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Subject: "Frame rate vs. Buffer" Previous topic | Next topic
ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Thu 21-Feb-13 11:58 AM
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"Frame rate vs. Buffer"
Thu 21-Feb-13 07:56 PM by ericbowles

Atlanta, US
          

With the D7100 announcement, we've had some discussions about the frame rate and buffer. I wonder if everyone is aware of the distinctions and the impact on shooting.

For the sake of discussion, I'm using Rob Galbraith's data as a reference.
http://www.robgalbraith.com/bins/camera_wb_multi_page.asp?cid=6007-12454

Frame rate refers to how quickly the camera can release the shutter. The D7000 and D7100 are at 6 frames per second, but the amount of data captured and processed in that time is different. The D7100 spec has 6 24mp images at around 50MB each while the D7000 has 6 frames at 35MB each. Frame rate does not truly consider write speed.

Frame rate does not mean you capture the frame you need. At 1/500 sec 6 fps means you have 6/500 of the time. While you might capture small movements, you still miss 99% of the time. So moment of action still requires some skill and luck. It depends a lot on the subject. With golf, the instant when the club makes contact with the ball is so short that frame rate makes very little difference. With a large bird landing on a branch or nest, frame rate can give you several very nice images to choose from.

The buffer is the place that images are stored until they are written to the card. Larger buffers are better, but you still need to process the image into the buffer and write it to a card. The former is a function of processor speed and camera settings. The latter is a function of your card selection.

Write speed on faster cards run around 20-26 MB per second (D7000) - or less than one frame. So if you are shooting at 6 frames per second, and only writing at one frame per second, the buffer fills. But it takes 24-39 frames (edit - this number is for medium JPEGs - Raw files are much lower) to fill the buffer depending on your card. That means you can sit there and fire the camera for 5-8 seconds before the buffer is filled. That also means that once filled, the buffer takes 20-30 seconds to clear by writing all the images to the card. As camera image files get larger and without major changes in cards, a faster frame rate just fills the buffer quicker and takes longer to clear, so there is a trade off.

So in practice, for some subjects frame rate is very important but its not for everyone. And card speed is another important factor. Depending on your style and subject, you may find a fast card is needed to use a camera with a fast frame rate.

If someone is considering a D7100, getting a fast SD card is important. The big advantage of CF cards is write speeds that are nearly 50% faster than the best SD cards. And XQD has potential to be much faster than CF.

EDIT - Even a card 2-3 times as fast only allows 1-2 extra RAW files. The write speed is just under one file per second, so the buffer may fill in 11 frames instead of 10 with a card that is twice as fast. But a fast card clears the buffer faster so you are ready to shoot another burst.

Eric Bowles
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Replies to this topic
Subject Author Message Date ID
Reply message RE: Frame rate vs. Buffer
TomCurious
21st Feb 2013
1
Reply message RE: Frame rate vs. Buffer
jec6613 Silver Member
21st Feb 2013
3
Reply message RE: Frame rate vs. Buffer
TomCurious
21st Feb 2013
9
Reply message RE: Frame rate vs. Buffer
ericbowles Moderator
21st Feb 2013
5
     Reply message RE: Frame rate vs. Buffer
TomCurious
21st Feb 2013
8
Reply message RE: Frame rate vs. Buffer
dm1dave Administrator
21st Feb 2013
2
Reply message RE: Frame rate vs. Buffer
ericbowles Moderator
21st Feb 2013
4
     Reply message RE: Frame rate vs. Buffer
sabbey51 Silver Member
21st Feb 2013
6
     Reply message RE: Frame rate vs. Buffer
jec6613 Silver Member
21st Feb 2013
7
     Reply message RE: Frame rate vs. Buffer
NRousu
22nd Feb 2013
17
     Reply message RE: Frame rate vs. Buffer
TomCurious
21st Feb 2013
10
          Reply message RE: Frame rate vs. Buffer
ericbowles Moderator
21st Feb 2013
11
               Reply message RE: Frame rate vs. Buffer
TomCurious
21st Feb 2013
12
                    Reply message RE: Frame rate vs. Buffer
dm1dave Administrator
22nd Feb 2013
13
                         Reply message RE: Frame rate vs. Buffer
ericbowles Moderator
22nd Feb 2013
14
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TomCurious
22nd Feb 2013
16
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TomCurious
22nd Feb 2013
15

TomCurious Registered since 03rd Jan 2007Thu 21-Feb-13 05:53 PM
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#1. "RE: Frame rate vs. Buffer"
In response to Reply # 0


Bay Area, US
          

>>But it takes 24-39 frames to fill the buffer depending on your card

Can you elaborate on this? As the D7100 has a buffer of 6 frames when shooting lossless 14bit, how do you get 24-39? Also, how did you figure that the buffer size depends on the card?

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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jec6613 Silver Member Nikonian since 12th Feb 2013Thu 21-Feb-13 07:28 PM
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#3. "RE: Frame rate vs. Buffer"
In response to Reply # 1


Norwalk, US
          

>Also, how did you figure that the buffer size depends on the
>card?

