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Messages - sarangiman

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1
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: September 02, 2014, 08:52:58 PM »
There's another arena Canon may do better in w/ the 5D3/1Dx AF module. There are 5 high-precision dual-cross-type sensors down the middle. I wonder if these actually have demonstrably higher precision for wide aperture shooting compared to Nikon's central AF points. To my knowledge, no one's tested this rigorously.

I've also noticed some body/lens combos where there'd by systematic back/front-focus based on which direction the focus element was moving. With both Canon and Nikon systems. I wish someone would test this stuff in a systematic manner so we could see where these problems do or do not exist.

Ultimately, though, the inability to track subjects in the X-Y plane have led to many more missed shots with my 5D3 compared to (my limited shooting thus far with) the D810, so that matters to me.

2
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: September 02, 2014, 08:40:26 PM »
Don's post reminds me: Canon's Dual-Pixel AF is one of the most exciting technologies I've seen recently. If this tech grows and is implemented correctly, it could really revolutionize AF, in my opinion. It could probably do away with AF microadjustment, while increasing precision of wide aperture/shallow-DOF shots. On-sensor PDAF will have to find a way around the low SNR of split photodiodes or masked pixels, but there are some obvious ways around this.

I do hope Canon invests in this tech.

3
Third Party Manufacturers / Re: D810 users are seeing spots
« on: September 02, 2014, 08:36:13 PM »
I'm still trying to find a sunset where some some subject in the scene hits the noise floor of the D810 at ISO 64. I just can't. I need one of those special spectacular sunsets that happen like once a year where the clouds light up half an hour after sunset.

I had similar trouble with a Pentax 645z at ISO 100. These sensors are incredible.

Remember: shadow SNR is still limited by shot/photon noise. Only extending FWC or sensor size will help here.

4
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: September 02, 2014, 08:30:30 PM »
Oh, and jrista:

I meant to respond to your comment at some point about how you shoot at ISO 400 and average images to help with Canon DR. Honestly, at first glance I thought it was quite funny, but I did the math and you were on to something there. I'll see if I can write out the actual math to show where that method benefits, and where it doesn't.

But in the meantime, I just wanted to say:

Some people will say that extra DR doesn't help landscape photographers that much b/c the shot noise in the shadows makes shadows look like higher ISO shots. So you should HDR anyway. Ok, valid point; just that with Canon you have this problem *on top of* extra noise due to read noise.

But I'd argue that even in such situations, the higher DR sensor still helps dramatically. Why? B/c you don't actually have to merge different exposures to get HDR. You can just shoot a bunch of the *same* exposures - since almost everything is more likely to be above the incredibly low noise floor - then average them, then post-process to taste. This avoids the issue of masking/HDR software merging different exposures, where dark/bright boundaries can cause issues in the algorithms as to which image to use pixels from. Of course, you may still have to mask for selective brightening/darkening, but this is much easier - to me anyway - than merging different exposures for HDR.

With Canon & this method, you'd be fighting read noise on top of shot noise, requiring you to average many more images. Or increase the exposure to get some of the darkest subjects in your scene above the noise floor to begin with.

Make sense?

5
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: September 02, 2014, 08:20:21 PM »
Are there any reasons why you wouldn't buy Nikon? Aside from their awesome DR...there are a number of reasons why they are not as good an option as Canon. I've listed them so many times now, I'm not going to again...however, I'm sure your reasons are the same as mine for preferring Canon.

Your statement embodies the core frustration with Canon, though. Why the hell am I shooting Canon when there are other brands with more resolution?

My question is: Why can't I have it all in a single brand? Why does everyone find it so "odd" that someone wants that? :-\

We share the same sentiment here. Camera companies are far too slow to innovate and disrupt. Sony is at least trying, at least partially, if not mostly, because they literally *have* to in order to make a dent in the market.

That's at least partially why we can't have everything in one camera.

And I don't know that you can particularly blame them. The market itself looks like it's shrinking. And companies need to do what they need to do to survive. That said, from a consumer perspective, I can't help but be pleased when I see companies innovate for their customer base.

But a bigger reason - IMHO - is b/c they really can't predict all use-cases. And ideas propagate slowly within complex organizations. Which is why, eventually, whoever opens up their cameras and crowd-sources function/app-development will have a huge impact in this regard. I think, anyway.

Are there any reasons why I wouldn't buy Nikon? Not any compelling ones anymore. I guess I'd say:
  • Lack of non-central cross-type AF points
  • The wireless flash system w/ the 600EX-RT
  • That wonderful new Canon 16-35 f/4L IS (I'm sure hoping that Sigma 14-24 rumor is true; I don't like the ergonomics of the Nikon 14-24 that makes practical use of filters impossible)

Ultimately, though, those aren't compelling enough to overcome the poor DR, FPN, banding, lower resolution, and utter lack of any reasonable AF tracking capabilities in 3D (meaning, the X-Y 2D plane as well as the depth axis).

