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Messages - jrista

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1621
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 10:05:34 PM »
Full well capacity is really more a function of pixel area than pixel Q.E. Area is the defining factor when it comes to how much charge a pixel can hold. Increasing Q.E. might improve sensitivity, which is the rate at which photons convert to charge, but it doesn't do anything to increase the maximum charge (FWC) a pixel can contain. That is why cameras with larger sensors generally perform better than smaller sensors...they have historically had larger pixels.

No, larger sensors perform better (for a given exposure) because they are, well, larger. Pixel size is a secondary, mostly irrelevant factor.

Correct. I did read, and still remember, the article on equivalence. So, correct, assuming you are always using the full sensor area. There are situations where you don't, say cropping for detail. In which case, the part of my answer you did not quote applies...it's a tradeoff. I am not about to say pixel size is the most important factor, however I would say it is far from a "mostly irrelevant factor." It all just depends, and you make the various tradeoffs you have to in order to get what you need so service your own personal photography best.

In the end, one could often make the argument that neither pixel size nor sensor size really matters in the end anyway, as a more significant factor in final image quality is how you process, so long as the image output size is smaller than the input size (which is by and large the most common case these days with publishing occurring on the internet far more than it occurs in print in any form).

1622
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 09:52:23 PM »
Fairly simple reason for this..... assuming the same technology for reading the charge, if you make the photosite with twice the area, it will collect twice the charge, and the accuracy of the reading will be twice as accurate.....but this is only true until saturation is reached.... and that's why FF is so much better in poor light with less of an advantage in good light.


Wrong, the D800 is as good as the D600. Pixel size is an almost irrelevant factor, sensor size is the main factor (for the same exposure). You are confusing what happens at pixel level with what happens at image level.


Here is my logic......
Let's say that you have two cameras, one with pixels twice the size of the other. We assume a 16 bit a/d converter. We assume that all the circuitry is of the same technology.

You take a picture of the same scene with both cameras. In the first camera there are 0 units of charge in a dark pixel and 500 units of charge in a bright white pixel... Gain is applied (multiply by 128, either digital or analog) and you end up with a 16 bit number where the last 8 bits are noise.
In the second camera there are 0 units of charge in a dark pixel and 1000 units of charge in a bright white pixel... Gain is applied (multiply by 64, either digital or analog) and you end up with a 16 bit number where the last 7 bits are noise.


That is noise per pixel, not per area. The signal in the first case will have weight 1/2 of that in the second in the final image. So you multiply by 128 but when you resize to the final output image, you divide that by 2.


Assuming you resize.

@Don: Pi is referring to Equivalence. He has brought it up in prior threads. The source of the theory is actually very good. Read this: http://josephjamesphotography.com/equivalence/index.htm. It might clear some things up.

1623
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 05:43:55 PM »
Doesn't larger FWC allow more DR?  Of course, as I type this I'm thinking about the D800 its DR.  Ah hell, I'm going back to using the green square mode and not thinking about this crap.

Only really at the lowest ISO setting, however to get more usable DR than the best sensors offer today, you would also need to increase bit depth. The best sensors on the market (Exmor) get around 13.2 stops of DR at the lowest ISO setting. You might be able to push that to 13.8 stops and still use 14 bit data, but to get any meaningful increase, you would need to use full 16 bit data.

Full well capacity is really more a function of pixel area than pixel Q.E. Area is the defining factor when it comes to how much charge a pixel can hold. Increasing Q.E. might improve sensitivity, which is the rate at which photons convert to charge, but it doesn't do anything to increase the maximum charge (FWC) a pixel can contain. That is why cameras with larger sensors generally perform better than smaller sensors...they have historically had larger pixels.

It's a trade-off, though. While those larger pixels have less noise, they also reduce spatial resolution. If you have a FF sensor with 8µm pixels and an APS-C sensor with 4µm pixels, the FF sensor will have a higher FWC and therefor less noise, but also half the resolution.

1624
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 05:28:07 PM »
Okay, since I've been soundly mocked for suggesting a 1-2 stop improvement in ISO performance for a 7DII, I'm a bit stunned.

Is it the consensus of the techies on this forum that is truly impossible for any manufacturer to produce an APS-C sensor in which the noise level at 1,200 ISO is comparable to 400 ISO (a 1.5 stop improvement)? Or, for that matter, that ISO 800 could look as good as ISO 400 (a one stop improvement)?

That doesn't seem like an unrealistic expectation, but apparently it is.

If that is truly the case, then I have to wonder what is the point of any future upgrades? Yes, I understand there is more to a camera than the sensor and even with sensors there is the whole quagmire of dynamic range that I'd rather not get into. But, given some of the real world and highly impressive images I've seen on this forum and elsewhere shot with the 5DIII at, what for me as a former film shooter, are remarkable ISOs (3200, 6400 etc.) it just doesn't seem unreasonable to expect the 7DII to boost its ISO performance by even one stop.

