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09-24-2010, 02:43 AM   #1
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K-5 / K-7 : eight raw buffer limit exists

My theory about why the eight raw buffer limit exists (also with an accordingly low JPEG buffer limit) at maximum continuous rate is Pentax's typical conservative specification policy and the existence of these extremely high maximum ISO's in extended ISO mode. To me, it makes sense that the actual raw buffer limit is just proportionally less than that of the K-7 considering the larger pixel dimensions and the faster continuous shooting speed, such that 15 raw captures would seem to be about right for exactly the same shooting environment and ISO sensitivity settings. However, there very well might be only eight raw captures possible for worst case raw files sizes where the maximum raw file size at ISO 51,200 could be as large as 35 MBytes or so.

Thus, there is no discrepancy between the performance of the K-7 and this new K-5 ( as "Which" website says in its video review: Videoclips about Pentax K-5 Digital Camera ), and only confusion about the conditions under which that limit applies.

09-24-2010, 03:17 AM   #2
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Camera manufacturers are not exactly renown for their conservatism when producing specs.

What worries me more than the 8 raw file buffer is the seemingly inability to cope with high burst even at the Lo setting. The K7 blows the K5 out of the water. Published data :

K7 : Hi: 5.2 fps to 40 frames (JPG), 15 frames (PEF), 14 frames (DNG)
Lo: 3.3 fps until card is full (JPG), up to 17 frames (PEF/DNG)

K5 : Continuous shooting Hi: 7 fps to 22 frames (JPG), 8 frames (PEF/DNG),
Lo: 2 fps until card is full (JPG), up to 12 frames (PEF/DNG)

Kr : Hi: 6 fps (25 JPG, 12 RAW),
Lo: 2 fps (unlimited JPG, 36 RAW)

Even the Kr seemingly has a larger buffer and I find this a confusing anomaly. I would love to know what is going on here and what the real world scenario is.
09-24-2010, 04:14 AM   #3
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This is one spec that is hard to ignore.
I'd have thought if output was going to be significantly greater in future models (both in terms of file size and speed of capture) then there should also be a image processor upgrade.
09-24-2010, 04:21 AM   #4
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Yep, that buffer size really confuses me. Why K-5 buffer is so much shallower?

RAW data size and buffer are following:
  • K-r 12.4Mp @ 12 bit = 18.6MB. Max 12 RAW frames 12 18.6 = 223.2 MB
  • K-7 14.6Mp @ 12 bit = 21.9MB. Max 15 RAW frames 15 21.9 = 328 MB
  • K-5 16.3Mp @ 14 bit = 28,5MB. Max 8 RAW frames 8 28.5 = 228 MB

I am not sure if that's the right way to calculate buffer size, however note, that K-5 and K-r buffer size, calculated as above, is almost identical.
Could it be that K-5 shares main board with K-r and that's why buffer is so much smaller than on K-7?

09-24-2010, 05:09 AM   #5
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As i already mentioned on other threads, the brochure from pentax at PK, states 15 RAW with 7 F/s...

So i would not start whining about something which really only looks like a rumor
09-24-2010, 05:12 AM   #6
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Well I was told it all comes to a good end in productionmodel as I was told at the PhotoKina. Here from the brochure, sorry I only pict up the german one and forgot the english version:




Last edited by Nass; 09-24-2010 at 06:30 AM. Reason: adding [imgwide] tags
09-24-2010, 05:18 AM   #7
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Second picture under "Serienaufnahmen" you will find a hind to the buffer size
09-24-2010, 05:31 AM   #8
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PENTAX K-5 The flagship model of PENTAX K digital SLR camera series, offering high-quality images and user-friendly operation to satisfy the demands of advanced amateurs
Continuous Shooting Max. 7.0 fps, JPEG (16M: starstarstar at Continuous Hi): up to 22 frames, RAW: up to 8 frames

Pentax K-5 - Digitale Spiegelreflexkameras - PENTAX Europe Imaging Systems
Serienaufnahmen: Hi mit ca. 7 B/Sek 40 JPEG- oder 8 RAW-Aufnahmen

K-5 - Official PENTAX Imaging Web Site
Continuous FPS - Continuous Hi: 7.0 FPS (22 JPG, 8 RAW) - Continuous Lo: 2.0 FPS (unlimited JPG, 12 RAW)


Pentax has made one big mess with those K-5 specifications which are different everywhere....

09-24-2010, 06:24 AM   #9
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QuoteOriginally posted by Edvinas Quote
Pentax has made one big mess with those K-5 specifications which are different everywhere....
That's so true.
09-24-2010, 06:32 AM   #10
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If it is true(for sure) that the K-5 can only do 8 frames in RAW or a 2 FPS alternative... then I'd have to admit that I'll be sorely disappointed with Pentax's K-5 design. So much in fact that I might have to rethink my upgrade strategy. Buffer shooting is perhaps one of the most relied-on part of my K20D's working feature I use for gigs. I typically shoot RAW in the buffer during an entire event and I simply can't see myself ever loosing this option.

Without sounding like a whiner, I'd have to voice that if the K-5 came with an 7FPS. 8 shot RAW buffer and a 2 FPS alternative, that I will most likely cut my losses, and build a new kit off the D700.

