Pentax as first DSLR?

Started Jul 17, 2013 | Discussions thread
Alex Sarbu
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Re: Actually you are wrong
In reply to Ivan Gordeli, Jul 23, 2013

Ivan Gordeli wrote:

kikivrany wrote:

I always keep in mind that DOX compared in some tests 8Mp down sample files when I look at there results. There are a lot threads about it.

They do it to offer a meaningful comparison for practical print sizes. Basically it means that for print sizes up to 12x18 (inches). So unless you print bigger than that, it is a very good comparison.

The problem is that they're not printing, even though they're calling that "print"; they're simply scaling the results with some factor. Also, they're not measuring things like detail in their tests. DXOMark is a limited value synthetic benchmark.

Some sort of normalization is required, though, when comparing cameras with different pixel count. With them, a simple downscaling could be enough.

Furthermore for the particular example of 16MP APS-C and 13MP full frame sensor it doesn't matter much if you normalize to 8MP or not, you can see it by looking at screen level graphs and compare them to the normalized ones (actually there is a small difference further in favor of the 5D by not normalizing). This is because the difference in MP count is small (16 vs 13) (the 16MP APS-C sensor has ~ only 1/2 stop noise advantage due to more megapixels if you normalize).

I can't follow your conclusion, even with the DOX results...let's look for that at ISO 100 or simple at ISO higher than 3200.

At ISO 100 the SNR, Tonal range and color sensitivity are about the same for all 3 cameras. Noticeable advantage for the Pentax is in dynamic range (2 stops more), this advantage is quickly decreasing with increasing ISO and by ISO800 5D passes the K-30.

The normalized results are better for the APS-C cameras, except for SNR (unsurprisingly, as AFAIK the shot noise should be significant in those measurements). The overall score is higher for the APS-C cameras, and actually the K-5 IIs and the K-5 II are rated higher than any Canon FF model. Are you sure you want to continue using DXOMark data? Strange things are happening, with synthetic benchmarks.

Alex

 Alex Sarbu's gear list:Alex Sarbu's gear list
Pentax K20D Pentax K-5 Pentax smc DA* 60-250mm F4.0 ED (IF) SDM Pentax smc DA 21mm F3.2 AL Limited Pentax smc DA 70mm F2.4 AL Limited +4 more
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