If we are truly at the physical limits of sensor performance and can never get an additional fstop out of any future sensor, what does that mean for the industry? And, as a side note, given that Canon is poised to jump into the surveillance market in a much bigger way, is this a fool's errand if we have reached the limits of low-light performance?


Quantum efficiency (QE) is the fraction of photon flux that contributes to the photocurrent  in  a pixel. Increasing QE improves sensor signal to noise ratio and dynamic range.
There are sensors from Sony who has a QE  of 75% and a pixel size of 1,85 micron, Canon best sensor regarding QE is in S100  compakt camera and QE 52%   ,  6D has the best QE among  Canon SLR  with 50%  compared with  Nikon D800 and 56% QE
The read noise from  Canon are 10 times higher  (6D)  up to 14 times higher (1dx) than in Nikon D800 .
Improving an APS sensor with real 1,5-2 stops in terms of signal /noise is a big challenge and can not be done with Canon's existing sensor technology regarding APS and 24x36mm sensors

Agreed....to get a visible improvement in high ISO noise performance on an APS-C sensor, Canon is going to have to improve their sensor technology. They will also need to improve their ADC technology as well, though, as a lot of read noise in Canon's current technology actually comes from downstream sources. Those downstream sources seem to cause worse read noise at lower ISO than at higher, but Canon's Q.E. has been improving at a snails pace, and without a significant jump, it is doubtful anyone will see any drastic improvement at higher ISO settings. Given that the 7D II is currently rumored to use a DIGIC 5+, it seems doubtful that Canon has changed any significant aspects of their design...the DIGIC chips currently house their ADCs, so it is most likely that the 7D II will just have two higher stops of even noiser high ISO, rather than an improvement in ISO 3200 by a stop or two.

1625
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 05:22:57 PM »
The new spec looks tempting.  Maybe I should consider selling my current one...

I wouldn't sell until the date they will hit the shelves is known. If Canon's past camera releases are any indication, the actual arrival of any new Canon DSLR is somewhat like the return of Jesus Christ...unknown, unknowable and like a thief in the night. ;)

1626
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 05:20:49 PM »
I don't want to get stills from video but I also don't know why I should accept poorer frames for video than I do for stills.

...
even with a 50inch 4k display you will hardly see a difference from normal viewing distances.
the human eye is not able to resolve that good.
...

Erm, this is so completely wrong. It entirely depends on your visual acuity. The whole notion of the "average" person having 20/20 vision implies that a certain percentage of people also have better vision (and some much better), and that a similar percentage of people have worse vision (and some much worse). For the people who have worse vision, corrective optics these days EASILY correct vision beyond the 20/20 mark. Personally, I am slightly near sighted, and with my contacts or glasses, I have 20/10 vision, like so many other people with corrective lenses. (At my eye doctors office, they generally purposefully try to find the absolute best correction possible, aiming for the highest visual acuity possible. They see thousands of people a year, so you have to figure that between people with excellent vision, people who are slightly far sighted, and everyone walking around with corrective lenses...the "average" visual acuity is actually higher than 20/20.) 

I currently have a trusty old Samsung 46" 1080p TV, and I can just barely see pixels when sitting from the TV at a "comfortable" distance. The distance is ideal for my room setup, with the TV at the recommended distance from my couch. There is no question that bumping the resolution up to 4k would do wonders for quality. It is just simply not enough to have pixels just on the border of 20/10 visual acuity (which is what's recommended)...you need to have the pixels be much smaller in order for them to NEVER intrude on your experience.

Same thing goes for using higher resolution computer screens. Even sitting an appropriate, comfortable distance from my 30" 2560x1600 screen, which until 4k displays started arriving had one of the smallest desktop pixel pitches, exhibits this slight pixellation effect. I can't exactly see individual pixels, but they are again just on the border of my visual acuity...so they bug me. A 4k 32" display would almost reduce the pixel pitch in half, and do wonders for microcontrast and allow me to see fine detail in my photos as fine detail, rather than fine pixels that contain detail I should be able to see. Furthermore, if you print, you'll know that it is extremely difficult to soft proof a print on a screen that has at least 1/3rd the pixel density of the print. You can never really tell how the detail will turn out in a print. Personally, I'd be ecstatic with a 28" screen that had a 300ppi pixel density. I'd be able to properly soft-proof the majority of my larger prints at a directly comparable resolution.

There is a LOT going for 4k screens, both TVs as well as workstation screens. The human eye absolutely can resolve that well unless you have particularly poor vision or just have average vision and don't use corrective lenses. Same as with sensor pixel densities, however...the actual output resolution of any system is effectively approximated by the RMS of the individual components. Increase the resolution of a screen, and the ultimate resolution of what your mind's eye sees will still improve, even if you have only 20/20 vision.

1627
EOS Bodies / Re: EOS 7D Mark II Spec List Surfaces [CR1]
« on: October 30, 2013, 05:03:27 PM »
I can't help thinking that with declining sales across the board there are too many cameras and too little real innovation in most manufacturers' line-ups. Perhaps it would be a good idea to make the 7D MkII the last conventional DSLR (at least in the APS-C range) and move towards a future without mirrors.

