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Author Topic: Leaf's advertising - why the false claims?  (Read 18288 times)

Rob B.

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Re: Leaf's advertising - why the false claims?
« Reply #60 on: April 21, 2013, 05:42:24 PM »

Edmund,

Quote from: eronald
I think you genuinely believe this degree of DR is not of practical relevance; aside from the fact that one could do one-shot HDR, I am pointing out that it IS relevant because in fact pushed DR is what allows modern digital backs to simulate ISO higher than 100...

Relax. Your credentials are safe. I simply was not aware of this information. Thank you for helping me to understand.

Erik,

Quote from: ErikKaffehr
I have recently made a posting where I indicated that DR was overemphasised. I still think it is, but I found several images with DR in the 11-13 EV range. If you include setting sun, for instance and want decent foreground drawing you need all the DR you can get. The reason is that you need to underexpose intentionally to minimize clipping on the highlights. It is not underexposure, technically I would say it is correct ETTR.

Thank you for the link. I have previously read the thread. :)

Fred,

Quote from: FredBGG
There are endless exampekls in the real world where this is an enourmous advantage. If this were not the case Kodak would not have strived for years to increase dynamic range of negative film.

I do not doubt it. However, my original post did not refer to film, but to a state of the art digital sensor.

I appreciate that the dynamic range of some compositions will exceed the latitude of the sensor. What I queried was the practical usefulness of having such scope for adjustment in a sensor that natively has the ability to capture significant dynamic range. However...

Quote from: FredBGG
What is importasnt with the example I posted is that even in exteeme cases the results are still very good. This meands that in more commomn practial cases the quality will be even higher.

This makes sense. :) Thank you.
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ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #61 on: April 21, 2013, 05:45:05 PM »

However, no one I know deliberately shoots images grossly under-exposed and then pushes the file to the extent indicated in Fred's post. If doing so is useful for some then it is news to me, hence my question to Fred.

Deliberately grossly underexposing and pushing is more common than you think: it is the definition of high-ISO shooting with any camera with a flat readnoise-vs-ISO curve. That includes all MFD cameras, and nearly all recent Sony-sensored CMOS cameras, like the D800 itself.

So unless Nikon are screwing around with the RAW data (and they admittedly have poor form in that regard - messing up the stats by subtracting the bias, and median-filtering hot pixels in long exposures), then Fred's photo above - let's say it was at ISO 100 and 5 stops underexposed - would give virtually the exact same RAW file if it were a correctly exposed ISO 3200 shot.

A system with high DR will also have a good high ISO performance and it will be able to to do the FredBG trick.

That is true of most cameras one encounters these days, yet it is not really correct to make it a general rule.
High DR can result from either large full well capacity or low readout noise. In the latter case, the camera will also be particularly good for high ISO. But in the former case, it won't...the CCDs in MFD systems are good examples of this.

So it is better not to explicitly couple DR with high ISO ability: because there are high-DR cameras (like the Dalsa-sensored MFD ones at their native pixel sizes) that are disappointing when it comes to high ISO.

It is possible to achieve good ISO performance with little DR, if the sensor is clean but readout circuitry is weak using variable pre amplification, that is pretty much what Canon does.

Exactly. And that's another reason why it is better not to explicitly couple DR with high ISO ability: because there are high-ISO cameras that are disappointing when it comes to high DR.

The perfect sensor would have both large full well capacity and low readout noise. Sony and Fuji are getting close with their latest CMOS APS/FF sensors, although the smallish pixel sizes favoured these days limit how large the full well capacity can get.

Ray
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Rob B.

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Re: Leaf's advertising - why the false claims?
« Reply #62 on: April 21, 2013, 05:56:18 PM »

Ray,

Quote from: ondebanks
Deliberately grossly underexposing and pushing is more common than you think: it is the definition of high-ISO shooting with any camera with a flat readnoise-vs-ISO curve.

Yes, I can see now that I was ignorant of the way in which cameras return their high ISO performance. Thank you for clarifying. :)
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ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #63 on: April 21, 2013, 05:59:26 PM »

Ray,

Yes, I can see now that I was ignorant of the way in which cameras return their high ISO performance. Thank you for clarifying. :)

You're very welcome...glad that my explanation helped.

Ray
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ErikKaffehr

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Re: Leaf's advertising - why the false claims?
« Reply #64 on: April 21, 2013, 11:51:49 PM »

Ray,

You are of course right. I forgot that MFD-s tend to have low base ISO. My reasoning was that if we ETTR the dynamic range will be fully utilized. So if we have large dynamic range we can underexpose a number of steps. But if a sensor has low base ISO, like 50 and we push three stops we still just get 400 ISO with a three exposure push.

