Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: lance_schad on November 07, 2011, 04:43:34 pm
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Just read that Kodak sold its Image Sensor Business to Platinum Equity. I am sure more details will surface, but here is the link (http://www.rttnews.com/Content/QuickFacts.aspx?Id=1754251&SM=1) to an article which has some information .
Two big players in MFD still rely heavily on Kodak, Hasselblad and Lecia.
Phase One has two models that still use the Kodak sensors, the P30+ and P45+, but all their newer systems are based around a co-developed Dalsa sensor.
Lance
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Two big players in MFD still rely heavily on Kodak, Hasselblad and Lecia.
and Pentax 645D
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Two big players in MFD still rely heavily on Kodak, Hasselblad and Lecia.
And Pentax right, probably the largest of all in terms of sensors order volume.
Cheers,
Bernard
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That is very sad for the industry.
I feel we are loosing all the player in the photography business one by one.
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selling it to an equity company may not actually change much ...
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selling it to an equity company may not actually change much ...
It is unfortunately always the risk that the company changes its strategy. MFDB market may prove unattractive to new owners. It is always better to sell for the defense industry ... There turn billions, not millions.
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It is unfortunately always the risk that the company changes its strategy. MFDB market may prove unattractive to new owners. It is always better to sell for the defense industry ... There turn billions, not millions.
Empty speculation. It is a "risk" always that a company changes its strategy, whether it's a private equity firm or Kodak itself. Besides, Kodak is in huge financial trouble, so the future of the sensor business would have been far from certain there.
And although I don't know, I'm 100% sure Kodak already sells sensors to the defense industry.
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Empty speculation. It is a "risk" always that a company changes its strategy, whether it's a private equity firm or Kodak itself. Besides, Kodak is in huge financial trouble, so the future of the sensor business would have been far from certain there.
And although I don't know, I'm 100% sure Kodak already sells sensors to the defense industry.
Sure, but this risk is higher when company change owner. 2000 matrix PA for MFDB it is not a lot.
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Kodak is dead, the body just hasn't been pronounced.
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Sure, but this risk is higher when company change owner. 2000 matrix PA for MFDB it is not a lot.
Pentax 645D: at least 6000 units per year: http://www.pentax.jp/japan/news/2010/201008.html later rumors and serial numbers suggest that Pentax increased production to 700 units per month so maybe closer to 8400 per year
Leica S2: 1000 units per year if I recall correctly Mr. Farkas' estimation
Hasselblad: ???
Total: very conservative 8-9k sensors or IMO a more realistic estimation well over 10K MF sensors made by Kodak in one year.
Radu
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Pentax 645D: at least 6000 units per year: http://www.pentax.jp/japan/news/2010/201008.html later rumors and serial numbers suggest that Pentax increased production to 700 units per month so maybe closer to 8400 per year
Leica S2: 1000 units per year if I recall correctly Mr. Farkas' estimation
Hasselblad: ???
Total: very conservative 8-9k sensors or IMO a more realistic estimation well over 10K MF sensors made by Kodak in one year.
Radu
Sorry but I don't think about Leica S2 as a MFDB. I know that pentax sell a lot, but this matrix is made only for them.
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Sorry but I don't think about Leica S2 as a MFDB.
Your opinion isn't universal:
http://forum.getdpi.com/forum/showthread.php?t=31316
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Sorry but I don't think about Leica S2 as a MFDB. I know that pentax sell a lot, but this matrix is made only for them.
I think that the sensor in the 645D is the very same in the H4D 40 (KAF40000) of the shelf and not custom made (probably Pentax gets is much lower in price due to very large order comparative) and the sensor in S2 (KAF37500) is based on the same cells but with another form factor.
Radu
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Hi,
It is a MF DSLR, not an MF Digital Back. Regarding MF, I presume it simply means larger than 135 full frame.
Best regards
Erik
Your opinion isn't universal:
http://forum.getdpi.com/forum/showthread.php?t=31316
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Sorry but I don't think about Leica S2 as a MFDB. I know that pentax sell a lot, but this matrix is made only for them.
