Pentax K-x sensor kicks some serious A$$ !

[Darren Addy]

We get questions regarding what DSLR to purchase fairly regularly here, so:

DX0Mark is a great place to check out how your camera's sensor compares to the competition. I recently found a deal on a low mileage (1150 shutter actuation) Pentax K-x which I have been drooling over for a while so I ran some comparisons. Here's how the Pentax K-x compares to its Big Brother (the flagship Pentax K7) along with the Canon 550 (T2i) and Canon 50D. The K-x contains the 12.1 mp Sony Exmor sensor. The results are all the more remarkable when you compare prices:

Amazon Prices:
Canon 50D (body alone) $999
Canon T2i (body alone) $979
Pentax K7 (body alone) $844
Pentax K-x (with 18-55mm DAL lens) $506

Obviously, the sensor inside the camera is only one aspect of the camera and there may be other features that over-ride the RAW image quality of the sensor... so your mileage may vary. Also, DX0Mark allows you to compare apples to oranges (APS-C sized sensors against full-frame sensors) if you want to.

 

[Greg Campbell]

DXO is 'interesting,' but I'm not sure how useful it is. Even if it serves as a consistent scale by which to compare various camera's sensors, it says nothing about usability, ergonomics, construction, etc., all of which are, IMO, far more important in the the real world.

I'm sure you're aware that DXO's dynamic range spec is completely out of touch with reality. They somehow come up with 10.8 stops of DR for my old Drebel XT. In practice, I get usable detail in Zone 8 (+3 stops) down to Zone 1 (-4), and there's plenty of noise down in those shadows. That makes 7 stops of useful data. I can't imagine what they're smoking that allows them to 'see' 12 stops on your Pentax.

 

[Darren Addy]

First, keep in mind that they are measuring RAW.
Second, even if we accept your premise that their methodology is on crack you can still make some valuable inferences as long as their methodology is consistent for all cameras/sensors.
Thirdly, I'm not so sure they are on crack. In this thread, BobF displays a personality disorder but also explains that the results (if you understand them) are quite similar between dpreview and DX0 in the dynamic range category.

This article compares the (fullframe) Nikon D700, the Nikon D5000, and the Pentax K-x. (It is a WIN for the $513 K-x to even be in this discussion considering the respective price tags of the Nikons.) The D5000 and the K-x share the same 12.1mp Sony Exmor sensor. The conclusion: The fullframe D700 is #1, the K-x is #2, the D5000 is #3 but "all are very close".

His conclusion:

Traditionaly, there is a one stop difference between full frame and APS-C. Temporarily, this sensor (Nikon D5000, Pentax K-x, supposed to be a Sony Exmor sensor) fills the gap (towards a Nikon D700) with respect to dynamic range while the difference remains with respect to high ISO noise.

This means that the D5000/K-x sensor has the same sensitivity to light as usual (as the D700) but has significantly reduced read-out noise.

The Pentax K-x may have a slight advantage over the Nikon D5000, esp. at very high ISO values. At the same time, this sensor (or firmware library) seems to include raw data alteration which makes the numerical analysis even more difficult, even when done in the DxO way. The time for true signal measurements has come, defining random noise as the sample variations of the signal and fixed pattern noise as the difference of the mean value with the ideal signal.

Lab tests (our own and the ones published by DxO) make the D5000/K-x have better dynamic range than the D700. But this is due to the limited testing methodology. D700 still has the better dynamic range, but by a small margin only.

 

[Tom Mitchell]

DXo mark is highly suspect, and frankly, irrelevant to evaluating an camera as part of an imaging system.

The fact of the matter is that all Dslrs on the market today will perform admirably, and remarkably similar. And the DxO guys admit it. If you dig shooting test charts, then maybe the results are relevant, but the variables involved in real world shooting completely overwhelm the subtle differences in todays sensors. You will be hard pressed to find a one sensor that will perform perceptively better or worse than another relative to the skill of the operator in using the system.

DXo does allow you to compare apples to oranges. As long as you can make sense of how a statement like "apples have 20% more fructose/acid ratio than oranges" applies to why one is red and the other is a blend of yellow and red, then it can be useful.

The old adage is even more true than ever..."The most important parts of a camera are in front of the lens and behind the eyepiece."

 

[Darren Addy]

The thing about old adages is that (while often true) they don't tell the whole story. The equipment is not irrelevant.

I read lots of people going ga-ga over the high ISO performance of the K-x (people who have handled or owned lots of DSLRs). I think that a very good argument could be made for making the "High ISO" performance of a camera one of its most valuable features. We are all going to run into situations where we wish there was more light to work with.

If you don't think that is valuable, then price the difference between a 300mm lens that has a maximum aperture of f5.6 vs one that has a maximum aperture of f2.8. My K-x ISO 6400 shots look like my K200D's shots at 1600 (maybe better). I've just made all of my lenses the equiv. of 2 stops faster.

Now if you already have an investment in lenses of a particular camera mount, I'm not saying you will want to go out and switch. But if you are looking at your first digital DSLR you are in a different category. It might seem like all cameras are basically the same.

Breaking down what is important to you in a camera may be harder than adopting the attitude than they are "all the same". Most people just buy what their friends are buying. But I'm just saying that if you understand the variables that are important in photography and you look at the offerings with an eye to those things, there just isn't another camera in the price range that even comes close to the Pentax K-x. And the heart of the reason is the Sony Exmor sensor.

Dx0's results just confirm why people (who aren't using Dx0's methodology - just shooting the camera and looking at the results) are going ga-ga over it.