One of the great mysteries with MF in my view is the low base ISO, but I guess things add up. No microlenses, perhaps more othogonal CGAs? Pixel size should be ISO neutral, as FWC is proportional to pixel area, but so is the number of incident photons.

Learning in small bits...

Best regards
Erik


That is true of most cameras one encounters these days, yet it is not really correct to make it a general rule.
High DR can result from either large full well capacity or low readout noise. In the latter case, the camera will also be particularly good for high ISO. But in the former case, it won't...the CCDs in MFD systems are good examples of this.

ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #65 on: April 22, 2013, 06:02:05 AM »

One of the great mysteries with MF in my view is the low base ISO, but I guess things add up. No microlenses, perhaps more othogonal CGAs? Pixel size should be ISO neutral, as FWC is proportional to pixel area, but so is the number of incident photons.

"No microlenses, perhaps more othogonal CGAs" - together these add up to lower net quantum efficiency. Yes, that's a factor alright. One notices that the relatively few MFD cameras/backs with microlensed sensors have ~1 stop higher base ISO than their stablemates of the same pixel tech and size but without microlenses. P21+ vs P20+ and P25+; P30+ vs P45+; Hassy 31 vs 39 MP & 40 vs 50 MP...to take a few examples.

"Pixel size should be ISO neutral, as FWC is proportional to pixel area" - that's true in general, but don't forget the 3rd dimension - physical pixel junction depth into the wafer - and the "4th dimension" - the energy barrier set by the anode voltages, which control how densely one can pack the photo-electrons and still hold them in the "energy well". Like charges repel each other of course, so if you want to squeeze tens of thousands of negative electrons into a smaller volume, you need a stronger positive anode voltage centred on the pixel to overcome that repulsion.

So by exploiting at least one of these additional dimensions (I honestly have not checked which), Dalsa have often delivered greater FWCs for a given pixel area than Kodak. The other factor is that Kodak have pretty consistently had chips with higher spectral transmission efficiency than Dalsa. So the Kodaks have often had smaller pixel capacities AND they filled them at a faster rate: two things which raise the base ISO. This explains why hardly any Kodak-based MFD unit has had a base ISO of 25***, but several Dalsa ones have had...and when the Dalsa ones have started at ISO 50 or 80, the equivalent Kodak ones have started at ISO 100. 

Ray

***  AFAIK, only two Kodak-based MFD units have had a base ISO of 25: the Sinarbacks 44M and 54M. But I've never understood how, since all the other MFD manufacturers using these same two sensors have set their base ISO to 50 or even 100. Perhaps as tethered backs aimed at studio use, Sinar were setting them up for more extreme ETTR than would be safe under outdoor light conditions.
This highlights another factor which muddies the waters: manufacturers have some leeway to choose what they like for base ISO. Thus, to take a recent example, Phase One set the Dalsa 40MP sensor to ISO 50 in the P40+, while Leaf set it to ISO 80 in the Aptus-II 8. There can even be inconsistency for the same manufacturer: Leaf then went on to set the same sensor back to ISO 50 in the Credo 40. So perhaps one shouldn't read too much into the base ISO value, since deliberate variations of up to 1-stop for the same sensor are common.
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ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #66 on: April 22, 2013, 07:02:49 AM »

"Pixel size should be ISO neutral, as FWC is proportional to pixel area" - that's true in general, but don't forget the 3rd dimension - physical pixel junction depth into the wafer - and the "4th dimension" - the energy barrier set by the anode voltages, which control how densely one can pack the photo-electrons and still hold them in the "energy well".
....So by exploiting at least one of these additional dimensions (I honestly have not checked which), Dalsa have often delivered greater FWCs for a given pixel area than Kodak. 

And doh! - how could I have forgotten? - another likely reason for Kodak's smaller FWCs is that they (always?) have stronger anti-blooming than Dalsa, so they probably devote more pixel area to the overflow drain.

