Ad
Ad
Ad
Pages: « 1 ... 5 6 [7]   Bottom of Page
Print
Author Topic: canon 1d mark III  (Read 29779 times)
Ray
Sr. Member
****
Offline Offline

Posts: 8949


« Reply #120 on: March 02, 2007, 07:41:39 PM »
ReplyReply

Quote
I wouldn't put too much hope in that.  The blackframe read noise of a mkIII 14-bit RAW at ISO 100 is 4.88 ADU.  Translated to 12-bit, that's 1.22, a modest gain over the ~1.26 of the mkII (and perhaps just a camera-specific thing; the gain could vary a little from copy to copy).  The mkII data goes up to about 3711 on the clipped specimens I've seen, and the blackpoint is 128, so there are about 3583 12-bit levels.  The mkIII RAWs I have clip at about 15280 and have a blackpoint of 1024, so they have about 14,256 14-bit levels, or about 3,564 12-bit levels.  Since ISO 100 doesn't even use close to full well, it should be linear right up to clipping, with no hidden extra highlights.

[{POST_SNAPBACK}][/a]

John,
I notice that the comparison shots at Imaging Resource, [a href=\"http://www.imaging-resource.com/PRODS/E1DMK3/E1DMK3A5.HTM]http://www.imaging-resource.com/PRODS/E1DMK3/E1DMK3A5.HTM[/url] , show the the 1D3 at ISO 6400 as having virtually the same performance as the 1D2 at ISO 3200. With both cameras at ISO 3200, the 1D3 seems noticeably cleaner. With both cameras at ISO 1600, the differences seem reduced but the 1D3 still marginally better. I imagine if we could see comparisons right down the ISO scale to ISO 100, the differences would gradually reduce to the point where at ISO 100 there would be no noticeable difference except marginally greater resolution on the line charts.

If this is so, it confirms my impression that the DR improvements are directed at high ISO performance only.

Nevertheless, it looks as though Canon have provided a real ISO 3200 in this camera, which is better than using the same exposure at ISO 1600.

Also, I'm wondering what the implications of the 10 frames per second speed might be for hand-held bracketed shots. Clearly, there has to be a minimum shutter speed for this, but I don't recall seeing it mentioned. For example, 10 exposures at 1/20th sec would take up 1/2 a sec, allowing a maximum time of just 1/20th sec to reset the sensor for the next exposure.

I wonder if it would be possible to bracket exposures at high ISO, using IS, and get shots for blending which are effectively as good as tripod shots?
Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8949


« Reply #121 on: March 02, 2007, 08:09:47 PM »
ReplyReply

Quote
Your explanation of the exposure factors seems reasonable, but it might be that the illumination inside the church of the first picture at ISO 100 with particularly bad shadow noise and banding was very low.

That has to be the explanation. It's just curious that whenever I decided to use ISO 100 for this type of shot, the dynamic range of the scene appears to have been much greater than those occasions when the lighting was so bad I needed to use a high ISO.

Quote
In post-Christian Italy were there any locals worshiping in those churches or was everyone a tourist?   

I could count on one hand the number of occasions a service was being held at the time I visited a church. Most of the time, just masses of tourists swirling around. Pretty similar to Angkor Wat in that respect.

We have to accept that Italy is the greatest repository of art in the world, by far I would think.
Logged
jani
Sr. Member
****
Offline Offline

Posts: 1604



WWW
« Reply #122 on: March 03, 2007, 04:43:27 AM »
ReplyReply

Quote
Also, I'm wondering what the implications of the 10 frames per second speed might be for hand-held bracketed shots. Clearly, there has to be a minimum shutter speed for this, but I don't recall seeing it mentioned. For example, 10 exposures at 1/20th sec would take up 1/2 a sec, allowing a maximum time of just 1/20th sec to reset the sensor for the next exposure.
It's not just a matter of resetting the sensor, the mirror and shutter need their time, too.

See page 61 of the white paper:

Quote
Continuous Shooting Speed: Approx. 10 fps (at a shutter speed of 1/500 sec. or faster
in all recording modes)
Logged

Jan
Ray
Sr. Member
****
Offline Offline

Posts: 8949


« Reply #123 on: March 03, 2007, 07:28:51 AM »
ReplyReply

Quote
It's not just a matter of resetting the sensor, the mirror and shutter need their time, too.

See page 61 of the white paper:

Quote
Continuous Shooting Speed: Approx. 10 fps (at a shutter speed of 1/500 sec. or faster
in all recording modes)
[a href=\"index.php?act=findpost&pid=104380\"][{POST_SNAPBACK}][/a]

In that case the 1D3 is not going to be fast enough for handheld bracketed shots for blending purposes. The interval between, say 1/500th and 1/2000th at ISO 1600 is going to be just slightly shorter than 1/9th sec. Too much scope for camera shake I'm afraid.
Logged
bjanes
Sr. Member
****
Offline Offline

Posts: 2884



« Reply #124 on: March 03, 2007, 08:59:43 AM »
ReplyReply

Quote
As far as log output is concerned (I think you probably really mean gamma-adjusted; 0 has no log), the real issue is the read noise, and having a gamma-adjusted output from an ADC is not going to reduce the signal-to-read noise ratios, and the diodes or transistors used would probably add more noise of their own.
[{POST_SNAPBACK}][/a]

Actually, a gamma adjusted encoding is not good for HDR (high dynamic range) images because the slope of the curve becomes infinite towards zero luminance, and the steps at low luminance are very large, leading to posterization. This is why the sRGB curve has a linear segment at low luminance. The linearly encoded raw file is a limited form of HDR encoding, but it wastes bits at high luminances and requires a large number of bits to represent the data, hence Canon's upping the bit depth of the 1D M3 to 14 bits from 12--hopefully, they know what they are doing. A log encoding would be more efficient and has proportionally equal encoding steps throughout its range, but it can't represent zero luminance. However, at very low luminances the digital images contain little information due to noise and a encoding of these values may not be warranted, since they are often clipped in the final output. Floating point encoding has properties similar to log encoding.

