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Old Apr 20, 2010, 7:38 PM   #11
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I would look at the pentax k-x or the canon T1i or T2i. All three are very good to 6400iso, and can shoot at 12800. The canon has an advantage over the pentax, as canon has more fast lenses at 1.4 and 1.8 that are not super expensive.
I can't check doxmark now as on my phone but there was a reason for suggesting the K-m over the Canons, I think it was the dynamic range at the medium high isos or was it just things were so similar that price was the main aspect.
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Old Apr 21, 2010, 6:50 AM   #12
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Just for clarification... I think Mark means the K-x (which is a newer model using a Sony 12MP CMOS Sensor that does quite well at higher ISO speeds). The Pentax K-m (a.k.a., Pentax K2000) is an older 10MP model using a Sony 10MP CCD Sensor (as your Pentax K10D uses).

Yes, the DxoMark tests are very interesting for the new Pentax K-x. I had not looked at them before now. What's quite interesting is how well it does on the DR tests.

http://www.dxomark.com/index.php/eng...base/Pentax/Kx

Other tests I've seen don't show it doing quite as well (with DR dropping off to around 7.7 stops at ISO 1600 shooting JPEG), with less highlight room compared to some of it's competitors, given a properly exposed mid gray.

Ditto for raw tests using Adobe Camera Raw (better results with RAW compared to JPEG, but not quite as well as some of the competing models, with very little "headroom" for recovery of overexposed areas. See what dpreview.com found here. The best they could do with ACR shooting in RAW was 9.9 stops with lots of tweaking (whereas DxOMark measured considerably more DR with their tests of it).

http://www.dpreview.com/reviews/pentaxkx/page17.asp

Given conflicts, I'd take some of those tests with a "grain of salt", as the raw converter being used can make a big difference, as can things like Black Point settings and how the image is exposed (and dpreview.com's jpeg tests assume a properly exposed mid gray). It looks like DxOMark probably had more optimum settings for their tests (and they test the RAW files).

Also keep in mind that DxOMark is using extrapolated test results for Pentax dSLR models at higher ISO Speeds. That's why you'll see the graph points change from solid to white at higher ISO speeds.

With the Pentax K-x, they're only extrapolating above ISO 1600 though (that's the only speeds they've detected a problem that would skew their results, but that doesn't mean that other things are going on at the raw level that they haven't detected yet either). That's because their tests have indicated that Pentax dSLR models are applying noise reduction at the raw level, even with it turned off. So, rather than using actual measurements, they extrapolate the results at ISO speeds where they've detected manipulation of raw data to give you a better idea how well they compare. See this article for more info about that part:

http://www.dxomark.com/index.php/eng...Pentax-cameras

But, other camera models tend to do the same type of thing. For example, some Sony models do it, and some Olympus models do it.

I've seen very strong evidence of Nikon doing it with some of their models. They're just doing it in a more subtle way that DxOMark hasn't detected yet (so, they're not using extrapolated results for Nikon models yet). See this post for some analysis of raw data before the demosaic process for what Nikon appears to be doing with some models:

http://forums.dpreview.com/forums/re...ssage=32401883

Nikon also appears to be performing long exposure NR at the raw level with some models, even with long exposure NR turned off. Here's an article discussing it:

http://www.astrosurf.com/buil/nikon_test/test.htm

They also appear to do other types of preprocessing of raw data. For example, Dave Coffin (the author of dcraw.c ) noticed that Nikon was modifying raw data years ago with some of their cameras (applying multipliers to raw data). That type of preprocessing can also skew results. See question #12 from this interview with Dave in 2005:

http://www.dpreview.com/news/0504/05...ninterview.asp

In fact, I had a long conversion with Dave the night before that interview was published (we were mostly discussing Nikon's encryption of RGB multipliers for White Balance at the time, and he had offered to do an interview with Steve's at the time, too).

IOW, those types of approaches (manipulation of data at the raw level from cameras) can skew test results, making it harder to compare cameras, since most of those types of tests are not looking at actual retained detail and you may end up with less real headroom in raw files from some cameras when manipulation is being performed, making it harder to do things like highlight recovery in overexposed areas, given proper exposure of mid tones.

