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Author Topic: 1D X FPS limiting factor?  (Read 7524 times)

PackLight

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Re: 1D X FPS limiting factor?
« Reply #30 on: December 29, 2012, 12:43:21 AM »
Yes sensor size is a factor in determining file size, take the 7D sensors pixel density and make the sensor FF size. See how that affects file size.


Sensor size does not determine file size. How many times we need to tell you this?
Are you measuring size in area, or size in number of pixels...... One of you is arguing with one definition, one with the other....

Given the same degree of compression and a/d bit depth, an APS C sensor and a FF sensor with the same number of megapixels will produce the same size file.

BUT....
If you are arguing based on pixel density, then to scale up an 18M APS C  to FF physical size, you could fit 46M pixels into the area of a FF sensor and of course the file would be bigger

All Crop sensors have less MP than full frame. They do not like me saying file size has anything to do with the physical size of the sensor. Of course two sensors with equal pixel density, the larger produces a larger file. Were not supposed to relate these two in this discussion though. They want to be hard core sticklers and say file size is controlled only by the number of MP, which is somewhat correct except there are a few other factors involved.

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Re: 1D X FPS limiting factor?
« Reply #30 on: December 29, 2012, 12:43:21 AM »

tpatana

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Re: 1D X FPS limiting factor?
« Reply #31 on: December 29, 2012, 02:58:39 AM »
They want to be hard core sticklers and say file size is controlled only by the number of MP, which is somewhat correct except there are a few other factors involved.

Argh... it's pretty much correct.

Crop size 18MP and FF size 18MP give exactly same file sizes, assuming algorithm and such is same.

lethalfalcon

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Re: 1D X FPS limiting factor?
« Reply #32 on: December 29, 2012, 03:41:52 AM »
To answer the OP, I'm pretty sure the limit is in the mechanical shutter, however, like Mt. Spokane mentioned, it's likely that the capabilities of the processors and the buffer are matched to the limitations of the shutter mechanism. It makes no sense to over-engineer something if it can never be used. If they could get 14FPS with the shutter moving, they wouldn't have needed it locked, and it would have been better for them if they could have allowed focusing at 14FPS. Saying JPEG only is not dependent on whether the shutter moves, either. Also, it should have been (relatively) easy to slap more buffer RAM on the board if it were needed to handle more data.

Card speed is definitely a limiting factor, though, but more on the continuous shooting side. If you put 1GB of buffer memory into the camera, but it takes 8 seconds to clear it (and that's with Lexar 1000x cards), once you fill that buffer you're going to be waiting if you want to burst again. They might be able to fit 4GB on there, but then you need to wait half a minute to write the whole buffer out. I think the processors can handle a bit more than the 150MB/s of data the card can, especially if you're shooting clean images (ISO 100). The more noise and the more cleaning functions you turn on, the more you'll tax the logic. And they could always go for more chips if they can find the room. Think quad Digic 5+. :)

As to the later posts about file sizes, consider this: a 7D and a 1DX are really close to the same MP (same written image size of 5184x3456). However, a 1DX takes FAR cleaner images under almost all circumstances. Cleaner images = better compression. The idea is that a cleaner image is likely to have more pixels that have the same value, so the compression algorithm can more efficiently store that. If every pixel is a different color (because it actually is or because of noise changing the output just slightly), compression falls apart. I just took two pure white images (.6" ISO100 no lens, shot at a lit wall) from a 7D and a 1DX. Both show they're completely blown out in LR. Results: 14,498,781 bytes for the 1DX and 14,223,956 for the 7D. I'd guess that 200KB is mostly extra metadata.

rs

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Re: 1D X FPS limiting factor?
« Reply #33 on: December 29, 2012, 04:17:38 AM »
All Crop sensors have less MP than full frame. They do not like me saying file size has anything to do with the physical size of the sensor. Of course two sensors with equal pixel density, the larger produces a larger file. Were not supposed to relate these two in this discussion though. They want to be hard core sticklers and say file size is controlled only by the number of MP, which is somewhat correct except there are a few other factors involved.

Not all crop sensors have less MP than full frame. The original Canon 1Ds was full frame with 11MP, the original Canon 5D had 12MP, whereas the latest generation of APS-C Canon's have 18MP.