I guess the extent of my sentiment at this stage is...
I jut hope I'm wrong
09-24-2010, 06:36 AM   #11
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QuoteOriginally posted by Frogfish Quote
K5 : Continuous shooting Hi: 7 fps to 22 frames (JPG), 8 frames (PEF/DNG),
Lo: 2 fps until card is full (JPG), up to 12 frames (PEF/DNG)


Even the Kr seemingly has a larger buffer and I find this a confusing anomaly. I would love to know what is going on here and what the real world scenario is.
It doesn't have a larger buffer(in theory), it has to do with the size of each image. K-5 files will be significantly larger with 4 million more pixels to process each time. Therefore it has to do more work each time an image is captured.

But what really bothers me is the Lo setting...
According to this, if in Lo mode, you will actually slow down to below 2fps after shooting 12 frames. Well this is after 6 seconds of shooting so it doesn't matter right? Well, I figured that after 8 frames in Hi speed that it would slow to about 3 or 4 fps, but according to this, it will slow down below 2fps.....Anybody else find that really uncomforting? It will pretty much come to a dead stop after 8 frames....
09-24-2010, 06:41 AM   #12
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QuoteOriginally posted by Frogfish Quote
Camera manufacturers are not exactly renown for their conservatism when producing specs.

What worries me more than the 8 raw file buffer is the seemingly inability to cope with high burst even at the Lo setting. The K7 blows the K5 out of the water. Published data :

K7 : Hi: 5.2 fps to 40 frames (JPG), 15 frames (PEF), 14 frames (DNG)
Lo: 3.3 fps until card is full (JPG), up to 17 frames (PEF/DNG)

K5 : Continuous shooting Hi: 7 fps to 22 frames (JPG), 8 frames (PEF/DNG),
Lo: 2 fps until card is full (JPG), up to 12 frames (PEF/DNG)

Kr : Hi: 6 fps (25 JPG, 12 RAW),
Lo: 2 fps (unlimited JPG, 36 RAW)

Even the Kr seemingly has a larger buffer and I find this a confusing anomaly. I would love to know what is going on here and what the real world scenario is.
note that a higher fps with the same physical size buffer will fill the buffer faster. the buffer size in terms of frames is a function of data in - data out. If data in is coming 53 % faster (K5 to Kr based on maximum frame rate and difference in pixel count), and data out is at a constant rate, but with 25% more frames coming out of a K-r due to its lower resolution then yes, there will seem based on specified frame rate only a smaller butter on the K-5, but in reality I don't think so.

Similarly the K7 to K5 comparison needs to consider that the K7 is a 14.1 MP camera the K5 is a 16.28 MP camera, so the bufer is getting hit with more data in, and at a higher frame rate.

the short explanation is that you need to look at data in and out, measured in bits, or pixels perhaps, but NOT in frames.
09-24-2010, 06:59 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
the short explanation is that you need to look at data in and out, measured in bits, or pixels perhaps, but NOT in frames.
I still think that K-5 has smaller buffer than K-7.

K-7 fills buffer at 110MB/s
14.612/85≈110MB/s

So, in three seconds (15 RAW images) K-7 mumps in into buffer ≈330MB
K-7 writes data to SD card at ≈15MB/s, so in three seconds it would free up 45MB.
So, K-7 buffer should be 285MB.

K-5 fills buffer at 200MB/s
16.314/87≈200MB/s

It's almost double compared to K-7.
K-5 will make 8 frames in 1.14 seconds, during which it will pump into buffer 228MB of data. It will write to SD card ≈17MB. That makes K-5 buffer only 211MB...

Of course these are only approximate calculations, however they give overall picture about buffer size of K-5.

Last edited by Edvinas; 09-24-2010 at 07:17 AM.
09-24-2010, 07:13 AM   #14
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QuoteOriginally posted by Edvinas Quote
I still think that K-5 has smaller buffer than K-7.

K-7 fills buffer at 110MB/s
14.612/85≈110MB/s

So, in three seconds (15 RAW images) K-7 mumps in into buffer ≈330MB

K-5 fills buffer at 200MB/s
16.314/87≈200MB/s

It's almost double compared to K-7. K-5 will pump 330MB into buffer in ≈1,6-1,7 sec. Having 7fps it is easy to calculate that K-5 should manage to fire off 11-12 RAW frames in this time interval. But it does not. And that means that K-5 has smaller buffer than K-7.
But what about the data OUT of the buffer.

you are allowing only one half of the equation. What is the MB out of the buffer to the flash card. how fast does this get out, this will impact greatly the calculation you have made on the buffer the faster the transfer rate, the smaller your buffer will get (from the 330MB you indicate) and the fewer images you can put into it before it is full.
09-24-2010, 07:16 AM   #15
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QuoteOriginally posted by Lowell Goudge Quote
But what about the data OUT of the buffer.

you are allowing only one half of the equation. What is the MB out of the buffer to the flash card. how fast does this get out, this will impact greatly the calculation you have made on the buffer the faster the transfer rate, the smaller your buffer will get (from the 330MB you indicate) and the fewer images you can put into it before it is full.
It does not affect it much. I have redone calculations assuming that buffer is freed up at ≈15MB/s.
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