January 31, 2015, 07:08:28 AM

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Messages - jrista

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1
EOS Bodies / Re: More About the EOS 5DS & EOS 5DS R
« on: January 30, 2015, 01:37:35 PM »
So this is a camera optimized for low ISO performance. Canon is talking about stronger CFA and all of that....(which, given that for color depth above 24 bits is basically indiscernible to the human eye, is a total waste of time IMO. The only potential benefit MIGHT be lower color noise, if they are more finely restricting the colors through each CFA...but color noise would also be reduced if they would reduce their darn read noise.)


But once again...utter silence about read noise and dynamic range. This is, clearly, a Low ISO part from Canon. If they had resolved their low ISO read noise issues...one would think they would be proclaiming it to the heavens. Why the silence? :\


I don't want to lose the last little bit of hope I have in Canon...

2
EOS Bodies / Re: More About the EOS 5DS & EOS 5DS R
« on: January 30, 2015, 01:35:15 PM »
Who makes the NEW Sensor ??? The administrator over at Sony Alpha Rumors is bleating that's it's probably a Sony Sensor.

Of course he's often wrong about claiming wishful thinking to be truth ;)


I highly doubt it. It sounds like the new sensor has the same pixel pitch as the 7D II, and Canon has long been proud of their "fully integrated in house" approach. I'll believe it has a Sony sensor when someone tears it apart and actually finds a Sony sensor inside...and I personally believe hell will freeze over on that day. :P

3
EOS Bodies / Re: Bingo! New Canon 5Ds has 50.6 MP new rumored specs
« on: January 30, 2015, 01:29:34 PM »
Interesting about the ISO, but for this particular camera (5Ds...studio camera, pplz! ;P), I truly don't think it matters. It's got a good mp count and the nice big frame, which should be better for landscapes. I really couldn't care about much more than ISO 800 tops for landscapes.


The only thing I really care about is...what's the read noise? Did Canon fix their DR issues, or not? If not, then I still don't care if it's 50mp, 80mp, or 100mp...I'd still get a D810.

4
Landscape / Re: Deep Sky Astrophotography
« on: January 29, 2015, 05:48:00 PM »
Great stuff, guys! Your really progressing!


One piece of advice: Try to get longer exposures, rather than stacking tons of short exposures. Noise does average out, if it is the right kind of noise. Thing about read noise, it adds in a certain way, and it does NOT average out like dark current noise or photon shot noise.


Here's the math (simplified a bit, it ignores other factors that I don't want to get into with you guys yet):


SNR = (n * S)/SQRT(n * (S + D + R^2))


n = sub count
S = signal
D = dark current
R = read noise


Notice here...R is SQUARED in the square root term. That basically makes it a constant. While everything else is scalar, R is squared, so it compounds as you combine more and more frames. It's the one kind of noise you have to watch out for, as if you combine lots of frames (115, for example) the read noise starts to add up, while all the rest of the noise averages out. The signal is combining as well, and the signal grows faster than the read noise, but read noise does not average out like everything else, so you have to be careful with it.


So, with the math out of the way, what does it mean? It means that getting the highest signal per sub is best. More specifically (and this involves more complicated math), you want to get your signal strength high enough in each sub that you totally swamp read noise with your "background sky". When you do that, you become photon shot noise limited, and read noise is effectively dealt with by a simple offset (i.e. when you stretch your data, you just shift the black point up, and that reduces the read noise contribution to zero.) Doing this with a DSLR doesn't actually require that you know the math...really, exposing long enough that the histogram for your images peaks at the 1/3rd mark (from the left-hand edge on most cameras and in all software, where the black point is) is generally enough to swamp read noise unless your combining more than a couple hundred frames.