If you don't think the S2 is MF, you haven't shot one. The pentax chip is essentially identical to the H4-40, afaik. But the whole idea of selling it is that it's a viable business. That hardly suggests an intention to shut it down. The question is leadership and direction and, more to the point, whether anyone will be interested in CCD sensors next year.
- N.
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If you don't think the S2 is MF, you haven't shot one. The pentax chip is essentially identical to the H4-40, afaik. But the whole idea of selling it is that it's a viable business. That hardly suggests an intention to shut it down. The question is leadership and direction and, more to the point, whether anyone will be interested in CCD sensors next year.
- N.
1) I shot with S2, and I don;t change my mind
2) No it;s not the same chip
3) Not in all cases, sometimes PE companies buy Trademark. Sometimes only improve company and sell it
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Hi,
With CCD-sensors it's not all about the sensor, there are of chip ADCs and also pre amplifiers. I got the impression that Pentax is very good on analogue electronics side. With modern CMOS it seems that Sony has integrated ADCs on chip, in a way that massively benefits read noise.
I got the impression that Pentax 645D is really good at keeping read noise down on the 645D. They may be champ on DR regarding low end MF. Leica may be champ on lenses. On the other hand it seems that Mamiya knows how to build good lenses and so does Schneider.
Best regards
Erik
1) I shot with S2, and I don;t change my mind
2) No it;s not the same chip
3) Not in all cases, sometimes PE companies buy Trademark. Sometimes only improve company and sell it
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I got the impression that Pentax 645D is really good at keeping read noise down on the 645D.
Hi Eric,
Have you seen any measurements? I'd like to compare its actual readnoise to the Kodak spec.
Anyone here got a 645D? Yes, I know several of you do. Could one of you lucky 645D-ers please give 10 minutes of your time to
- take two frames at each ISO setting, with the lenscap ON, at the shortest shutter speed (1/4000 sec if I'm not mistaken)
- put the RAW files on somewhere like Dropbox, where I can download them.
I'll convert them to FITS format and do the usual calcs in IRAF; and then we'll know.
BTW: Leica, Hasselblad, Leaf, Sinar, PhaseOne and Mamiya users - I'd be delighted if any of you could volunteer to do the same. For some time I've been thinking of compiling a database, a public resource, of MFD sensor characterisations; getting at the important stuff that DxOmark doesn't cover, and all the MFD models that they've simply never tested.
Cheers,
Ray
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1) I shot with S2, and I don;t change my mind
2) No it;s not the same chip
3) Not in all cases, sometimes PE companies buy Trademark. Sometimes only improve company and sell it
Come to think of it, you're right. The S2 focuses, has good battery life and is ruggedly weather sealed. Clearly not MF ;) ;D
What will be interesting to see is the management team the buyers put in place. That will give us a good sense of where they're taking it. Not a play I'd want any part of, but may the force be with them. Contrary to what their name might suggest, Platinum Equity appears to be a bona fide outfit, and not some sort of massage parlour conglomerate. Curious to see what they will do with this acquisition.
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Pretty diverse portfolio Platinum Equity has. There are few that are familiar to me including Quark & USRobotics.
3B The Fibreglass Company
Active Aero Group
Acument Global Technologies
Alliance Entertainment
American Commercial Lines
Americatel
Canvas Systems
Contego Packaging Group
Data2Logistics
DCA Services
ECKA Granules
Geesink Norba Group
International Offshore Services
KEMET Corporation
Keystone Automotive Operations
Matrix Business Technologies
Maxim Crane Works
MegaPath
NESCO
Palace Sports & Entertainment
PBH Marine Group
PEAK Technologies
Pomeroy
Quark
Ryerson
Schutt Sports
SCM Metal Products
The San Diego Union-Tribune
Turf Care Supply Corp
Ulticom
US Robotics
Vanguard Networks
Wheel Pros
Lance
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Hi Ray,
The only measurements I have seen were on DxO-mark. When the 645D arrived I got the impression that it handled read noise really well. My understanding is that DR that DxO-mark measures is dominated by read noise. It is also my understanding that with CCDs analog readout is not integrated on the chip but is on a separate PCB and I got the impression that the Pentax solution is really good. Since than DxO mark republished data on the P40+ and it seems be even better than the Pentax 645D.