And before someone brings up how the DR evens out at high ISO - no it doesn't, not if you shoot in an 'ISO-less' manner where you can maintain somewhere near the full base ISO DR at higher ISOs simply by not allowing your ISO to float (assuming quantization error does not become a factor). But that's far too much to get into here. Incidentally, this type of shooting is exactly what you hounded me for doing when you de-railed that thread years ago where I compared the D800 to the 5DIII. About underexposing 5 stops & then pushing in post. Funny enough - that's exactly what I do right now in certain situations with my A7R in certain high DR scenes where I'm light limited b/c of the shutter speeds and/or aperture I wish to use. And it's likely to be the way cameras work in the future. Again, too much to get into here, but I'm guessing you know exactly what I'm referring to. As I said in my follow-up comment years later on that thread - underexposing 5 stops is nothing for some sensors these days. The only noise cost you pay is a tiny bit of quantization error (that's probably irrelevant) and mostly just the shot noise cost you'd pay anyway if you shot ISO 3200 (5 stops less exposure than ISO 100). Anyway.

Let me address that comment about AF tracking I made above. To be frank: I wish I'd tested Nikon's 3D AF tracking a long time ago. I use it in a bit of an unintuitive way - to avoid the focus issues arising from focus & recompose changing your plane of focus. Instead of moving the AF point using the antiquated joystick/D-pad method (far too slow), I let the camera automatically track the subject I initiate focus on using the center AF point. The only Canon camera that can even attempt this is the 1Dx, and even then it doesn't do it as well (in my tests) as the Nikon D800/D810/D4s - presumably b/c Nikon's been honing this for years. And then I have the added benefit that if the subject does happen to move while I recompose, the camera takes care of that as well. This did wonders for my baby photography, actually. I nailed shots focused on the eye of a wildly moving baby at f/1.4 - something I couldn't have dreamt of doing with my 5D3. Unless I stuck with a static AF point, of course, and manually recomposed to follow the eye/baby around such that the AF point was always over the subject of interest. 3D AF tracking obviates the need for this - allowing you to uncouple focus from the composition.

That's huge, to me.

It literally opens up shooting possibilities for wedding photography that no Canon camera - save for the 1Dx - can even dream to attempt.

And the same hardware that enables this allows for spot-metering all over the frame, and face-detection metering. Again, only the 1Dx can attempt this, but many Nikon cameras do this with either their 2k or 91k pixel RGB sensor. Even the D7000 tracks across the frame surprisingly well, with its limited resolution (2k) RGB sensor. The 91k pixel sensors do it better, but it's admirable that a camera like the D5300 can even do this at all. Compare that to a Rebel that can't even attempt to, and even if it could, it'd be of limited utility with 9 AF points.

I've shot Canon since the film era, including the 5D, 5D2, and 5D3. And I can honestly tell you that for my type of shooting, switching to the Sony A7 series and the D810 has opened up shot opportunities for me that I just couldn't imagine with my Canon cameras.

YMMV.

6
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: September 02, 2014, 07:27:12 PM »
I want as much resolution and dynamic range as I can get my hands on, particularly for landscapes.

And yet you shoot Canon...  ???

Just FYI - initial data suggest the dynamic range of the Nikon D810 at ISO 64 approaches that of the medium format Sony sensor inside the Pentax 645z (amongst others) at ISO 100.

7
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: August 29, 2014, 04:53:22 PM »

And Sony? Compare the the 36 MP Alpha A7r(esolution) and the 12 MP A7s(ensitivity), then say again that more MP does not mean more noise if you dare. At base ISO maybe, but try going at 800 and beyond...

I'll take your ISO 800 and beyond and raise you a comparison between the A7r and A7s at ISO 3200:

http://www.dpreview.com/reviews/image-comparison/fullscreen?attr65_0=sony_a7s&attr65_1=sony_a7r&attr66_0=3200&attr66_1=3200&attr67_0=raw&attr67_1=raw&attr68=12mp&normalization=full&widget=119&x=0.15845192244437983&y=0.31115156636410585.

See any difference between the two when normalized to 12MP? I don't think so. Everything was controlled in this test, down to using the same exact lens, same shutter speed, aperture, ISO, etc.

In fact, I don't see any appreciable advantage over the A7R until you hit ISOs of 25.6k and beyond. Because at that point, the crumbs start encroaching on the slices, in the pizza analogy. For deep deep shadows, the A7S' takes over at ISOs of 6400 and beyond. Really depends on the tone you're looking at, b/c different tones are affected differently by the different sources of noise (shot noise, read noise, etc.).

But ISO 800? 1600? You're unlikely to see any appreciable difference.

LTRLI also made an interesting point about finer-grained noise of higher resolution sensors. So there's also that to consider.