However, if what you're on about is scaling up the current generation of crop sensors to FF, along with the appropriate increase in MP, then you'll end up with a 46MP FF sensor (18MP x 1.6h x 1.6v). That would result in more data, but the extra data is directly proportional to the MP increase. For two sensors of equal MP, the sensor size has no effect on the amount of data (other than the larger sensor potentially producing lower noise levels, allowing even the RAW files to be compressed more, as stated by lethalfalcon)
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EchoLocation

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Re: 1D X FPS limiting factor?
« Reply #34 on: December 29, 2012, 08:14:56 AM »
All Crop sensors have less MP than full frame. They do not like me saying file size has anything to do with the physical size of the sensor. Of course two sensors with equal pixel density, the larger produces a larger file. Were not supposed to relate these two in this discussion though. They want to be hard core sticklers and say file size is controlled only by the number of MP, which is somewhat correct except there are a few other factors involved.
As has been said above, All crop sensors do not have less MP than full frame sensors.
What do you want from this thread exactly?
There have been numerous discussions on numerous different aspects of files size in relation to sensor size, MP, compression algorithims, and whatnot...
It was pretty clear from the second or third post that no one knows exactly which aspect of the 1DX limits the FPS. There are many different areas of concern that are all near (80%ish) of their capabilities.
There are many different opinions on this but no hard facts, we've heard many opinions(many from good sources) so far, but obviously you haven't heard one that satisfies you.
What exactly are you looking to hear? that the file size and Digic V's are the limiting factor(to corroborate the story you remember)? i'm a little confused on what we are arguing about at this point besides your lack of satisfaction from the answers given.
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Don Haines

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Re: 1D X FPS limiting factor?
« Reply #35 on: December 29, 2012, 09:01:22 AM »

All Crop sensors have less MP than full frame.
The T3i and the 1D-X have the same number of pixels...... That's right..... an obsolete rebel has the same number as the just released flagship.....care to restate that statement?
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Re: 1D X FPS limiting factor?
« Reply #36 on: December 29, 2012, 09:23:06 AM »
They do not like me saying file size has anything to do with the physical size of the sensor. Of course two sensors with equal pixel density, the larger produces a larger file. Were not supposed to relate these two in this discussion though. They want to be hard core sticklers and say file size is controlled only by the number of MP, which is somewhat correct except there are a few other factors involved.

The file size produced by the sensor is 5184 pixels X 3456 pixels X 14 bits X 3 colors, all divided by 8 bits per byte for one of Canon's current 18M sensors. That's a 94M file. That is the size of the file an 18M sensor produces... Period! And does not matter if it is in a iD-X or in a point and shoot.

The camera then runs lossless compression algorithms to create the data for the raw file, plus adds in some overhead, such as the Exif data. The size of the .raw file depends on the algorithm used and the nature of the image. Complex algorithms will compress more than simpler algorithms, but at the cost of needing a lot more computing power.... But at the level we are talking about with Dslrs, the difference is minimal.

It is the nature of the image that has the most effect on .raw file size..... Look at the images on your computer and good luck finding two of he same size.... Try taking two images, one of a properly exposed scene with lots of variation (no big areas of the same color) and the other picture with the lens cap on..... That's the effect of image scene and that's about 99.9 percent of what affects file size
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Re: 1D X FPS limiting factor?
« Reply #36 on: December 29, 2012, 09:23:06 AM »

rs

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Re: 1D X FPS limiting factor?
« Reply #37 on: December 29, 2012, 09:27:54 AM »
what is limiting the maximum FPS for the 1D X?

is it the bandwith/processing power of the DIGIC5+ CPU´s?

or is it the mechanical shutter construction?

could a dual digic 5+ powered camera deliver 10 FPS for a 21-24MP sensor?

To return to the original question, the 1D X as far as I know is beyond any SLR before in terms of frame rate for a moving mirror at 12 FPS, and also beyond any DSLR's data throughput at 216 MP/s (18MP 12 times each second, it's max in RAW mode).

While both of those are pushing the boundaries, as to which is forming the actual limit, only the Canon engineers will know. However, it's likely the mirror assembly is moving as fast as they could get working reliably at that price point, and the data throughput of the dual digic 5+ at 12 FPS would have been pushed too far with one of the many 20+ MP sensors they have put in every other full frame body released since the 1Ds mk III.

Therefore they're probably both right up at their respective limits, in balance with each other.

To answer your last question, based on the above assumption of an upper limit of 216 MP/s, at 10 FPS a dual digic 5+ camera could work with a sensor of up to 21.6 MP. Any more MP and the frame rate would have to drop further.

And the rumoured 46MP camera with the same processing pipeline would max out at 4.7 FPS - if it's 50+ MP, it'll be 4.3 FPS or less.
« Last Edit: December 29, 2012, 09:38:04 AM by rs »
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Re: 1D X FPS limiting factor?
« Reply #37 on: December 29, 2012, 09:27:54 AM »