way you can turn off noise reduction for long time exposure! On K10D you can set noise reduction ON or OFF. But on K20D, the only two options are ON and AUTO. Luckily I haven't shot any fireworks w/ the K20D camera yet, but I know I'd be pissed if I use it for fireworks. Don't know if this thing can be fixed by firmware, but seem Pentax don't think it's important.

Other than this, I'm pretty happy w/ the camera.
Sorry, I don't quite understand.

Does this mean the k20D cannot take long expsoures such as 30 sec, 40sec, etc?

How does NR on/off affect the camera?

Thanks
11-11-2008, 08:16 PM   #82
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Ahh..searched the forum and now i understand. K20D need to pause for a long period of time after each long exposure shot and this is making shooting fireworks impossible.

Hmm....I wish Pentax would release a firmware fix to this.
11-11-2008, 08:28 PM   #83
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QuoteOriginally posted by raider Quote
K20D need to pause for a long period of time after each long exposure shot and this is making shooting fireworks impossible.
Not quite. Have a look at my gallery.
Contains two fireworks shots taken with a K100D which I deliberately set to "NR on". Yes, had to wait a little and perhaps missed some moments but got plenty of good ones.

What about not losing a moment but not having an image worth looking at because it is too noisy? While dark frame subtraction may work in many cases, perhaps it isn't that easy with a K20D? I have difficulty in believing the engineers just wanted to allow their users to have one complaint left to point out.

11-11-2008, 09:16 PM   #84
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The only Flaws I ever seen with the K20d is the operator.
11-11-2008, 10:35 PM   #85
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QuoteOriginally posted by k100d Quote
thanks marc, i need to shoot more to remember when to use how much ev. i got a good technique going using Manual and Spot Meter but that's not practical in fast situations.
My recommendation is to do what I do - use center-weighted all the time. That way there is no delay while you change from other mode to one that will work reasonably well. One nice thing about center-weighted is that it won't try to hard to protect highlights (because it is incapable of identifying them), meaning you don't get "underexposed" pictures for that reason when just pointing and shooting. And yet it can also be used as a spot meter (with a very wide spot). With practice, you can get as fast as you need to be.

QuoteQuote:
personally i'd rather have the camera make the decision to meter that cake brighter, but that's just me. because I'm relatively new to SLRs, "how it always worked" doesn't really hold much weight for me.
Understandable. I think an option to enable a mode like that would make sense. But really, there's simply no way for the camera to know that cake was white. Our eyes are amazing things, the way they adjust and are able to recognize a white object as being white even in dim light, when it in reality is no brighter than a black object in full sunlight. Cameras are not really able to tell the difference. So in practice, there is just no way around the need to to learn a bit why cameras meter as they do - there are *reasons* things have always worked this way.
11-12-2008, 02:35 AM   #86
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QuoteOriginally posted by Gooshin Quote
REALLY??!

which canon dlsr model has a built in focusing motor in the body, please tell!
Unless I'm totally missing something here, don't all Canon DSLR's bodies have an internal focusing motor?
11-12-2008, 05:37 AM   #87
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QuoteOriginally posted by daleroy Quote
Unless I'm totally missing something here, don't all Canon DSLR's bodies have an internal focusing motor?
Quite the reverse actually: none of them have one. The EF and EF-S mount are fully electronic, with no mechanical coupling between lens and camera. That means all EF and EF-S compatible autofocus lenses must have some form of in-lens AF motorization.
11-12-2008, 05:52 AM   #88
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QuoteOriginally posted by RBellavance Quote
Quite the reverse actually: none of them have one. The EF and EF-S mount are fully electronic, with no mechanical coupling between lens and camera. That means all EF and EF-S compatible autofocus lenses must have some form of in-lens AF motorization.
Well, you learn something new everyday they say. Thanks for that.
11-14-2008, 02:58 AM   #89
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Can not turn off Noise Reduction for long time exposures

The only thing (so far) stopping me from buying the K20D is the fact that you can not turn off the noise reduction in low ISO for long time exposures.

I had a friend of mine buy the K20D basically on my recommendation. He was going to get the Canon 40D, he wanted to see what my K10D was like and looked at the features of the K20D, I told him he could borrow my DA* lenses if he got the K20D, as well as other stuff I had. That sold him on the camera.

I was saddened to see that when doing night shots on 100 or 200 ISO, you can't turn the noise reduction off so you got to put up with waiting for 20 or 30 sec after you take the photo before you can take another shot. I can turn this off on my *istDL and my K10D but not on the K20D!!!!

Pentax, if you are reading this..... NOT HAPPY JAN!!!!!! NOT HAPPY AT ALL!!!!
If you can not fix this issue, like in a software update, then sadly I may have to look at another brand of camera.

I shoot a LOT of time exposure photography, so as good as the camera is, without the ability to do full manual photography and NOT have to wait for ages after taking a photo before I can take the next, I will be looking at other cameras. Sadly I would love to stay with pentax, I have used pentax gear (when shooting for myself) most of my 30+ years of taking pictures.
11-14-2008, 03:29 AM   #90
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[QUOTE=Vatis;393453]The only thing (so far) stopping me from buying the K20D is the fact that you can not turn off the noise reduction in low ISO for long time exposures.

Pentax, if you are reading this..... NOT HAPPY JAN!!!!!! NOT HAPPY AT ALL!!!!
If you can not fix this issue, like in a software update, then sadly I may have to look at another brand of camera.

I shoot a LOT of time exposure photography, so as good as the camera is, without the ability to do full manual photography and NOT have to wait for ages after taking a photo before I can take the next, I will be looking at other cameras. Sadly I would love to stay with pentax, I have used pentax gear (when shooting for myself) most of my 30+ years of taking pictures.[/QUOTE

The current version of the K20D's Samsung sensor is not well suited to your needs. Turning off NR on long exposures would reveal too many hot pixels. Time to move on. What's so sad about that?
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