8
EOS Bodies / Re: EOS 7D Mark II & Photokina
« on: August 29, 2014, 01:11:21 AM »

Also, since smaller pixels hold less charge, the chance of blowing highlights is higher than a larger pixel sensor.

But for the same focal plane exposure, the smaller pixels also receive less light because, well, they're smaller. So total sensor DR does not necessarily have to suffer for higher resolution sensors.

   As a result, sensors with larger pixel have better dynamic range than sensors with smaller pixel even if the total sensor size is the same.
 

If all else is held the same, yes. In reality, this doesn't generally always turn out to be true. For one, sometimes manufacturers are able to decrease per-pixel read noise with the smaller pixels of the higher resolution (but same size) sensor. For a sensor of n times higher resolution, all you have to do is decrease per-pixel read noise by a factor of sqrt(n) to achieve equivalent normalized noise performance.

This may be why the Sony A7R has just as much DR as the A7S, and normalized noise performance is similar. But, admittedly, I'm just guessing here.

The point is, there are a number of variables here one must consider. It's not always straightforward. For example, the A7S with its 12MP has demonstrably lower DR in RAW than the A7R with 3x as many pixels. Probably resulting from increased downstream read noise of the architecture.


Nope. I haven't forgotten noise or SNR. The 5µm pixels will have twice the noise. However, a 2x2 matrix of 5µm pixels equal one 10µm pixel in terms of area. Average those four pixels together, and you reduce noise by SQRT(4), which is? Yup. A factor of two. The 10µm pixels have four times the area, which again, reduces noise by SQRT(4), or a factor of two. There is more noise per pixel, however the noise per absolute area of the subject is the same. The sensor with smaller pixels has twice the image dimensions. Downsample the 4460x2980 pixel image to 2230x1490...and there will be no difference in noise.

The only difference you WILL see? The downsampled image is SHARPER!  8)

Have a nice day.

No, jrista, the noise per absolute area is not the same. It's pretty close, but it's still worse. It'll only be the same if the n-times higher resolution sensor has its pixel-level read noise reduced by a factor of sqrt(n) compared to the lower resolution sensor. Let's take the case of a 10µm x 10µm pixel, vs. this pixel divided up into four 5µm x 5µm pixels. Let's do some math:

For a 10µm pixel that receives 200 photons, QE=50%:
  • Signal = 100 (50% of 200 = 100 electrons)
  • Read noise=2
  • Shot noise = sqrt(100) = 10
  • Total noise = sqrt (10^2 + 2^2) = 10.198 [yes, this is an approximation, but it'll suffice]
  • Per-pixel SNR = 100/10.198 = 9.806

For the four 5µm pixels that also receive a total of 200 photons, or 50 photons each, QE=50%:
  • Signal = 25 (50% of 50 = 25 electrons)
  • Read noise = 2
  • Shot noise = sqrt(25) = 5
  • Total noise = sqrt (5^2 + 2^2) = 5.385
  • Per-pixel SNR = 25/5.385 = 4.6424
  • After averaging those 4 pixels, SNR increases by sqrt(4)=2, so SNR for that area is now 9.285
  • Another way of determining the SNR of the four averaged pixels is to calculate out the noise: total noise after averaging will be sqrt(4*sqrt(29)^2) = sqrt(116) which you can already tell is going to be more than sqrt(104), the total noise of the 10µm pixel. But let's continue: sqrt(116) = 10.77. Adding together the signal of the 4 pixels gives you a signal of 100. So SNR = 100/10.77 = 9.285.

Point is, SNR of 9.8 > SNR of 9.3. This is generally a bit academic of a difference, which is why high resolution sensors generally do so well. But for extremely high ISOs, where you have so little signal to begin with, it can make a difference. Or when the higher resolution sensor has many, many more pixels.

The take-home point is that when you average the smaller pixels of a n-times higher resolution sensor, you completely equalize shot-noise performance per-area. But not read noise performance. Why? Simply b/c you have n times as many read events.

9
Third Party Manufacturers / Re: Nikon D810 Product Advisory
« on: August 21, 2014, 02:41:31 PM »
most of what this D810 has over the D800E actually done with FW updates, which Nikon seldom does.

Like the redesigned mirror & shutter mechanism, the complete lack of OLPF, faster processor, and true ISO 64 along with the shot noise and DR benefits it can bring?

Quote
And for high resolution required work, we do not need or want the mirrorslap anyway, and thus the A7R would be much better choice for most of us.

Nikon is seriously doomed.

That's ironic, b/c the A7R's shutter shock is literally unavoidable (at longer focal lengths), while the D810 at least offers an option for an electronic 1st curtain that - when combined with mirror up+delay - can completely get rid of camera-induced shake. So, despite Nikon's poor implementation of electronic 1st curtain (only available in Mirror Up mode), at least it offers a way to completely eliminate shutter shock. The only way to mitigate it on the A7R is to add a ton of mass to your camera (which kind of defeats the whole point of the little FF wonder), and even then you may or may not completely eliminate it.