 

[Greg Campbell]

Darren, the only people going ga-ga over DxOMark are Pixel Peepers and Gear Dweebs!

You aren't, by chance, trying to justify your Stormtrooper camera purchase, are you? It sounds like that evil device has sucked you over to the dark side - into a hellish realm where the art of photography has been reduced to arguing over useless technical 'specs.' What happened to the noble film shooter I once knew?


R.I.P.
Darren Addy
Photographer
???? - 2010

 

[Darren Addy]

LOL@Glen

There are many ways of defining brain death, but I think it occurs when one starts reading/believing Ken Rockwell.
(People are going ga-ga over the results of the camera, not the Dx0 specs.)

PS...Film is for my Pentax Z-1p and my Canon TX.

Anybody wanna compare ISO 6400 (no post-processing) JPEGs straight out of the camera?

-Darren

 

[Jim Saueressig]

I can send some K-7 samples into the batch but the K-x beats it to death in high ISO.

As far as the charts I can't speak for them but in the real world the K-x has generally beat the pants off of any camera that even comes near it in price or functionality.

And yes Rockwell is a fraud. Wasn't he the whiner that went all emo over some internet tax and started begging for more donations or he would have to quit being a fraud because he wouldn't be able to survive with a few cent tax?

 

[Greg Campbell]

"KR = Brain Death" LOL, Derwood!

I agree that KR is best taken is small doses. I enjoy his blathering, and appreciate the random occasions when he makes a valid point. ('7 levels,' 'Your Camera does not Matter,' etc.) As Jim mentions, his constant begging for $ and hits does get mighty old. The dude drives a Mercedes and is constantly buying $$$ German Glass to play with.

I will say this for him: He is out there shooting, and he appears to be having fun doing so. That sets him miles above the masses of Gear Dweebs who spend more time on forums fretting and arguing over meaningless details and specs than they do behind the lens. 'Photography' is NOT about the camera, or pixels, or red lines on your lens, or comparing pictures of brick walls and test charts; it's about recording some aspect of your personal experience, preferably in a manner you deem aesthetic.

- Not Glenn Campbell

 

[Darren Addy]

'Photography' is NOT about the camera, or pixels, or red lines on your lens, or comparing pictures of brick walls and test charts; it's about recording some aspect of your personal experience, preferably in a manner you deem aesthetic.

That's a wonderful philosophy, Greg, and one I happen to agree with! "Photography" can be enjoyed with any kind of camera. However the thread I started was not about the essence of "Photography". It was about a particular camera that I believe deserves serious consideration for anyone in the market for a DSLR (and explaining the heart of the reason it is getting such warranted attention).

Regarding camera selection criteria: Hey, you can get from Point A to Point B in any car that runs, and some people will buy on looks or because their neighbor has one, or whatever. But some people want to do some research and choose on criteria important to them. In the camera department the bottom line for most people is IQ (image quality) - taking into consideration the cost (bang for the buck).

For those not afraid of a little objective IQ comparision (rather than esoteric sensor measurements) here's a nice article showing examples of the K-x to other models at high ISOs: http://www.imaging-resource.com/PRODS/KX/KXA.HTM (starts halfway down page). You don't have to have a lot of visual acuity to notice the difference.

Between the dynamic range and high ISO performance (two hugely important metrics) it is particularly surprising to find one of the best camera to also be one of the most affordable. That being said, I'll be happy to keep such discoveries to myself in the future, if they are unwelcome here.

 

[Darren Addy]

One other clarification (or point for discussion).

In the "old days", photographers had two main choices: Their camera and the film they put in that camera. Two friends might own different brands of cameras, but they could still both shoot Velvia or Vericolor or whatever. Some photographers would settle on a particular film because they liked it's characteristics (speed, grain, color response, the light they were shooting in: daylight/tungsten).

In the digital age, many of those decisions that used to be put into film choice are now put into post-processing. We can change white balance after the fact (also in-camera), we can apply noise reduction (soften the "grain"), etc. Most people understand that post-processing involves a certain degradation of the image. We try to make that imperceptable (and it most certainly is on a low resolution device like a computer monitor, unless we are really ham-handed at it). But I think we'd all agree that the more we have to work with in the RAW file, the easier our job of producing a great image is after-the-fact.

We can also choose to shoot at different ISOs (in-camera) but the crucial difference is that the performance you get from your ISO setting is dependent upon one thing: the sensor and the on-board (and off-board) processing of the signals that it generates. You can't change that. So in a sense, your choice of camera is much different than your choice of camera was in the film days.

Your choice of camera is doing two main things:
1) You are choosing the "film" you will be shooting with for every single shot (the sensor) and
2) You are choosing the lens mount that you will need your lenses to fit (or adapt to).

This is why "pick a camera, any camera" may be fine for some, but will take more thought for others.

 

[Greg Campbell]

Between the dynamic range and high ISO performance (two hugely important metrics) it is particularly surprising to find one of the best camera to also be one of the most affordable. That being said, I'll be happy to keep such discoveries to myself in the future, if they are unwelcome here.

I wasn't trying to shoot you down, Darren! I was just trying to inject an alternate POV into what was promising to become a hardcore Gear Dweeb discussion. If anything, I should bow out and let you pixel peepers have at it.

Enjoy...

 

[Darren Addy]

Compare the noise in the shots of your DSLR at the following ISOs with these:
http://www.flickr.com/photos/29738823@N02/sets/72157622549473808/detail/
(not my shots)

The Pentax K-x at ISO 6400 and 12,800. You may not need to shoot at those ISOs every day, but when you have to it is nice to know that your results will be more than passable.