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Author Topic: Another Stupid Camera Test: IQ 260 / A7r / 5d2 / Epic  (Read 20482 times)
Chris Livsey
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« Reply #140 on: January 05, 2014, 11:42:31 AM »
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I am in favour of reducing pixel size within reasonable bounds. It may be diminishing returns, but I am pretty sure that smaller pixels will sharpen better, interpolate better and have less aliasing.

Best regards
Erik


Erik, I'm getting confused now  Roll Eyes

I read a lot recently and not only on this forum about how good the "old" backs were, no, still are, with their "fat pixels".
Do we want/need/prefer smaller pixels or larger pixels, or are the trade offs such that perfection in either camp means we accept the compromises of each approach?

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Chris Livsey
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torger
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« Reply #141 on: January 06, 2014, 11:31:58 AM »
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I think the appreciation of the "fat pixel" backs comes from several things.

Most (not all) of the fat pixel backs have kodak sensors which had a special saturated look, a bit like color reversal film, a look which many fall in love with. This look could be recreated with smaller pixels too, but later chips (dalsa) has chosen another more neautral approach to color which many prefer too.

I think there's also a bit of disappointment from users that most improvements has been in increased resolution, while many actually would like to see something like a 40 megapixel 6x6 sensor rather than a 80 megapixel 645 which we now have. The increased resolution has put higher requirements and cost on optics to resolve that (and feed the sensor with close-to-perpedicular light), and many would prefer optics that concentrate more on look and less on resolving power.

Life was easier in the fat pixel days, almost any lens worked well and delivered razor-sharp images in pixel peeping which is a special kind of satisfaction :-)

Concerning noise and full-well capacity etc I don't think those older fat pixel where any better in any pratical way, a modern small pixel is better at delivering a clean signal than an old fat pixel.

I read a lot recently and not only on this forum about how good the "old" backs were, no, still are, with their "fat pixels".
Do we want/need/prefer smaller pixels or larger pixels, or are the trade offs such that perfection in either camp means we accept the compromises of each approach?
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ErikKaffehr
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« Reply #142 on: January 07, 2014, 01:04:25 PM »
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Hi,

Sorry for not responding, I had problem with my internet connection.

One of the problems with fat pixels is that lens resolves more information than the sensor. This will lead to sensor generating spurious resolution or as I would call it "fake detail". The most well know is color moiré, but there is also monochrome moiré, color aliasing and jaggies.

I recently shot an aperture series with my P45+ and a Planar 80/2.8 lens at apertures at f/5.6 to f/22. All images up to f/11 showed a lot of artefacts, which suddenly went away at f/16. See enclosed pictures. The P45 has 6.8 my pixels.

I also the same subject with a 16-80/3.5-4.5 zoom lens on my Sony Alpha 77 at 80 mm and same distance, using f/8. The Sony Alpha 77 has 24 MP at 3.9 my, and with a full frame 645 back that would correspond to 143 MP. The Alpha 77 may be OLP filtered or not, I don't actually know.

Reducing pixel size reduces DR. Halving the pixel diameter would reduce DR by one EV, if all other factors were constant. Midtone and highlight noise level would be very little affected as it is mostly dependent on the number of incident photons captured and that is mostly a function of the sensor area.

Halving pixel size would not quadruple the information content, however, as MTF would be reduced at smaller pixel sizes.

The third enclosed image shows that a 3.9 my sensor would get much better detail.

Best regards
Erik

Erik, I'm getting confused now  Roll Eyes

I read a lot recently and not only on this forum about how good the "old" backs were, no, still are, with their "fat pixels".
Do we want/need/prefer smaller pixels or larger pixels, or are the trade offs such that perfection in either camp means we accept the compromises of each approach?


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Chris Livsey
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« Reply #143 on: January 07, 2014, 02:06:49 PM »
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Thank you both.

Torger, was/is the colour look a result of the filtration used? Surely only from the "profile" used to de mosaic the data? If so the same "look" could come from the Dalsa series?
The question is was that "look" which is attributed to the fat pixels not a result of pixel size but of the software?

Erik,
Indeed the detail "captured" will improve as the pixel size decreases, but has the dynamic range not been maintained or indeed improved from the fat pixel backs as the "read" technology and associated sensitivity and amplification have improved over time?

Sorry if this has strayed from the thread title but as a fat pixel owner, venerable P20, I always find the latest backs/cameras interesting to see if the "improvements" are real at the sizes I use as an amateur. Your patience is appreciated.