The buffer size itself doesn't change, but even as you're filling the buffer, some of it is being emptied to the card. So if you have an 8 frame buffer, by the time you've taken two exposures you may only have one exposure of data in the buffer with a fast card, but with a slow card you may fill the buffer completely before one is written to the card.

So, effectively, with a fast card, you get a longer burst before the camera slows down to empty the buffer.

XQD cards also do some things to increase the buffer depth on the D4.

  

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TomCurious Registered since 03rd Jan 2007Thu 21-Feb-13 10:10 PM
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#9. "RE: Frame rate vs. Buffer"
In response to Reply # 3
Thu 21-Feb-13 10:13 PM by TomCurious

Bay Area, US
          

>>Also, how did you figure that the buffer size depends on
>the
>>card?
>
>The buffer size itself doesn't change, but even as you're
>filling the buffer, some of it is being emptied to the card.
>So if you have an 8 frame buffer, by the time you've taken two
>exposures you may only have one exposure of data in the buffer
>with a fast card, but with a slow card you may fill the buffer
>completely before one is written to the card.
>
>So, effectively, with a fast card, you get a longer burst
>before the camera slows down to empty the buffer.
>
>XQD cards also do some things to increase the buffer depth on
>the D4.


Thanks, but this effect is probably rather meaningless when shooting RAW. The buffer is full in exactly one second. With today's cards in the D7100 (not XQD), you probably won't get even a single 50MB file cleared from the buffer in this second, so the buffer would not be affected by the card type at all.

With JPEG of course it's different, but OP was originally about 50MB NEF files.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Thu 21-Feb-13 08:02 PM
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#5. "RE: Frame rate vs. Buffer"
In response to Reply # 1


Atlanta, US
          

Tom - I've edited the origial post. Galbraiths numbers were with JPEGs and not RAW files. Smaller files take up less space in teh buffer so you can get more frames.

Eric Bowles
Nikonians Team
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TomCurious Registered since 03rd Jan 2007Thu 21-Feb-13 10:06 PM
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#8. "RE: Frame rate vs. Buffer"
In response to Reply # 5


Bay Area, US
          

Thank Eric! The discrepancy that tripped me up was between the 50MB files you write about at the beginning (which means NEF), and then the 24-39 frames in the buffer.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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dm1dave Administrator Awarded for high level knowledge and skills in various areas, most notably in Wildlife and Landscape Writer Ribbon awarded for his excellent article contributions to the Nikonians community Nikonian since 12th Sep 2006Thu 21-Feb-13 07:04 PM
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#2. "RE: Frame rate vs. Buffer"
In response to Reply # 0


Lowden, US
          

I would expect that you can shoot at maximum frame rate for 1 or 2 shots more that the stated buffer capacity before the camera starts to slow down.

My D300s shows a buffer capacity of 17 shots (12 bit lossless compressed RAW) and I can shoot at 7 FPS for 19 -20 frames before the camera starts to slow down. I can get about 20 - 22 shots before the camera almost stops to wait for the buffer to catch up.

The D7100 (shooting 12 bit lossless compressed RAW) would I suspect you would get 8 – 10 frames at 6 FPS and then the frame rate will quickly slow over the next two or three frames.

Dave Summers
Lowden, Iowa
Nikonians Photo Contest Director

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Thu 21-Feb-13 07:45 PM
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#4. "RE: Frame rate vs. Buffer"
In response to Reply # 2


Atlanta, US
          

I think your estimate of 1-2 beyond the buffer capacity is about right for RAW files. I get around 10 images with my D600 before the buffer fills and the frame rate slows to the write speed of around 1 FPS. That's probably about the same thing we'll see with similar file sizes and the D7100.

The size of the buffer makes a big difference. That means the buffer is around the size of 3-4 image files. Said another way, you could double the frame rate, and unless the buffer is larger you would not be able to fire any more frames before the buffer is full.

Eric Bowles
Nikonians Team
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sabbey51 Silver Member Nikonian since 10th Jan 2010Thu 21-Feb-13 09:44 PM
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#6. "RE: Frame rate vs. Buffer"
In response to Reply # 4
Thu 21-Feb-13 09:45 PM by sabbey51

Saddle river, US
          

While the speed of the card plays a role, performance engineering of computer systems (read: digital cameras) is all about ensuring each of the components offers enough speed to not be a bottleneck. In a DSLR, the bottlenecks could be the frame rate, the buffer size relative to the size of the image files, the speed of the SD card, the camera's internal processor(s) (eg EXSPEED) and the internal data busses.

Many focus on the frame rate, but as the discussion in this thread points out, that is not usually the bottleneck for Raw images after the first few shots.

Many buy the fastest card possible, but again, if the internal (and unchangeable) processors and busses in the camera are only capable of say 25MB/sec, then getting a card faster than that doesn't help any.

So ... it will important to do some testing to determine the maximum write speed of the D7100 (or any other camera, for that matter) so we neither overspend on faster cards nor leave capacity unused by buying slower cards.