Ray
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Ben Rubinstein

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Re: Leaf's advertising - why the false claims?
« Reply #67 on: April 22, 2013, 10:47:04 AM »

I was looking at the sensor of my Aptus II-8 today, you can see the centre fold of the two joined sensors quite clearly. Serious question, why aren't they using a couple of D800 sensors joined together? The software can't be that hard if a small company like Leaf can do it (not knocking their achievement), it would give incredible image quality for significantly less cost would it not? Oh and allow stuff like real live view and incredible high iso. Please pardon me if the question is naive.

ced

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Re: Leaf's advertising - why the false claims?
« Reply #68 on: April 22, 2013, 11:36:58 AM »

And what shall they stick it together with superglue??
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Ben Rubinstein

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Re: Leaf's advertising - why the false claims?
« Reply #69 on: April 22, 2013, 11:44:39 AM »

Doug has informed me I was mistaken, the sensor in my back is not a dual co-joined sensor such as was in some backs, not sure what I'm seeing, there is a definite horizontal line running down the middle but apparently it's not a join. There were some backs using this method however were there not historians?
« Last Edit: April 22, 2013, 11:52:37 AM by Ben Rubinstein »
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ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #70 on: April 22, 2013, 12:15:36 PM »

Joining sensors would be wonderful in theory, but you would not be able to get active pixel butted right up against active pixel. There is always a perimeter of dummy and black reference pixels, and usually a lot of output pins...all these would get in the way, so every image would have a thick dark line down the middle. Research astronomers do put up with this in their mosaic-cams, but terrestrial photographers would not.

Ray
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ErikKaffehr

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Re: Leaf's advertising - why the false claims?
« Reply #71 on: April 22, 2013, 12:29:23 PM »

Hi,

I have considered the third dimension but noted that FWCs don't differ a lot between pixels of comparable sizes, so assumed that the third dimension is quite similar for all. My knowledge is not in microelectronics, just that I am interested.

It's nice to hear some good explanations from someone having insight. I learn a lot!

Best regards
Erik


"No microlenses, perhaps more othogonal CGAs" - together these add up to lower net quantum efficiency. Yes, that's a factor alright. One notices that the relatively few MFD cameras/backs with microlensed sensors have ~1 stop higher base ISO than their stablemates of the same pixel tech and size but without microlenses. P21+ vs P20+ and P25+; P30+ vs P45+; Hassy 31 vs 39 MP & 40 vs 50 MP...to take a few examples.

"Pixel size should be ISO neutral, as FWC is proportional to pixel area" - that's true in general, but don't forget the 3rd dimension - physical pixel junction depth into the wafer - and the "4th dimension" - the energy barrier set by the anode voltages, which control how densely one can pack the photo-electrons and still hold them in the "energy well". Like charges repel each other of course, so if you want to squeeze tens of thousands of negative electrons into a smaller volume, you need a stronger positive anode voltage centred on the pixel to overcome that repulsion.

So by exploiting at least one of these additional dimensions (I honestly have not checked which), Dalsa have often delivered greater FWCs for a given pixel area than Kodak. The other factor is that Kodak have pretty consistently had chips with higher spectral transmission efficiency than Dalsa. So the Kodaks have often had smaller pixel capacities AND they filled them at a faster rate: two things which raise the base ISO. This explains why hardly any Kodak-based MFD unit has had a base ISO of 25***, but several Dalsa ones have had...and when the Dalsa ones have started at ISO 50 or 80, the equivalent Kodak ones have started at ISO 100. 

Ray

***  AFAIK, only two Kodak-based MFD units have had a base ISO of 25: the Sinarbacks 44M and 54M. But I've never understood how, since all the other MFD manufacturers using these same two sensors have set their base ISO to 50 or even 100. Perhaps as tethered backs aimed at studio use, Sinar were setting them up for more extreme ETTR than would be safe under outdoor light conditions.
This highlights another factor which muddies the waters: manufacturers have some leeway to choose what they like for base ISO. Thus, to take a recent example, Phase One set the Dalsa 40MP sensor to ISO 50 in the P40+, while Leaf set it to ISO 80 in the Aptus-II 8. There can even be inconsistency for the same manufacturer: Leaf then went on to set the same sensor back to ISO 50 in the Credo 40. So perhaps one shouldn't read too much into the base ISO value, since deliberate variations of up to 1-stop for the same sensor are common.

ErikKaffehr

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Re: Leaf's advertising - why the false claims?
« Reply #72 on: April 22, 2013, 12:32:37 PM »

Hi,

Sensors can be stitched on wafer in manufacture, and indeed it is my understanding that full frame sensors use one dimentional stitching. An MF sensor woud require multidimensional stitching.

Best regards
Erik

Joining sensors would be wonderful in theory, but you would not be able to get active pixel butted right up against active pixel. There is always a perimeter of dummy and black reference pixels, and usually a lot of output pins...all these would get in the way, so every image would have a thick dark line down the middle. Research astronomers do put up with this in their mosaic-cams, but terrestrial photographers would not.