I have played around with raw files from Pentax 645D (from Imaging Resource and Miles Hecker) and Leica S2 (with kind permission of Lloyd Chambers) I was not impressed by shadow noise on the S2.
The Leica S2 stuff is here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/38-observations-on-leica-s2-raw-images
The Pentax article is not about DR, but it's here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/51-a-closer-look-at-pentax-645d-image-quality
Your idea on MFD read out noise data base is very interesting. My impression is that MFDBs are surrounded with a lot of mythos, but I guess that only benefit of MFDBs over DSLR sensors is larger size. A larger sensor collects more photons, holds more electron charges and so on. A larger sensor may also have advantage in resolution and allow higher MTF on a given structure size. So no doubt that there are many benefits to MF digital.
Do you have any ideas about sample variation?
Best regards
Erik
Hi Eric,
Have you seen any measurements? I'd like to compare its actual readnoise to the Kodak spec.
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I don't wish any company or person bad, but I'm glad the sensor business is gone from Kodak.
I mean Kodak's business decisions in the last decade and a half have been awful, so if larger Kodak sensors are to be sparred it's probably best they went to a company that will actively pursue a profit and hopefully more innovation.
IMO
BC
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Come to think of it, you're right. The S2 focuses, has good battery life and is ruggedly weather sealed. Clearly not MF ;) ;D
What will be interesting to see is the management team the buyers put in place. That will give us a good sense of where they're taking it. Not a play I'd want any part of, but may the force be with them. Contrary to what their name might suggest, Platinum Equity appears to be a bona fide outfit, and not some sort of massage parlour conglomerate. Curious to see what they will do with this acquisition.
Nick,
At this point Leica and a massage parlour seem to have in common that customers keep coming back because they enjoy the experience. ;D
Edmund
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Betterlight and Creo both use Kodaks sensors.
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Both HP and Kodak seem to be learning their moves from the same play book. What a shame because both companies had some real excellent products that they've let go of or killed off. In this case I hope the
acquiring company extends the sensor line and technology. Even though I use a dalsa chipped back now, the kodak chipped backs have been my favorites.
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Perhaps a quote from Buddhism is relevant here. There is no permanence in anything. Everything is subject to change. It's a reality of existence.
We may cling on to things, ideas and persons in an emotional fashion, and decry their passing. But such passing is always inevitable, eventually, and should be accepted as the natural process it is.
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The S2 focuses
Not wishing to hijack the thread; but...S2 Focusing Fact and Fiction (http://diglloyd.com/blog/2010/20101221_2-LeicaS2Focusing.html)
If you are a subscriber you can read all the minutia - if not the executive summary linked too pretty much says it how it is.
Perhaps the Leica qualifies as MF after all ;D
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Creo's Leaf backs always used Phillips/Dalsa sensors, even during the time that Kodak owned that business before on-selling to Phase One. Kodak bought Creo for assets other than the Leaf MF part.
And while people are worrying about new ownership emphasizing markets like military rather than MF:
- Dalsa was acquired by Teledyne a while ago
- scientific, industrial, medical and military usage have long been the dominant market for large CCD sensors from both Kodak and Dalsa. To get an idea of product emphasis, just see what the companies say:
http://www.kodak.com/ek/US/en/Image_Sensor_Solutions/Applications.htm
http://www.teledynedalsa.com/corp/markets/products.aspx
http://www.teledyne.com/
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Hi,
I don't know...
Nick Devlin and Mark Dubovoy don't have a similar experience. I have great respect for Lloyd's testing, and he has images to show. On the other hand I also have great respect for Nick's and Mark's testing.
Best regards
Erik
Not wishing to hijack the thread; but...S2 Focusing Fact and Fiction (http://diglloyd.com/blog/2010/20101221_2-LeicaS2Focusing.html)
If you are a subscriber you can read all the minutia - if not the executive summary linked too pretty much says it how it is.
Perhaps the Leica qualifies as MF after all ;D
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Hi,
I don't know...
