Canon EOS 7D Master thread

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Archive 2009 · Canon EOS 7D Master thread

alundeb
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p.128 #1 · Canon EOS 7D Master thread

The camera also uses this information in its AF processing too, using it to adjust "for any CA in the AF system" (says Canon) to improve AF accuracy in (for example) artificial lighting, so it's clearly making a lot of use of this apparent ability to recognise different kinds of light...

At least, they have made dynamic color gain adjustment possible.

About the green channel imbalance, I believe theSuede has solved that mystery now by proving different spectral responses. Bravo!

Again, that triggered my thought, and I found in one of my mean-variance measurements: Heck, the two green channels are balanced in this one, they have the same mean and the same variance. I cannot by now find any other explanation other than a dynamic system gain. This is a bit difficult to explain, but the ratio between mean and variance doesn't change for different exposure and color alone. It is closely linked to the ratio of collected photons per raw unit, or the system gain.

Oct 11, 2009 at 08:09 PM

alundeb
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p.128 #2 · Canon EOS 7D Master thread

jorkata wrote:

For my needs, 12mp is a good enough resolution.

So, I’d rather see that manufacturers maximize the S/R ratio for 12mp – rather than giving me more resolution (which I don’t need) with worse pixel level noise (which I don’t like) and telling me that I can downsample and I’ll be fine (which I find arrogant).

I’m a customer. The customer is always right and if they want to sell me something, they'd better make what I'd buy.

I'm a customer too. I bought the 7D because it has 18MP. I would not have if it was 12.
What is most arrogant, to tell you to downsample, or to oversee my needs completely?

Oct 11, 2009 at 08:16 PM

jorkata
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p.128 #3 · Canon EOS 7D Master thread

Agree completely.

That's why in my previous posts I'm suggesting that Canon should make the 7D in two flavors - one with lots of megapixels for those who like that, and another one will less megapixels and better ISO.

Let buyers decide what works best for them (and not argue what works better for the others).

Canon will have the same problem if they decide to push the 5D resolution beyond 30mp.
Not all FF buyers will be happy with that for sure.

Oct 11, 2009 at 08:23 PM

susi
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p.128 #4 · Canon EOS 7D Master thread

Canon is not Burger King...

Oct 11, 2009 at 08:43 PM

bobbyz
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p.128 #5 · Canon EOS 7D Master thread

Guys rookie question, how much better (compared to old 1dmk2) can I expect the high ISO performance of this 7D? What if I throw 40d into the picture also.

Currently I have 1dmk2 and need another body. It is either 40d with 17-55mm f2.8 IS or just the bare 7d. If 7d can come close to my 1dmk2 as far as AF is concerned, I will be very happy. Looking at higher ISO performance also as shooting football at ISO3200 is not that good with my 1dmk2.

Thanks.

Oct 11, 2009 at 08:46 PM

UCSB
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p.128 #6 · Canon EOS 7D Master thread

susi wrote:
Canon is not Burger King...

Very funny ....

Oct 11, 2009 at 08:55 PM

ejmartin
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p.128 #7 · Canon EOS 7D Master thread

keithreeder wrote:

The 7D has a "completely new" dual-layer exposure meter which recognises different colours of light (one layer sensitive to red/green, the other layer sensitive to blue/green) and adjusts the exposure to account for the proportions of these different spectra it receives - I wonder if what you describe is a function of that?

(And - thinking about it - I wonder if this dual-layer meter might account for the apparent imbalance in the green channels?)

The metering system simply suggests an overall exposure time and f/ratio; it does not go and tune the exposure of individual pixels/columns/color planes.

If true, the difference is due to a use of different spectral transmissivity for the two "Green" locations in the Bayer array. IIRC (though perhaps I do not) Canon did something like this in some early P&S models, using a CRGB color filter array (ie one of the Green locations was replaced by Cyan).

Oct 11, 2009 at 08:55 PM

jorkata
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p.128 #8 · Canon EOS 7D Master thread

bobbyz wrote:
Guys rookie question, how much better (compared to old 1dmk2) can I expect the high ISO performance of this 7D?

ISO 800 comparison from a thread on DPreview:

This image is copyrighted by the owner

Edited on Oct 11, 2009 at 09:02 PM · View previous versions

Oct 11, 2009 at 09:01 PM

keithreeder
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p.128 #9 · Canon EOS 7D Master thread

Fair enough, Emil - just putting it out there...

Oct 11, 2009 at 09:01 PM

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p.128 #10 · Canon EOS 7D Master thread

jorkata wrote:
That's why in my previous posts I'm suggesting that Canon should make the 7D in two flavors - one with lots of megapixels for those who like that, and another one will less megapixels and better ISO.

Like I said, you still don't understand this issue at all. "Better ISO", as you call it, isn't brought about by marginal reductions in pixel numbers.

If you took the G11 sensor and extended it to full-frame it would contain 292 Mpixels. A 100 Mpixel full-frame sensor wouldn't necessarily have worse low light performance than the 7D, but it would have latitude more like a very good point+shoot.

4-to-1 pixel binning would make possible a 40 megapixel camera with very crisp 10 megapixel sraw files for those who don't always want big files.

Edited on Oct 11, 2009 at 09:45 PM · View previous versions

Oct 11, 2009 at 09:28 PM

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p.128 #11 · Canon EOS 7D Master thread

jorkata wrote:
I'm suggesting that Canon should make the 7D in two flavors - one with lots of megapixels for those who like that, and another one will less megapixels and better ISO.

They do, it's called MRAW.

Oct 11, 2009 at 09:32 PM

keithreeder
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p.128 #12 · Canon EOS 7D Master thread

jorkata wrote:

ISO 800 comparison from a thread on DPreview:

A thread about 800 ISO which just happens to favour the 1D as a response to a question about high ISO performance?