I therefor strongly encourage you guys to get the longest subs you possibly can, before you start getting elongated, eggy, or trailed stars. That generally means exposing for much longer than 1 second, and that requires some kind of tracking mount. But the difference is massive. Even if you go from one second to five or ten seconds (which, without a tracking mount, if you have large enough pixels and/or a short enough focal length, that could be possible), that would be a very significant difference in per-sub SNR, which would result in significantly better integrations.

5
Derp. Seems these are 5-ink "business line" printers, not photographic printers. Canon really needs to separate out their lines of printers better...imagePrograf always makes it sound like these are photographic printers, when not all of them are.


Guess Epson's still at the top of the list...

6
EOS Bodies / Re: Global Shutter Coming to Canon DSLRs? [CR1]
« on: January 22, 2015, 01:24:33 PM »
Would this allow to sync flash at any shutter speed if we have a flash trigger that is quick enough?


There is no reason why not. Would be very interesting if they did...the trend lately seems to have been to reduce the sync speed instead of increase it, which has been disappointing.

7
Wow. I've been looking to get a 24" large format printer for a while. I keep looking at older models of Canon and Epson wide formats....but at less than $1300, the iPF670 is a steal. O_o

8
Animal Kingdom / Re: Show your Bird Portraits
« on: January 19, 2015, 02:29:44 PM »
Excellent shots lately, Jack! You have improved by leaps and bounds since you first started last year. LEAPS and bounds. Your chickadee shots are better than anything I've taken. Love that first in flight one...superb!

9
Landscape / Re: Deep Sky Astrophotography
« on: January 19, 2015, 02:28:10 PM »
Great images, guys! I'm glad to see some of you are getting into astrophotography. :) It's a great hobby, especially if your an insomniac like me. :P


nightclicks, excellent results with M42 there. You managed to pull out some of the faint outer dust, which is really quite a challenge. You must have some decently dark skies to do that.

10
Landscape / Re: Deep Sky Astrophotography
« on: January 12, 2015, 06:21:06 PM »
Yeah, I've been having a lot of problems with DSS comet stacking as well. I found a PDF recently that explained a specific imaging procedure. The guy was imaging with a mono CCD with color filters, so his sequencing was complex. The trick was to use 20-second gaps between frames to ensure that stars were fully separated from each other. That is the only way that DSS will be able to properly apply kappa sigma clipping to reject stars when it registers on the comet. Anything else, and you'll have problems.


I've been integrating with PixInsight, and have had largely the same problem as with DSS. I think the star-gap technique is the right way to image a comet. If I get another change, I'll be employing it.

Ah interesting.  Since I took 130x20sec subs, I can use every other one that passes a decent score and see how that works.  That gives me a 21 second gap between subs.  Surely I can get at least 40 subs still.

So one of the issues I a see with pixinsight comet integration is that it assumes all subs are taken without moving the field of view.  That is you specify where the comet is on the first and last subs and it interpolates the position on every other sub.  I guess you have to do a star align on every sub first to normalize the fov then do comet integration.


Yes, generally that's how comet imaging works. Most things assume that (DSS does for it's default integration, where you only mark the comet in the first and last subs sorted by time index.) If you change the field between subs, then your on your own. :P

11
EOS Bodies / Re: Speculate: How much noise improvement from 5D3 to 5D4?
« on: January 12, 2015, 01:18:23 AM »
Silly topic IMHO. Why people are so obsessed with noise is beyond me. I notice its mainly from amateurs who have never shot film. Everyone wants to shoot at ISO 25600 and want it to look like
ISO 100. I dont get it. Get over it people.


Actually, you have that backwards. We want to shoot at ISO 100 and not have it look like ISO 800. ;P That is the primary issue with Canon sensors...the noise ramps up as you get to LOWER ISO settings. ISO 100 has aroun 1.5-2x more read noise than ISO 200, which in turn has 1.5-2x more read noise than ISO 400, etc. That flattens the DR curve out, WASTING information that the sensor actually gathered and could otherwise be usable.