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Chris Livsey
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ErikKaffehr
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« Reply #144 on: January 07, 2014, 02:57:55 PM »
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Hi,

The short version:

Sensors have gotten better. Making pixels smaller reduces the DR per pixel but the increased number of pixels helps a lot.

The long version, see below:

DR is a bit tricky. The technical definition is FWC/readout noise, with WFC is being Full Well Capacity, the number of electrons a pixel can hold. Readout noise is the noise in reading out the electrons.

For medium size pixels like (6 my) the FWC may be around 60000 electrons FWC is by and large proportional to pixel surface, even if I think some progress have been made. The major factor in DR has probably been the reduction in readout noise. Modern CMOS may have say 3 electron charges in readout noise while CCD is more like 12-15 electron charges.

Let's assume we have a P45+ with 6.8my pixels, and let it compare to a 3.4 my pixel sensor using modern CMOS-technology. Let's assume 65000 electron charges (EC) per pixel for the P45+ and 16 EC in readout noise. So we have 65000/16=4062, converting to EV we get 11.99 EV. DxO-Mark measures 11.75 EV at 50 ISO (in 'screen, mode).

Now, let's take a CMOS sensor with half of that diameter, and assume FWC  65000/4 = 16250, if we assume 4EC in readout noise we would get a DR of 4062 that is 11.98, nearly the same as the "fat pixel CCD".

Now the small pixel CMOS has four pixels instead of one. Would be print both at the same size and assuming a sensor of the same size, the combined FWC would be 65000, read noise adds in quadrature, so we would have sqrt (4 * 4 * 4) = 8

So DR would be 12.98 EV, the smaller CMOS pixels would have a 1 EV advantage over the large pixel CCD. Would we do the same math with a CCD instead, FWC would still be at 65000 but readout noise would be 32. So DR would reduce to 10.98 EV.

Newer generations of CCD sensors have less readout noise than the older ones, but they are still in the low tens. Regarding CMOS, some sensors have external analog-digital converters (ADC), the off chip ADCs tend to be noisy, so these cameras have CCD like readout noise. Many modern CMOS sensors have thousands of on chip converters that work in parallell, these are much less noisy.

What complicates the issues is that DR I describe is a technical definition, and represents a level of noise where the signal is barely perceptible. In photographs we want a better Signal Noise ratio (SNR), on the other hand lower end of the DR scale is normally what I would call deep shadows where we would have little detail anyway.

Midtones and highlights are more affected by "shot noise", the natural variation of incident photons, which is independent of the sensor technology and depends only on exposure, sensor surface and quantum efficiency QE). QE is the percentage of the incoming photons that are detected.

Hope this helps! Here is a recommended paper, describing it more deeply: http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/index.html

Best regards
Erik




Thank you both.

Torger, was/is the colour look a result of the filtration used? Surely only from the "profile" used to de mosaic the data? If so the same "look" could come from the Dalsa series?
The question is was that "look" which is attributed to the fat pixels not a result of pixel size but of the software?

Erik,
Indeed the detail "captured" will improve as the pixel size decreases, but has the dynamic range not been maintained or indeed improved from the fat pixel backs as the "read" technology and associated sensitivity and amplification have improved over time?

Sorry if this has strayed from the thread title but as a fat pixel owner, venerable P20, I always find the latest backs/cameras interesting to see if the "improvements" are real at the sizes I use as an amateur. Your patience is appreciated.



« Last Edit: January 07, 2014, 03:01:21 PM by ErikKaffehr » Logged

Chris Livsey
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« Reply #145 on: January 08, 2014, 04:23:38 PM »
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Erik, I like the long version. Grin
Large v small pixels is a simplification, well explained. It was, when laid out like this, amazing they did so well with CCD, but the advances in chip design and production have enabled so much more "efficiency" in signal handling. The other problem, dragging this back OT, in comparisons is the "processing" done before the RAW. This Sony in particular uses a number of "tricks" on the output as our erudite analysers have shown but it is a game changer, more than the D3 then D800 were, they were landmarks perhaps to stretch analogies.
Not mentioned because, although I know we have a number of video/mixed media users, we tend to discuss the still potential is the video which I see, from Philip Bloom, could, with a bit of tweaking from Sony be outstanding rather than pretty good.

 Thanks for the link, i have seen it before. I start really well then it sort of slides away from me for a while then suddenly I'm back with some understanding. I visited the Ilford factory in the UK earlier this year and that was so many worlds away, a different planet.
« Last Edit: January 08, 2014, 04:26:12 PM by Chris Livsey » Logged

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Chris Livsey
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eronald
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« Reply #146 on: January 08, 2014, 08:58:31 PM »
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So much tweaking, so little ground truth ...