Nick Devlin and Mark Dubovoy don't have a similar experience. I have great respect for Lloyd's testing, and he has images to show. On the other hand I also have great respect for Nick's and Mark's testing.
Best regards
Erik
Erik, I can't say I have first hand experience with the S2 (other than fondling one lovingly in the camera store) on a shoot; so I am certainly not qualified to make a judgement on the S2 focusing. I have to take the word of Nick, Mark and Lloyd in relation to the S2.
What I would say is that Lloyd is the only one of the bunch to actually have made public an extensive test on the S2 in relation to focusing. And that carries more weight for me than flowery statements like 'deadly accurate'.
I suspect (and only suspect) that perhaps Mark finds the S2 'deadly accurate' because he doesn't shoot with high end DSLR's - which really are without question at the top of the 'deadly accurate' focus heap. Mark's dslr equivalent is a micro Panasonic isn't it? (I think thats what he took to Africa when he wrote up his return editorial - I would have to go back to be 100% certain) Not exactly top end auto focus compared to a 1D MKIV or Nikon D3S. I wonder if his 'deadly accurate' statement is more born out what he is used to shooting, rather than what really rules the roost in terms of auto focus.
I would really like to see some more s2 focus testing - its still very high on my list for purchase consideration. Really, I should just go borrow one and shoot over a weekend with it. Perhaps when more lenses become available ;D
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Hi,
On the other hand Mark has shimmed his Alpa back within 10 microns, has a special focusing ring that takes three turns to cover the focusing range and uses a laser rangefinder from Leica, AFAIK, so he knows a few things about focusing.
My own view? In my view live view is optimum.
Best regards
Erik
Erik, I can't say I have first hand experience with the S2 (other than fondling one lovingly in the camera store) on a shoot; so I am certainly not qualified to make a judgement on the S2 focusing. I have to take the word of Nick, Mark and Lloyd in relation to the S2.
What I would say is that Lloyd is the only one of the bunch to actually have made public an extensive test on the S2 in relation to focusing. And that carries more weight for me than flowery statements like 'deadly accurate'.
I suspect (and only suspect) that perhaps Mark finds the S2 'deadly accurate' because he doesn't shoot with high end DSLR's - which really are without question at the top of the 'deadly accurate' focus heap. Mark's dslr equivalent is a micro Panasonic isn't it? (I think thats what he took to Africa when he wrote up his return editorial - I would have to go back to be 100% certain) Not exactly top end auto focus compared to a 1D MKIV or Nikon D3S. I wonder if his 'deadly accurate' statement is more born out what he is used to shooting, rather than what really rules the roost in terms of auto focus.
I would really like to see some more s2 focus testing - its still very high on my list for purchase consideration. Really, I should just go borrow one and shoot over a weekend with it. Perhaps when more lenses become available ;D
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On the other hand Mark has shimmed his Alpa back within 10 microns, has a special focusing ring that takes three turns to cover the focusing range and uses a laser rangefinder from Leica, AFAIK, so he knows a few things about focusing.
Insert the word 'manual' before focusing and I would agree with you. ;D
BTW: I agree with you. In my own experience, Live View is optimum
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In my experience close AF and long distance AF quality have no relation on an SLR. My last test on an H4 with a 100/2.2 gave very good 3-meter AF, and mediocre long-distance AF in twilight.
No problem believing Mark about landscape, but I'll believe him about beauty or runway when he has published beauty or runway.
Edmund
Hi,
On the other hand Mark has shimmed his Alpa back within 10 microns, has a special focusing ring that takes three turns to cover the focusing range and uses a laser rangefinder from Leica, AFAIK, so he knows a few things about focusing.
My own view? In my view live view is optimum.
Best regards
Erik
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I have all the S2 lenses and have worked with two different bodies. I simply have not had the problems Lloyd has had. Maybe I have been lucky but my recent trip to China using it as a 'travel' camera yielded excellent results. Or maybe people who own the camera are just more familiar with it than Lloyd and have learned to work with it in real situations better than he. All cameras have their idiosyncrasies and no camera is perfect - it's just that I just have no trouble getting sharp images with the S2. I guess YMMV.