It's never been about shooting at ISO 25600 and having it look like ISO 100. It's about getting out of ISO 100 what is there to start with. Canon's high frequency, low parallelism, off-die ADC units are throwing away massive amounts of usable information, where as sensors from other brands are preserving 2-8x more information.

12
Landscape / Re: Deep Sky Astrophotography
« on: January 12, 2015, 01:13:36 AM »
Yeah, I've been having a lot of problems with DSS comet stacking as well. I found a PDF recently that explained a specific imaging procedure. The guy was imaging with a mono CCD with color filters, so his sequencing was complex. The trick was to use 20-second gaps between frames to ensure that stars were fully separated from each other. That is the only way that DSS will be able to properly apply kappa sigma clipping to reject stars when it registers on the comet. Anything else, and you'll have problems.


I've been integrating with PixInsight, and have had largely the same problem as with DSS. I think the star-gap technique is the right way to image a comet. If I get another change, I'll be employing it.

13
Landscape / Re: Deep Sky Astrophotography
« on: January 11, 2015, 04:26:11 PM »
Seems that no matter what I do with DSS and the post in PS, this is the best I can get.  By the time I work through the repetative curve process, the background ends up looking like 16 shades of grey.  I know there is nice data here to be had but it's not coming out with the old school tools.

So I just submitted my trial license for pixinsight before I get too discouraged and give up.


PixInsights calibration, registration, and integration tools are far better than DSS. The registration is far superior, and it includes a CometRegistration tool. I recommend following this:


http://harrysastroshed.com/pixinsight/pixinsight%20video%20files/2013%20pix%20vids/cometstack2/cometstack2.mp4

14
EOS Bodies / Re: High Megapixel Camera Coming in 2015 [CR3]
« on: January 11, 2015, 04:19:26 PM »
If that is the case why SONY made a7S? They could stick to a7 and even more to a7R and that's it!


The A7s has more advanced in-camera noise reduction. Exmor is a good sensor, but it wasn't good enough to produce ISO 400k with the low noise levels that the A7s has. The Bionz X DSP is responsible for reducing the noise in each pixel as they are read out. Not much different than what Canon is doing now with DIGIC 6 in the 7D II. If it were not for the more advanced in-camera NR, I would agree...the A7r when downsampled to 12mp would have probably looked very similar to the A7s, primary difference being the downsampled A7r image would be sharper.
So in A7s they... "cook" the raw files?  :o


They do, just as much as Canon "cooks" the RAW files in the 7D II with DIGIC 6. ;P Everyone's cooking pixels today, it's all the rage.
In that case they should be able to "cook"  ;D the A7II files even better since the later camera is newer...


They probably are. The big problem with Sony files is the darn compression. I honestly don't understand that move by Sony, as it wastes so much of the potential of their sensors and their cameras. It doesn't matter to every photo, but enough photos end up with compression artifacts that it's a real bummer. So, regardless of how much Sony cooks their images, I'd say the RAW compression is a vastly more important, and detrimental, issue.

15
EOS Bodies / Re: High Megapixel Camera Coming in 2015 [CR3]
« on: January 11, 2015, 02:26:26 PM »
And in 6 months time, maybe that will be the debate here:

"Canon has more MP, better AF!"
"Sony has more DR, better IQ!"

... but the problem for lots of us will be that a FF sensor that performs the same as the 7D2 sensor won't represent anything new or better: there will be just more of it.

So more DR = better but more MP doesn't? That just betrays your personal preferences. Both can be better, both can be irrelevant, depending on needs.

Quantity (more MP) is not the same as quality (better MP)

You seem to have missed the point of what I said. Better isn't an objective term. For *some* people, having more pixels of even the same quality as today (however you measure it) is better.


+1 I totally agree with this. Not everyone has the same needs. Some people simply need more pixels, others need better pixels. There are certainly options out there if you need better pixels.


It would be nice if you could get both...more AND better pixels...and from Canon (as they do so many other things so well). :P But, that doesn't seem to be in the books...

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