Edmund

Erik, I like the long version. Grin
Large v small pixels is a simplification, well explained. It was, when laid out like this, amazing they did so well with CCD, but the advances in chip design and production have enabled so much more "efficiency" in signal handling. The other problem, dragging this back OT, in comparisons is the "processing" done before the RAW. This Sony in particular uses a number of "tricks" on the output as our erudite analysers have shown but it is a game changer, more than the D3 then D800 were, they were landmarks perhaps to stretch analogies.
Not mentioned because, although I know we have a number of video/mixed media users, we tend to discuss the still potential is the video which I see, from Philip Bloom, could, with a bit of tweaking from Sony be outstanding rather than pretty good.

 Thanks for the link, i have seen it before. I start really well then it sort of slides away from me for a while then suddenly I'm back with some understanding. I visited the Ilford factory in the UK earlier this year and that was so many worlds away, a different planet.
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Chris Livsey
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« Reply #147 on: January 09, 2014, 01:33:15 AM »
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So much tweaking, so little ground truth ...

Edmund


I suppose if Sony made a full, frank and open disclosure all the reverse engineering Depts. in Nikon, Panasonic, Canon etc etc would be redundant, we don't want that do we?
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Chris Livsey
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torger
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« Reply #148 on: January 09, 2014, 02:42:25 AM »
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Torger, was/is the colour look a result of the filtration used? Surely only from the "profile" used to de mosaic the data? If so the same "look" could come from the Dalsa series?
The question is was that "look" which is attributed to the fat pixels not a result of pixel size but of the software?

I need to speculate a bit, because I don't know for sure. But it seems likely that it is a combination of the design of color filters on the sensor itself and the profiles used for the cameras in the raw converter.

The Dalsa series don't have the same color filters on the sensor so the exact same look cannot be reproduced, but you can probably come quite close.

I'm almost 100% sure that the look has nothing to do with the pixel size though, ie you could design a new sensor with smaller pixel size but with the same color filters and profile in the software and get the same look. New sensors just don't use the same color filters as they did back then.

One theory often mentioned is that the fat pixel has larger full well capacity and thus captures more photons which would somehow affect the look in a positive way. However one need to look at the total amount of captured photons and also read noise, and then modern sensors are substantially better, so I don't think that theory holds up.
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eronald
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« Reply #149 on: January 09, 2014, 05:38:27 AM »
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More orthogonal filters, sensor considerably outresolved by the lens,  - you can see how well these systems perform by the incessant complaints about Moiré Smiley

Edmund

I need to speculate a bit, because I don't know for sure. But it seems likely that it is a combination of the design of color filters on the sensor itself and the profiles used for the cameras in the raw converter.

The Dalsa series don't have the same color filters on the sensor so the exact same look cannot be reproduced, but you can probably come quite close.

I'm almost 100% sure that the look has nothing to do with the pixel size though, ie you could design a new sensor with smaller pixel size but with the same color filters and profile in the software and get the same look. New sensors just don't use the same color filters as they did back then.

One theory often mentioned is that the fat pixel has larger full well capacity and thus captures more photons which would somehow affect the look in a positive way. However one need to look at the total amount of captured photons and also read noise, and then modern sensors are substantially better, so I don't think that theory holds up.
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ErikKaffehr
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« Reply #150 on: January 09, 2014, 11:51:42 PM »
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Hi,

Perception may play a role. Also when looking at an image at actual pixels, the larger pixels will mostly have an advantage. But quantity has a quality of it's own.

Best regards
Erik

More orthogonal filters, sensor considerably outresolved by the lens,  - you can see how well these systems perform by the incessant complaints about Moiré Smiley

Edmund

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« Reply #151 on: January 10, 2014, 12:47:00 PM »
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was a bit miffed with the raws Chris so kindly posted up as there were areas of colour that didn't look right to me especially the yellow by the fireplace where mixed lighting hasn't helped the smooth tones but they looked very posterised and gritty in adobe raw. tried the new capture one and i'm now interested in this camera again.
not a scientific test but i gave the shadows a boost and roughly tried to match them by adding some saturation in AR. C1 has done a much better job of handling this area.

« Last Edit: January 10, 2014, 02:36:08 PM by MrSmith » Logged
ErikKaffehr
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« Reply #152 on: January 11, 2014, 03:29:01 AM »
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Hi,

I took a good look at that are in both LR 5.3 and Capture 1. Regarding the LR 5.3 image I have seen a similar effect and in my case it came from masking feature in the sharpening group of keys. Increasing masking will reduce/eliminate the artefacts.