Lighting temperature can also enter the equation due to differences in transmission characteristics of the Bayer Filter Array over the sensor (different response curves, requiring more correction for some lighting versus others to get a usable, color corrected image, which can also impact those types of test results). Applying multipliers to raw data can also skew test results.

IOW, tests can be useful for generalizations. But, I would not take them as absolute measurements of how one camera compares to another without looking at the images being produced in the conditions you plan using them in, comparing retained detail from one camera versus another. For example, a camera with a great S/N ratio and looks good on other tests may not necessarily have a lot of retained detail in the final images; or a camera that tests well using a lighting temperature of 5500k may not do as well in the final images after color correction when shooting in typical indoor tungsten type lighting (where you'd be more likely to use higher ISO speeds). ;-)
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Old Apr 21, 2010, 6:52 AM   #13
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Quote:
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Just for clarification... I think Mark means the K-x (which is a newer model using a Sony 12MP CMOS Sensor that does quite well at higher ISO speeds). The Pentax K-m (a.k.a., Pentax K2000) is an older 10MP model using a Sony 10MP CCD Sensor (as your Pentax K10D uses).
Oops, yes it was just gone 2.30am when I posted that and there are so many different names I'm getting confused. So K-x not K-m.
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Old Apr 21, 2010, 7:02 AM   #14
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Now, having said all of that, the Pentax K-x does do quite well at higher ISO speeds from images I've seen. Pentax has managed to squeeze a lot out of it, with more retained detail at higher ISO speeds compared to it's competition. So, it should be a big improvement over your K10D for use in lower lighting should you decide to upgrade your camera body and want to stay with Pentax.
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Old Apr 21, 2010, 9:29 AM   #15
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Wow Jim C, that is tonnes of useful information and a lot to digest. Thank you for taking the time to write it all... It is fascinating to lean more about the way the tests are run and the way manufacturers manipulate the data.

Of course what I really need is a camera shop to let me try out several models in the conditions I would use them, so I can see if I perceive a real difference in the final image quality. The K10d (which I bought second hand) looked great on paper, but has been disappointing in reality. Unfortunately I have not yet found a shop that will let me do this...
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Old Apr 21, 2010, 10:46 AM   #16
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You could always rent before you buy.

See LensRentals.com.

They don't have Pentax gear, but they have Canon, Nikon and Sony. And they have the Sigma 30/1.4 in all three mounts.
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Old Apr 22, 2010, 6:18 PM   #17
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So, I having read lots online I set off to buy a Pentax Kx (having found someone interested in buying my K10d) but the camera shop persuaded me that I should get the Canon 500d instead as it was the same price and, he said, a much better camera for the money. I told him that I had read a lot about the kx high ISO performance, but he said tests were not the same as real world experience.

Eventually he said that I could buy it and try it, then exchange it for a kx and try that, and exchange them back again if I decided I preferred the Canon... (which he was sure I would)

So, I have photographed a rehearsal with the 500d and the kit lens. It is way better than my K10d at colour matching and for noise levels at high ISOs. I loved the Live view monitor and liked the handling and feel of it.

The image quality is much better, but I am not blown away by it. (however I am lighting verdi's Macbeth at the moment which is as dark and contrasty as my shows get and a challenge for any camera.) So I'm going to swap it for the kx and see how it compares. I will put samples of shots from all 3 online after tomorrow's rehearsal.

Do you have any general thoughts about 500d v kx? I thought the kx was going to be much cheaper, but here in France they are pretty much the same price. Ultimately I will need to get a fast prime lens as well, but that will have to wait a while.

Thank you
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Old Apr 22, 2010, 6:31 PM   #18
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Default K10d v 500d images

Here are some images of the same scenes shot on different days on the k10d and 500d

500d is much better, but would kx be better still? I hope to find out tomorrow.

K10

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500d

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K10 2

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500d 2
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500d 3
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Last edited by Mr.P; Apr 22, 2010 at 6:34 PM. Reason: adding detail
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Old Apr 22, 2010, 6:36 PM   #19
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Default and some more

K10 are the noisier ones
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Last edited by Mr.P; Apr 22, 2010 at 6:39 PM. Reason: wrong photo uploaded
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Old Apr 22, 2010, 6:37 PM   #20
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The K-x may not be better as those are really taking in a dark environment. And the k-x may not be able to get a focus lock. But if it can, there may be deal a bit better the the 500D with noise but not by much.
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