Erik, I can't say I have first hand experience with the S2 (other than fondling one lovingly in the camera store) on a shoot; so I am certainly not qualified to make a judgement on the S2 focusing. I have to take the word of Nick, Mark and Lloyd in relation to the S2.
What I would say is that Lloyd is the only one of the bunch to actually have made public an extensive test on the S2 in relation to focusing. And that carries more weight for me than flowery statements like 'deadly accurate'.
I suspect (and only suspect) that perhaps Mark finds the S2 'deadly accurate' because he doesn't shoot with high end DSLR's - which really are without question at the top of the 'deadly accurate' focus heap. Mark's dslr equivalent is a micro Panasonic isn't it? (I think thats what he took to Africa when he wrote up his return editorial - I would have to go back to be 100% certain) Not exactly top end auto focus compared to a 1D MKIV or Nikon D3S. I wonder if his 'deadly accurate' statement is more born out what he is used to shooting, rather than what really rules the roost in terms of auto focus.
I would really like to see some more s2 focus testing - its still very high on my list for purchase consideration. Really, I should just go borrow one and shoot over a weekend with it. Perhaps when more lenses become available ;D
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I have all the S2 lenses and have worked with two different bodies. I simply have not had the problems Lloyd has had. Maybe I have been lucky but my recent trip to China using it as a 'travel' camera yielded excellent results. Or maybe people who own the camera are just more familiar with it than Lloyd and have learned to work with it in real situations better than he. All cameras have their idiosyncrasies and no camera is perfect - it's just that I just have no trouble getting sharp images with the S2. I guess YMMV.
I got reports of a landscape test here in Paris which indicated the same infinity focus issues as Lloyd found. Lloyd is a landscape guy basically, so I would respect him when he talks about landscape; he doesn't bother with stuff like focus speed and focus target discrimination, which is what SLR focus is all about, but then landscapes don't usually run away or wave their arms.
Edmund
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Hi,
I don't know...
Nick Devlin and Mark Dubovoy don't have a similar experience. I have great respect for Lloyd's testing, and he has images to show. On the other hand I also have great respect for Nick's and Mark's testing.
Best regards
Erik
I agree with what you are saying and I'll add that I never get the feeling from Lloyd's reports that he's selling anything. I've had issue with Mark's multishot review, Imageprint review, and several others - maybe half had statements that I felt wouldn't hold up under any 3rd party testing and they always come off as an informercial.
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Hi,
My impression is that Mark is a bit enthusiastic in his reviews. He wants to share experience. I'm pretty sure that he knows what he is doing.
It is not always easy to detect inaccurate focus. To begin with, all sources of image degradation add up. So to judge focus we need to have an absolutely stable setup with mirror lockup and vibration free shutter release. Stopping down reduces the need of focusing accuracy. Normally we strive for maximum image quality and that usually ends in the camera on tripod, MLU and medium aperture formula.
For some reason, Lloyd seems to be interested in shooting at full aperture which is most demanding on optics. This perhaps comes from his testing work.
It is easy to misjudge sharpness, I once tested a camera with and without mirror lockup. All pictures were sharp (at actual pixels). I also measured MTF on slanted edge using Imatest on the same series of exposures. Half the resolution was lost without MLU! Rechecking the images I could see the difference! Halving resolution essentially reduced camera resolution from 6 MP to 1.5 MP, but I could barely see the difference!
Another observation is that Leica plays it very smart. They are good at communicating with customers (or at least reviewers) it seems that Mark got a lot of good information from Leica on the workings of the AF system but he may get far less information from other vendors. The kind of openness Leica seems to have certainly works in their favor.
It would be nice if the departure of Kodak would lead to Leica and Pentax working with a CMOS vendor instead. It is my firm belief that live view is ideal for tripod mounted landscape shooting.
Best regards
Erik
I agree with what you are saying and I'll add that I never get the feeling from Lloyd's reports that he's selling anything. I've had issue with Mark's multishot review, Imageprint review, and several others - maybe half had statements that I felt wouldn't hold up under any 3rd party testing and they always come off as an informercial.
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I can confirm this, he should know a few things about focus.