Explanation: masking essentially hides sharpening in low contrast areas. So what you probably see is the bounds of masked and unmasked areas.

Best regards
Erik

was a bit miffed with the raws Chris so kindly posted up as there were areas of colour that didn't look right to me especially the yellow by the fireplace where mixed lighting hasn't helped the smooth tones but they looked very posterised and gritty in adobe raw. tried the new capture one and i'm now interested in this camera again.
not a scientific test but i gave the shadows a boost and roughly tried to match them by adding some saturation in AR. C1 has done a much better job of handling this area.


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MrSmith
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« Reply #153 on: January 11, 2014, 04:22:50 AM »
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I thought it was something to do with the compressed raw not the adobe defaults that encourage posterisation and gritty shadows. Huh 
I didn't use Lightroom but adobe raw (I presume the processing is the same though) and just used the defaults apart from a bit of saturation in AR and a hefty lift of the shadows in both to help bring out any noise.
Sharpening was at default on AR with standard look on C1

The C1 tiffs were much better looking than the adobe IMHO.
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ErikKaffehr
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« Reply #154 on: January 12, 2014, 02:25:59 AM »
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Hi,

I don't own the A7r and it is not on my shopping list, so I have now experience with it on my own. I have looked at the Sony data compression and I would say there is nothing that would cause artefacts.

I processed the images in both Capture 1 and Lightroom 5.3, I have much more experience with LR. Screen dumps of the results are enclosed.

Best regards
Erik




I thought it was something to do with the compressed raw not the adobe defaults that encourage posterisation and gritty shadows. Huh 
I didn't use Lightroom but adobe raw (I presume the processing is the same though) and just used the defaults apart from a bit of saturation in AR and a hefty lift of the shadows in both to help bring out any noise.
Sharpening was at default on AR with standard look on C1

The C1 tiffs were much better looking than the adobe IMHO.
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« Reply #155 on: January 12, 2014, 04:16:04 AM »
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with your processing they are very close (LR has more sharpening) i guess your familiarity with LR got the best out of the file.
i dont use LR or AR only C1. they were both at default except for a shadow lift to bring out any noise and a small increase in saturation for AR to match to C1. i guess the A7r profile in C1 gets you most of the way there but adobe needs tweaking to remove the posterisation/artefacts.

good to see raw compression has not adversely affected the images though.
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ErikKaffehr
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« Reply #156 on: January 12, 2014, 04:27:24 AM »
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Hi,

It is also the other way around, my lack of skill with C1 matters a lot.

Best regards
Erik



with your processing they are very close (LR has more sharpening) i guess your familiarity with LR got the best out of the file.
i dont use LR or AR only C1. they were both at default except for a shadow lift to bring out any noise and a small increase in saturation for AR to match to C1. i guess the A7r profile in C1 gets you most of the way there but adobe needs tweaking to remove the posterisation/artefacts.

good to see raw compression has not adversely affected the images though.
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Theodoros
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« Reply #157 on: January 12, 2014, 05:05:51 AM »
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Hi,

It is also the other way around, my lack of skill with C1 matters a lot.

Best regards
Erik



Erik, it's a surprise to me that you don't use C1P1at least with your P45+… You should really give it another go… it makes (especially with your back) a lot of difference, MO is that this way you compare a "crippled" back which makes it very unfair for it.
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ErikKaffehr
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« Reply #158 on: January 12, 2014, 05:25:52 AM »
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Hi,

I had used it for nine months and I decided that LR 5 works better with me. Capture One is history for me!

I had rechecked C1 vs LR5 on some recent images and I still don't feel C1 is better. May be LR5 takes a bit more work, but I find it works better for me.

Best regards
Erik


Erik, it's a surprise to me that you don't use C1P1at least with your P45+… You should really give it another go… it makes (especially with your back) a lot of difference, MO is that this way you compare a "crippled" back which makes it very unfair for it.
« Last Edit: January 12, 2014, 04:22:55 PM by ErikKaffehr » Logged

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« Reply #159 on: January 13, 2014, 01:07:25 AM »
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I had rechecked C1 vs LR5 on some recent images and I still don't feel C1 is better. May be LR5 takes a bit more work, but I find it works better for me.

If you had just written that you preferred LR5, that'd be like okay makes sense, everyone is different.   But if you write you think LR5 is better than C1 and you have a phase back, I really am surprised as I have posted to the other thread.  There are some things LR does well, some very well, but its not the equal when all is considered.  I still use LR and sometimes I'll render a RAW in C1 and then continue working in LR or Photoshop.
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