  

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jec6613 Silver Member Nikonian since 12th Feb 2013Thu 21-Feb-13 10:00 PM
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#7. "RE: Frame rate vs. Buffer"
In response to Reply # 6


Norwalk, US
          

Assuming it's using the same SD controllers as they've used in the D5100 and D5200, current top speed cards do not reach the maximum performance as the controller, which can handle the full speed UHS-I.

  

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NRousu Registered since 16th May 2012Fri 22-Feb-13 07:57 PM
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#17. "RE: Frame rate vs. Buffer"
In response to Reply # 6


CA
          

>Many buy the fastest card possible, but again, if the internal
>(and unchangeable) processors and busses in the camera are
>only capable of say 25MB/sec, then getting a card faster than
>that doesn't help any.
>
>So ... it will important to do some testing to determine the
>maximum write speed of the D7100 (or any other camera, for
>that matter) so we neither overspend on faster cards nor leave
>capacity unused by buying slower cards.
>

I'm hoping they've made an improvement on the bus speed. A significantly faster transfer speed would be a huge help... I love my D7000 for most things. But this issue on some shots is a downer.

  

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TomCurious Registered since 03rd Jan 2007Thu 21-Feb-13 10:15 PM
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#10. "RE: Frame rate vs. Buffer"
In response to Reply # 4


Bay Area, US
          

>I think your estimate of 1-2 beyond the buffer capacity is
>about right for RAW files.

Hm, I clicked on the link you provided, and there was no card that could handle writing of a 50MB file within the one second that the D7100 buffer would allow. How did you figure the extra 1-2 frames?

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Thu 21-Feb-13 10:26 PM
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#11. "RE: Frame rate vs. Buffer"
In response to Reply # 10


Atlanta, US
          

Tom

My thought is it takes one and a half seconds to fill the buffer which allows time to write 1 file and create capacity for a little over one more file

Eric Bowles
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TomCurious Registered since 03rd Jan 2007Thu 21-Feb-13 10:58 PM
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#12. "RE: Frame rate vs. Buffer"
In response to Reply # 11


Bay Area, US
          

Based on the specs, I figured that the buffer is full in one second when shooting 14 bit lossless NEFs, as the buffer holds 6 frames, and the camera shoots 6 frames per second. So after one second, there would be 6 frames, with about 50MB each in the buffer, for a total of about 300MB. About 2 seconds after starting to shoot (or 1 second after buffer is full and photographer is frustrated), give or take a few fractions of a second depending on the card, the very first frame would have been written to the card, the photographer would now be able to shoot one single new frame.

So the way I see it, the card would have no effect on the buffer size at all. As an aside, it does not look like a good tool for wildlife photography, compared to, say, even the D300. Of course one could always revert to JPEG, but this of course comes at other costs.

Anyway, your OP was quite informative, thanks for writing it, and this quibble I had with the buffer numbers was just a minor observation, in the scheme of things.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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dm1dave Administrator Awarded for high level knowledge and skills in various areas, most notably in Wildlife and Landscape Writer Ribbon awarded for his excellent article contributions to the Nikonians community Nikonian since 12th Sep 2006Fri 22-Feb-13 02:30 AM
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#13. "RE: Frame rate vs. Buffer"
In response to Reply # 12


Lowden, US
          

The files are not quite that big even 14-bit NEF.


NEF (RAW), Compressed, 14-bit = 28.5 MB

NEF (RAW), Lossless compressed, 12-bit = 22.7 MB


D7100 specs...

http://imaging.nikon.com/lineup/dslr/d7100/spec.htm


I think that most previous bodies have been able to shoot 1 or 2 frames more than the reported buffer size so it is likely that the D7100 will do the same. However, we will have to wait until some Nikonians have the camera in hand to see for sure.

Dave Summers
Lowden, Iowa
Nikonians Photo Contest Director

Nikonians membership -
"My most important photographic investment, after the camera"

My Nikonians Gallery | SummersPhotoGraphic.com | My Crated Gallery
----------------------------------------------------------------------------------


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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Fri 22-Feb-13 03:00 AM
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#14. "RE: Frame rate vs. Buffer"
In response to Reply # 13


Atlanta, US
          

I was assuming the buffer would also be holding lossless compressed, so their is a brief processing time, but faster write time.

The SDHC cards seem to be pretty similar in their write speed, but the CF cards seem to be much faster.

We're not saying you can overfill the buffer - just that you can shoot about an extra frame and a half due to first images being written and creating capacity.

I think you raise a good point. This all happens in 1-2 seconds and then things slow to one frame per second. That means a couple of 5 bracket sets, or just a single short burst.

Eric Bowles
Nikonians Team
My Gallery
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Nikonians membership — my most important photographic investment, after the camera

  

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TomCurious Registered since 03rd Jan 2007Fri 22-Feb-13 03:30 AM
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#16. "RE: Frame rate vs. Buffer"
In response to Reply # 14


Bay Area, US
          

No CF cards for the D7100 though.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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TomCurious Registered since 03rd Jan 2007Fri 22-Feb-13 03:28 AM
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#15. "RE: Frame rate vs. Buffer"
In response to Reply # 13


Bay Area, US
          

Thanks for correcting it! 28.5MB still won't write to the card before the buffer s full.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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