Pentax as first DSLR?

Started Jul 17, 2013 | Discussions thread
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Ivan Gordeli Forum Member • Posts: 70
Re: Actually you are wrong

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.

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.

You can not directly compare the cameras at ISO above 3200, because the Canon does not have ISO >3200.For the explanation why it is not a problem see below.

Now my English is not the best, so maybe I misread this sentence from you:

...(Of course the 5D does not offer ISO higher than 3200, however for either the 5D or the K-5 shooting at ISO above 1600 gives no advantages other than convenience.) ...

Did you mean under 1600 instead of above 1600, because I for example must use ISO's above 1600 a lot when I make ballet pictures for my daughter. And I'm glad my K5 has this ISO range.

Generally speaking high-ISO (between ISO400 and ISO3200) performance of the 5D is (slightly) better than K-5. You can see it both from the DXOmark score and also from the graphs (except for DR, where the K-5 has ~1/2 stop advantage). Quite impressive from a 8 year old model, isn't it? 5D does not offer ISO higher than 3200, however this is a minor drawback, because the K-5/K-30 or 5D does not give any advantage of shooting above ISO1600 anyway. In a sense that you can fully replicate the results of higher than 1600 ISO by using the ISO1600 and pushing as much as you need in postprocessing, which you can do automatically. In fact in the case of Pentax SLRs shooting at lower ISO (1600) will give you more control over the final result than going above ISO1600, because those SLRs start to use NR above ISO1600 even if you set highISO NR to OFF (if we believe dxomark of course). dxomark has a special note on that.

You can see from the graphs and from a special note from dxomark (you can see that the data points for the Pentax cameras are not the bold dots anymore starting at ISO3200, which means the Pentax simply is interpolating and using NR after ISO1600).
This means that you will get exactly the same results if you take a picture at ISO1600 with the 5D or with the Pentax K-5/K-30, then push it when processing by 1 stop and apply NR you will get the same result as with K-5/K-30 at ISO3200. Or you can get the same results by taking a picture with the Pentax at ISO1600 and pushing it 1 stop when processing and applying the NR. It is not an issue if you shoot RAW and it is a minor annoyance if you shoot JPEGs only.

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