Good grief.  EVFs are years, if not decades away from being usable in high-speed and/or low-light situations, plus we need a good factor of 4 increase in battery performance before we go that way.

Totally agree. I'll never use anything but an OVF for my wildlife and bird photography...unless they somehow do manage to create an EVF with 10,000 ppi, 20 stops DR, and a 60fps refresh rate (something I doubt will happen any time soon...)

1628
Macro / Re: Denizens of the Forest Floor
« on: October 03, 2013, 03:34:07 PM »
No idea what this one is.  Take in ards a forest park, Donegal with 600d and 50mm 1.8. 

Mushroom by andersde, on Flickr


Great shot. I get gigantic colonies of something similar in this one corner of my yard each year. I mean, colonies of maybe fifty individual mushrooms, but clumped together such that they form this single fungal mass that is often FEET in diameter.

Love that carpet of moss, too!

1629
Macro / Re: Denizens of the Forest Floor
« on: October 01, 2013, 03:14:39 AM »
the tastiest of them all!

Love morels! Great photo, too!

1630
EOS Bodies / Re: 7DmkII F8 AF for wildlife?
« on: October 01, 2013, 03:13:49 AM »

I've used the Kenko with the EF 600mm f/4 L II, and its performance is stellar. Focus is pretty fast (although I believe the primary limiting factor here is actually the 7D, I hope a 5D III will be faster), and it is pretty accurate. Precision is good. CA definitely increases with the Kenko, and depending on the light and atmospherics, IQ can suffer to an undesirable degree.


A TC costs only a few percent of the price of the 600/4 II. The Canon Mk III TC is specifically designed to dovetail with the II series lenses. Have you tried it?

I own both the EF 1.4x and 2x TC IIIs. Both are superb (although I am relegated to manual focus with the 2x until I can afford a 5D III.) The primary improvement is corner performance. The 1.4x TC II is only barely better than the Kenko. The 1.4x TC III has a definite improvement in corner performance and CA handling. Center performance is pretty similar between the Canon and Kenko 1.4x TCs.

1631
EOS Bodies / Re: 7DmkII F8 AF for wildlife?
« on: October 01, 2013, 01:12:14 AM »
I had no trouble with f/8 AF on my 7D, my 40D, or even my old 10D when using a Kenko DGX TC and my 100-400mml.  There is a incompatibility with a 100L, but AF works well with the Kenko.  No need to worry or wait if you need it, its been here for a long time.

I also have the Kenko DGX. I purchased it for the explicit purpose of using it with the 100-400mm. It works, but only in stellar light. During the times of day I needed it most, mornings and afternoons just after and just before sunset, it pretty much did not work at all. It is really a mixed bag when you do f/8 AF on a camera body that does not officially support it. When it does work, it is very slow. Hunting occurs frequently. When I have great direct sunlight, it will usually work, but I've also noticed that it lacks precision...when it "locks", focus is usually off just a little bit. It is random, whether it focuses front or back, so the 7D AFMA is not helpful when using it. Further, CA and IQ become very problematic when using the Kenko with the 100-400.

I've used the Kenko with the EF 600mm f/4 L II, and its performance is stellar. Focus is pretty fast (although I believe the primary limiting factor here is actually the 7D, I hope a 5D III will be faster), and it is pretty accurate. Precision is good. CA definitely increases with the Kenko, and depending on the light and atmospherics, IQ can suffer to an undesirable degree.

It is a good TC, but I would not go so far as to say that you'll get flawless or even great f/8 AF performance out of it on a body that does not officially support f/8 AF. You might get some good performance at some times with the right kind of light, and at other times you may get nothing but full-range hunting and zero focus locks.

1632
EOS Bodies / Re: 7DmkII F8 AF for wildlife?
« on: October 01, 2013, 01:07:38 AM »
Individual faces of birds... wow!  ;D

I recall reading that someone mentioned the 1D X face detection during phase AF worked for owl faces...

That was Andy Rouse, and he had a number of shots to demonstrate it.

1633
Macro / Re: Denizens of the Forest Floor
« on: September 30, 2013, 06:46:49 PM »
Growing on a fallen tree

I like the perspective on these.

1634
Landscape / Re: Waterscapes
« on: September 30, 2013, 06:46:17 PM »
Great shots, everyone! Beautiful scenes.

1635
EOS Bodies / Re: 7DmkII F8 AF for wildlife?
« on: September 30, 2013, 06:45:37 PM »
If the Dual Pixel CMOS AF is fast and accurate enough, that works out to f/11 (although I'm skeptical of accuracy at narrow max apertures).

For wildlife, I would have additional concerns as well. How does tracking perform when you are rapidly panning? How is tracking consistency? For that matter, how is the consistency overall, even at f/5.6? With video, you have a continuous stream of frames at high speed that the DPAF firmware can use to provide more accuracy, something you don't really have with wildlife or bird or sports photography.

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