10
Third Party Manufacturers / Re: D810 users are seeing spots
« on: August 21, 2014, 05:35:10 AM »
They don't learn quickly: back in the day, when I shot Nikon, a solution to the D200's horrible banding problem had to be dragged, kicking and screaming, out of the buggers - and it never did really fix it (for me anyway) on either of my D200s.

That camera is why I'm a Canon shooter now.

Having issues with banding, and then being satisfied by switching to Canon... now there's something I'm going to have to scratch my head over for a bit.  :o

11
EOS Bodies / Re: Exmor vs DualISO
« on: August 18, 2014, 12:18:06 AM »
Intresting. Thanks for your effort. Therefore, ML would also provide to high ISO nightshots?

No, ML Dual ISO will not help with high ISO performance. Dual ISO simply helps to deal with the noise resulting from the architecture I mentioned earlier. The 'downstream' read noise this architecture is well known for - and what dual ISO helps to avoid - becomes pretty irrelevant at high ISOs. It's swamped by other sources of noise - namely shot/photon noise and 'upstream' read noise. Shot noise contributions are determined by how much light is collected, so roughly correlates with sensor size & QE. Nothing ML can do here. Upstream read noise for these Canon sensors is already quite good (especially for the 1Dx), and difficult to do anything about without actual hardware-level adjustments. So there's really nothing for ML to do here either.

12
EOS Bodies / Re: Exmor vs DualISO
« on: August 18, 2014, 12:17:51 AM »
Yeah, exactly what raptor3x said. You can probably safely assume a similar benefit across most Canon DSLRs.

Those guys at ML are magicians, I have to say. Personally, I think it's much easier to just go for a Nikon D810 if you care about base ISO DR, especially as the D810 offers yet another 2/3 EV or so DR over the D800/A7 cameras. But if you have other constraints that force you to stick with Canon, this ML trick seems very useful. As others mentioned, the resolution tradeoff doesn't seem as severe as one might expect it to be.

13
EOS Bodies / Re: Exmor vs DualISO
« on: August 17, 2014, 08:19:47 PM »

Speaking of landscapes...high end professional landscape work is not produced by pushing Exmor shadows 4-5 stops. Landscape photographers bracket and HDR. Compare a HDR image to a heavily pushed image, even from Exmor, and the difference in tonality and fine detail will jump off the print at you. With AEB you can easily hand hold a 3 frame bracket.


Good point. And it's because of a subtle point. It's b/c even Exmor shadows are limited by shot noise - noise that comes from the inherent randomness of non-coherent light. This source of noise has increasing contributions with shorter exposures, even for an 'ideal' sensor (which the Exmor architectures are approaching).

You can think of it this way - if a landscape photographer won't use ISO 800, he/she similarly won't push a base ISO 100 camera's shadows 3 stops. Since it's essentially the same thing (ignoring quantization error).

Quote
All that said...I do find it puzzling that Canon went through the effort to make this possible in the sensor hardware but then never exploited it in the firmware. Are they afraid that it might be confusing to users, especially with the HTP mode option? Just add an Extended Dynamic Range (EDR) mode for RAW only and clearly state it's for pro users who are going to manipulate the tone curve in RAW.

Canon didn't go through the effort to make this possible in the sensor hardware. ML just found a way around the limitations of Canon's architecture, which pipes analog data off the imaging sensor to an off-sensor digitizing chip (ADC). This process introduces a lot of noise into the signal, which can be mitigated by pre-amplifying the image data (ISO amplification - raising the ISO) before sending it off the imaging chip. That's why Canon's architecture doesn't hurt its high ISO performance much, but severely limits its low ISO performance.

14
EOS Bodies / Re: Exmor vs DualISO
« on: August 17, 2014, 08:15:05 PM »
What makes you think they haven't used this in the 1DX?  ;)

Because the 1Dx doesn't have much more DR than a 5DIII... and shows the typical pattern of increased total input-referred read noise with decreasing ISO.

15
EOS Bodies / Re: Exmor vs DualISO
« on: August 15, 2014, 05:14:50 AM »
Nice work! Essentially, Magic Lantern is able to recover closer to the 'sensor DR' - by mitigating the effects of downstream read noise probably introduced en route to the off-imaging-chip ADC in Canon architectures.

The extra 0.8EV 'highlight headroom' (or sorts) is interesting. Makes me wonder if something similar is going on with the Nikon D810 & the 36MP sensor in there. DxO data suggest they're able to map a higher signal off the imaging chip to the same Raw value at ISO 64 -- essentially like extending the effective full-well capacity of pixels at this ISO.

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