As [a href=\"http://www.anyhere.com/gward/hdrenc/hdr_encodings.html]Greg Ward[/url] notes on his web site, for most of the history of photography, we have used HDR encoding with negative film, which has a log response. This paper is a good source of information for various types of encoding, and Greg discusses the factors that are mentioned above. For example, sRGB has a useful log base 10 DR of 1.6 or 40:1.
« Last Edit: March 03, 2007, 09:16:32 AM by bjanes » Logged
bjanes
Sr. Member
****
Offline Offline

Posts: 2884



« Reply #125 on: March 03, 2007, 09:14:06 AM »
ReplyReply

Quote
In that case the 1D3 is not going to be fast enough for handheld bracketed shots for blending purposes. The interval between, say 1/500th and 1/2000th at ISO 1600 is going to be just slightly shorter than 1/9th sec. Too much scope for camera shake I'm afraid.
[a href=\"index.php?act=findpost&pid=104393\"][{POST_SNAPBACK}][/a]

If you had an accurate way to register the images with sophisticated software, perhaps blending would be possible with hand held shots. In Debevec's previously mentioned paper, he derived the irrradiance curve for the Memorial Chapel from 16 photographs processed from PhotoCDs, which do not scan precisely the same image areas each time around. He used normalized correlation to obtain subpixel registration among the various images.

Bill
Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8949


« Reply #126 on: March 03, 2007, 06:04:58 PM »
ReplyReply

Quote
If you had an accurate way to register the images with sophisticated software, perhaps blending would be possible with hand held shots. In Debevec's previously mentioned paper, he derived the irrradiance curve for the Memorial Chapel from 16 photographs processed from PhotoCDs, which do not scan precisely the same image areas each time around. He used normalized correlation to obtain subpixel registration among the various images.
[a href=\"index.php?act=findpost&pid=104405\"][{POST_SNAPBACK}][/a]

Bill,
I have no doubt that a program could be written to handle this. Perhaps one already exists, but I haven't come across it. However, I think there's a difference between images that are merely misaligned on an actual 2-dimensional plane (as in scanning) and images that are misaligned due to 3-dimensional camera shake, which might consist of any combination of tilting, twisting, rotating,  back/forward and sidewards movement.

Whever I've tried manually aligning layers for blending (from handheld shots) at high magnification in order to get pixel accuracy, I've failed to get all parts of the image perfectly aligned simultaneously.
Logged
jani
Sr. Member
****
Offline Offline

Posts: 1604



WWW
« Reply #127 on: March 04, 2007, 04:25:43 PM »
ReplyReply

Quote
In that case the 1D3 is not going to be fast enough for handheld bracketed shots for blending purposes. The interval between, say 1/500th and 1/2000th at ISO 1600 is going to be just slightly shorter than 1/9th sec. Too much scope for camera shake I'm afraid.
I don't understand why you appear so surprised.

Nobody seems to have claimed that the 10 fps performance of the 1D Mk III has been any quicker than 10 fps, and it seems self-evident that these must be at least close to evenly spaced across a second.

It doesn't matter if you're at ISO 1600, or if the shutter time is 1/500 or 1/1000000 of a second.
Logged

Jan
Ray
Sr. Member
****
Offline Offline

Posts: 8949


« Reply #128 on: March 04, 2007, 05:57:12 PM »
ReplyReply

Quote
I don't understand why you appear so surprised.

Nobody seems to have claimed that the 10 fps performance of the 1D Mk III has been any quicker than 10 fps, and it seems self-evident that these must be at least close to evenly spaced across a second.

It doesn't matter if you're at ISO 1600, or if the shutter time is 1/500 or 1/1000000 of a second.
[a href=\"index.php?act=findpost&pid=104648\"][{POST_SNAPBACK}][/a]

I'm not really surprised, but I see there's a point of logic here that escaped me when I raised the question. If the camera were able to shoot 10 fps at 1/20th second exposure, then it would surely be able to manage more than that at 1/500th, which it can't as you point out.
Logged
jani
Sr. Member
****
Offline Offline

Posts: 1604



WWW
« Reply #129 on: March 05, 2007, 04:03:05 AM »
ReplyReply

Quote
I'm not really surprised, but I see there's a point of logic here that escaped me when I raised the question. If the camera were able to shoot 10 fps at 1/20th second exposure, then it would surely be able to manage more than that at 1/500th, which it can't as you point out.
If it could manage more at 1/500th, Canon wouldn't sell it as a 10 fps camera, they'd sell it as a "more than 10 fps" camera, and using whichever value of fps that it could crank out at its max speed.
Logged

Jan
Pages: « 1 ... 5 6 [7]   Top of Page
Print
Jump to:  

Ad
Ad
Ad