You just can't help yourself, can you?

And - as responses in that thread clearly spell out - it's an unfair comparison anyway.

Enough. It's the Kill File for you.

Bobby, the 40D is the best part of a stop better than the 1D2n at high ISO and from what I can see the 7D approaches another stop over the 40D - plenty of posts to that effect, and posts like this tend to support it:

http://forums.dpreview.com/forums/read.asp?forum=1019&message=33312385

And the 40D would be hard-pushed to do this:

http://rolandlim.wordpress.com/2009/10/08/canon-eos-7d-iso-6400-test-shots/

Just so you know where I'm coming from, I own and really like the 40D, and have used a 1D2n a fair bit, and have a pal who has provided me with a good few high ISO 1D2n files from when I was looking to buy one.

And I will be having a 7D: high ISO performance is a big part of the reason why.

Edited on Oct 11, 2009 at 09:47 PM · View previous versions

Oct 11, 2009 at 09:44 PM

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p.128 #13 · Canon EOS 7D Master thread

Okies, redid the ADU/Sdev plots - without pixel-doubling... :-) Results are fairly consistent with my first thoughts, but I'm having trouble with my testshots. I can't redo them right now (since it isn't my camera! :-) ) - but I shot the charts/ISO-ranges too well focused. Not very often that you hear those words and "Canon" in the same sentence, huh...? :-) I didn't want the border of the patches blurring too far into the patches themselves (as colour was my main concern), so I aimed focus on the front table-edge - the charts were placed around 70cm back in the inspection cubicle. Light was D50-filtered Halogen, btw.

Either that, or there was some sort of dust/specks gathering on the CC24 - I'm getting slightly too incisistent Sdevs. Anyways, here are the results - first up, Sdev compared to ADU level. One channel is very much more efficient than the other, around 1.6 times according to my (poor accuracy) readings. Error margin +/-10%!

This image is copyrighted by the owner

And then, as per request, the scatterplot of the (Green1-Green2) vs Red/GreenAverage saturation following Emils suggestion of a simple
[ (Gr1-Gr2)/GrAverage vs (Gi-R)*(Gi+R) ] to get the correlation between Red channel saturation compared to average green and green channel difference signal.
Same for blue channel saturation.
There's a strong correlation, the only thing messing things up is the fact that the red channel swings back in efficiency as you get colser to the other end of the spectrum, near blue-violet. Therefore, the blue channel (which is a single peak, no swingbacks or plateaus) shows a much stronger correlation. In fact, a VERY strong correlation.

This image is copyrighted by the owner

So, there's very strong evidence that:
1) the two green channels are not the same efficiency (one has a "diluted" colour filter) and:
2) one green channel is significantly more yellow than the other.

Not of interest to most people I guess, but some of us really want to know the "why" in some of these things...

Oct 11, 2009 at 09:45 PM

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p.128 #14 · Canon EOS 7D Master thread

Can someone with a 7D post comparative shots with RAW,sRAW,mRAW at 100% and at same size. Perhaps something with shadows at a few different ISO (200,800,3200).

I'm interested in general sharpness and noise. Is that asking too much?

Thanks in advance.

Oct 11, 2009 at 09:55 PM

jorkata
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p.128 #15 · Canon EOS 7D Master thread

brainiac wrote:
Like I said, you still don't understand this issue at all.

Here's a quote from you essay:

Is there a downside to jamming in more sensels?
Yes - probably: the smaller a well, the fewer photons it takes to saturate it.

So, let me put it straight to you:

I want a 1.6x sensor with larger wells than the 7D, that saturate with more photons.
I repeat, larger wells is what I'm after.

If this requires the number of megapixels to be reduced copmpared to the 7D, I'll happily accept it - as long as the megapixels count is not too low.

In fact, 12mp with larger wells is what I'd like and pay for.
The current 7D performance (as well as image downsizing) does not work for me.

I'm glad that it works for you, guys, and totally respect your decision to buy the 7D.

Peace

Oct 11, 2009 at 10:00 PM

abqnmusa
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p.128 #16 · Canon EOS 7D Master thread

how about a break from pixelology charts and ANALysis?

lighting was bright New Mexico sky

7D photography ....

full size images are here

2012 © abqnmusa

Canon EOS 7D 400 mm f/8.0 1/750 sec 250 ISO +0.5 EV

2012 © abqnmusa

Canon EOS 7D 400 mm f/5.6 1/1500 sec 250 ISO +1.0 EV

Edited on Oct 11, 2009 at 11:24 PM · View previous versions

Oct 11, 2009 at 10:14 PM

abqnmusa
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p.128 #17 · Canon EOS 7D Master thread

Canon EOS 7D 400 mm f/5.6 1/2000 sec 640 ISO +1.5 EV

Edited on Oct 11, 2009 at 10:48 PM · View previous versions

Oct 11, 2009 at 10:16 PM

abqnmusa
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p.128 #18 · Canon EOS 7D Master thread

Canon EOS 7D 85 mm f/8.0 1/180 sec 100 ISO 0.0 EV

Oct 11, 2009 at 10:20 PM

abqnmusa
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p.128 #19 · Canon EOS 7D Master thread

Canon EOS 7D 17 mm f/4.0 1/20 sec 3200 ISO 0.0 EV

Edited on Oct 11, 2009 at 10:37 PM · View previous versions

Oct 11, 2009 at 10:28 PM

Yakim Peled
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p.128 #20 · Canon EOS 7D Master thread

I don't get it. You post actual pictures? But who cares? We want pixels, facts, graphs and math, not pictures. What's the point of using the camera this way?

Happy shooting,
Yakim.

Oct 11, 2009 at 10:32 PM

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