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11-21-2010, 03:08 AM   #1
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Image quality drop from ISO 12800 to 25600 on K-5

One thing we noticed in our review is that the IQ on the K-5 drops significantly as you go from ISO 12800 to 25600 and enter the expanded ISO area, especially if you're using noise reduction.

It's not just noise, it's everything when NR is on: Pentax K-5 Review - Professional Reviews

With NR off, the 25600 shot seems more acceptable: Pentax K-5 Review - Professional Reviews

Mega fail here, however:
Pentax K-5 Review - Professional Reviews

All these links go to different anchors and parameters combinations, so don't get fooled by the titles!

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11-21-2010, 05:16 AM   #2
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That's why ISO 25600 and 51200 are placed under "Extended ISO".
If you shoot RAW, convert to TIFF and work through an NR software like Topaz or Noiseware, you can get quite usable files at lower resolution.
I saved them in the end as 2MP JPEGs - very much usable for Flickr, blog posts or sending to friends on e-mail

Last edited by kittykat46; 11-21-2010 at 05:37 AM.
11-21-2010, 05:59 AM   #3
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It really seems like once you get to that range, you would be better off using a flash if possible. Clearly, post processing can help (as John Bee has shown), but they certainly use quite a bit.

Edit: My statement makes no sense. I think I meant they "lose" quite a bit (that is image quality). Bad when you have to translate your own post...

Last edited by Rondec; 11-21-2010 at 03:14 PM.
11-21-2010, 06:56 AM   #4
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Might seem a silly question but here I go but as I can't find a definitive answer anywhere I might as well be the dummy asking . The NR settings in the K-5, do these also apply to RAW? i.e. Can I turn NR off through the whole ISO spectrum and use an external NR software instead or tone down the amount of NR performed at higher ISO's?

I will clarify my reason for the question to stop people saying straight away that RAW is sacrosanct and nothing is touched or should be touched. RAW is now a format that allows the highest amount of raw data that the manufacturer thinks the camera is capable of outputting to create a useable image! So by that reasoning, in my mind it is possible to allow control over the amount of alterations (for want of a better term) performed on this data before the file is created.

11-21-2010, 07:32 AM   #5
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The "NR" which this post refers to is strictly JPEG NR. It doesn't affect the RAW file.

RAW is essentially a file which has not been subject to Lossy Compression - i.e. no data has been permanently processed out by data compression.

I don't believe ANY of the camera makers totally refrains from any form of camera-level image rendering to the signal feed coming off the sensor. The "RAW purists" really don't have a "pure" RAW file anyway in the dSLR world, I think

As a separate matter , Pentax may be applying a rather subtle low-level NR to RAW images above ISO 1600. Nothing very obvious, there is no obvious destruction of detail.
Given that, I personally don't have any real concerns there.

The K-5 RAW files are very detailed even up to ISO 51200...which make them great candidates for NR software like Noiseware.
11-21-2010, 07:48 AM   #6
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Tks for the detailed answer.
11-21-2010, 08:41 AM   #7
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QuoteOriginally posted by robbiec Quote
The NR settings in the K-5, do these also apply to RAW? i.e. Can I turn NR off through the whole ISO spectrum and use an external NR software instead or tone down the amount of NR performed at higher ISO's?
A raw file is not viewable, it is uncorrelated data. When you view a raw file, you're viewing the software's interpretation of the data. The data is displayed using the software's own rules (algorithms), so various softwares will show the file looking a little different (sometimes a lot different). Once you convert from raw to a jpeg or tiff file, all softwares will show the file in exactly the same way, using standard algorithms that are universally understood.

If you use a Pentax camera and use the Pentax supplied software to display the raw file, you are viewing an exact interpretation of the camera settings, including noise reduction. If you convert the file directly to jpeg, the camera settings for saturation, contrast etc will be used, and so will the noise reduction setting. If you don't want noise reduction applied, you must either disable it in the camera, or disable it before conversion using the Pentax software.

If you don't use Pentax software for viewing raw data and converting jpegs, then it is not so clear what the result will be (i.e. how the camera settings will be interpreted), because other softwares translate Pentax raw data using their own algorithms, including NR. You may prefer the results or not. I use Pentax DCU4 to convert to jpeg, then I use other softwares to process the jpeg.

Last edited by audiobomber; 11-21-2010 at 09:52 AM.
11-21-2010, 08:50 AM   #8
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I have the K5 only for two days, but from my experiments it seems best to turn NR off for all ISOs.
If you really want some NR, you can better do it afterwards using Neatimage or so.
Btw. I think the major quality drop is from 25600 to 51200 and not from 12800 to 25600. For me I have decided not to use 51200.

Here is an example from my room quite dark, EV = 2.

Last edited by blende8; 11-21-2010 at 09:09 AM.
11-21-2010, 10:20 AM   #9
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Well I did some nightshot yesterday at iso 51.200 and pushed them to iso 102.400 in development of the DNG's. So it's quit dark and I couldn't see some of the details with my eyes that are in the pictures like the chimnees on the roof.

Used my Nikkor 300mm/f4.5 that works with an adapter as an 375mm/f5.6 lens.






I think it's nice to use for hunting on poachers at night.
11-21-2010, 10:35 AM   #10
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Those look light night security camera images - perhaps another application for this sensor is yet to be discovered...
11-21-2010, 01:30 PM   #11
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They are of course very noisy but the really impressive thing is that I can't detect any banding. They just look like old B&W negatives.
11-21-2010, 03:08 PM   #12
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Here is my first use of the K-5s crazy good raw noise. A iso 3200 file pushed 4 stops in post (=51200)

11-21-2010, 03:30 PM   #13
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@ RonHendriks: From an aesthetic point of view these are really cool pictures! Seems like a very nice setting to obtain a grainy b/w rendition.

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