Ray

ErikKaffehr

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Hi,

We have many happy MF owners on this forums. Obviously MF sensors would probably have some advantages. I have not seen so many Apples to Apples comparisons between sensors of different size.

Personally, I think that we have some advantage in higher photon count at base ISO, thus having better shot noise. Also I can presume that CGA may be more optimized for color separation than for high ISO. That may give MF an advantage.

Regarding color, I would ask if there would be a major difference in color if we made a comparison with white balance set on a gray card and if we used color profiles genareted by the same software, like Xrite Color Checker Passport or Adobe DNG profile editor?

Best regards
Erik

Doug Peterson

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Re: Leaf's advertising - why the false claims?
« Reply #74 on: April 22, 2013, 12:46:23 PM »

Doug has informed me I was mistaken, the sensor in my back is not a dual co-joined sensor such as was in some backs, not sure what I'm seeing, there is a definite horizontal line running down the middle but apparently it's not a join. There were some backs using this method however were there not historians?

I guess it's a matter of semantics what you call it (e.g. "stitch" vs "etch" vs "segmented").

Most modern medium format CCDs have more than one read out area, which requires a read-out channel transit the sensor, which creates a visual line when you hold the sensor at an angle to direct light. They are exposed on a single piece of silicon however, and are not "joined" in the sense that they do not create sensors and then glue them together. Such an approach would be extremely hard to use in made-for-standard-photographic-applications camera since, as pointed out above you'd have to have butt them together within one pixel (e.g. 6 microns) apart and then calibrate them to produce nearly identical read-outs across a huge spectrum of possible exposures.

FredBGG

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Re: Leaf's advertising - why the false claims?
« Reply #75 on: April 22, 2013, 12:53:04 PM »

Doug has informed me I was mistaken, the sensor in my back is not a dual co-joined sensor such as was in some backs, not sure what I'm seeing, there is a definite horizontal line running down the middle but apparently it's not a join. There were some backs using this method however were there not historians?

The sensor is not made out of two chips physically joined together, however the chip is manufactured one area at a time due to the maximum size
that can be made at on time by the stepper.The chip is moved between tiles. This is why they are visable to the naked eye when looking at the sensor.
Calibration has to be performed to not make the bounderies visable in final images. Not all copies of sensors will have the same precision. It is very complicated to reposition the chip between tiles when tollerences are so infinately small.



many people have had issues with these bouderies showing up. Both calibration and software tricks help resolve the issue.
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FredBGG

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Re: Leaf's advertising - why the false claims?
« Reply #76 on: April 22, 2013, 01:06:33 PM »

I guess it's a matter of semantics what you call it (e.g. "stitch" vs "etch" vs "segmented").

Most modern medium format CCDs have more than one read out area, which requires a read-out channel transit the sensor, which creates a visual line when you hold the sensor at an angle to direct light. They are laser etched out of a single piece of silicon however, and are not "joined" in the sense that they do not create sensors and then glue them together. Such an approach would be extremely hard to use in made-for-standard-photographic-applications camera since, as pointed out above you'd have to have butt them together within one pixel (e.g. 6 microns) apart and then calibrate them to produce nearly identical read-outs across a huge spectrum of possible exposures.

Are CCDs made by etching with a laser?
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ErikKaffehr

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Re: Leaf's advertising - why the false claims?
« Reply #77 on: April 22, 2013, 03:38:27 PM »

Not as far as I know. Chips are normally made in a photolitographic processs.

Best regards
Erik

Are CCDs made by etching with a laser?

ondebanks

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Re: Leaf's advertising - why the false claims?
« Reply #78 on: April 22, 2013, 08:11:38 PM »




What back is that, Fred? Looks like a 60 or 80 MP full 645 frame?

With this discussion of multiple stepper blocks laid down on a single MFD chip, I think we strayed away from Ben's question, which was about "using a couple of D800 sensors joined together". A system which integrates multiple self-contained sensors could be done, but not gaplessly, for the reason I gave above.

However, such an array of sensors might be good for stitching panos in a very short time, or simulating much larger formats - two slightly displaced shots would be all you need to fill in the gaps. Think of Fotodiox's RhinoCam concept, with not one NEX camera, but several NEX sensors (or D800 sensors) side by side.

Ray
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FredBGG

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Re: Leaf's advertising - why the false claims?
« Reply #79 on: April 23, 2013, 03:15:57 AM »

Not as far as I know. Chips are normally made in a photolitographic processs.

Best regards
Erik


Like this:

http://youtu.be/bqJksXwrx7U

maybe lasers are used to etch new sensors, but it's the first time i've heard of it.
Maybe Doug could explain it in more detail.
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