Thierry
On the other hand Mark has shimmed his Alpa back within 10 microns, has a special focusing ring that takes three turns to cover the focusing range and uses a laser rangefinder from Leica, AFAIK, so he knows a few things about focusing.
Erik
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Hi Ray,
The only measurements I have seen were on DxO-mark. When the 645D arrived I got the impression that it handled read noise really well. My understanding is that DR that DxO-mark measures is dominated by read noise. It is also my understanding that with CCDs analog readout is not integrated on the chip but is on a separate PCB and I got the impression that the Pentax solution is really good. Since than DxO mark republished data on the P40+ and it seems be even better than the Pentax 645D.
I have played around with raw files from Pentax 645D (from Imaging Resource and Miles Hecker) and Leica S2 (with kind permission of Lloyd Chambers) I was not impressed by shadow noise on the S2.
The Leica S2 stuff is here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/38-observations-on-leica-s2-raw-images
The Pentax article is not about DR, but it's here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/51-a-closer-look-at-pentax-645d-image-quality
Your idea on MFD read out noise data base is very interesting. My impression is that MFDBs are surrounded with a lot of mythos, but I guess that only benefit of MFDBs over DSLR sensors is larger size. A larger sensor collects more photons, holds more electron charges and so on. A larger sensor may also have advantage in resolution and allow higher MTF on a given structure size. So no doubt that there are many benefits to MF digital.
Do you have any ideas about sample variation?
Best regards
Erik
Hi Eric,
I'm glad you can see the merit of my MFD read out noise database idea. The first results are coming in, and I will share them in due course. Interesting things are also emerging about how some manufacturers are treating their raw data! :-X
I strongly encourage other MFD shooters to contribute as well. I omitted one instruction in my original post up this thread: without this I can get the noise in ADU, but that's useless unless I can also get the conversion factor to electrons. So the full instructions are:
- Take two frames at each ISO setting, with the lenscap ON, at the shortest shutter speed on your camera
- Take two frames at each ISO setting, with the lenscap OFF: camera on tripod, aimed at a white wall/ceiling, telephoto (or failing that, normal) lens set to f/16 and INFINITY focus, exposure set to give a bright but unsaturated/unclipped image (metered exposure + 1 stop compensation should be about right; check the LCD histogram)
- Put the RAW files on somewhere like Dropbox, where I can download them.
This assumes that the black point is not being clipped by the Manufacturer's firmware. If my initial work reveals that it is being clipped in some cases, I'll have to ask those contributors for some more data (basically the white wall shots again, but this time at a large range of exposure times). I am not asking for that at this stage, as I don't want to put busy people (including myself!) through extra work unless it's really needed.
You raise a good point about sample variation. Here's where strong community involvement can help. If more than one person sends me samples from the same model of camera, we can start to assess variations like this.
Look at it this way - every contributor will get a sort of custom analysis report on their sensor. For free. I'm sure that manufacturers and repair houses would charge a lot for that sort of thing. ;D
Ray
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I can confirm this, he should know a few things about focus.
Thierry
But actually not that much. He has an article here on LL where he states focus tolerance is a product of focal length. Which if you understand the problem, focal length has nothing to do with it. Tolerance is a product of the f-number of the system--regardless of focal length, if focus is off x mm, the amount of defocus is based on the f-number of the system. (Talking about front focus or back focus misses the entire problem as it is an image space issue, not an object space one.) Also in the Mamiya/Pentax shoot out article, he suggests (actually, claims) the the problem with edge sharpness is unaligned sensors--it could not be user error (after all it was two guys doing informal testing) or even the wall might not be flat--not that old buildings are not level and plumb. Occam's razor would throw that conclusion into doubt. And he shimmed his back 10 microns? Exactly what back is he using that would have a 2 micron CoC, assuming he is shooting at about f/4.5.
I would not consider this gentleman a great authority on focus.
From what I understand, Mr. Chambers is a pixel peeper. There are real flaws with evaluating images at 100%.
The problem I find with many reviews/claims is that they are extreme. That every slight flaw or perceived flaw (found in single samples most of the time) are grossly exaggerated.
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Ray,
What more are you testing than DxO? They have results for all the major MFDB's; and a related website
http://www.sensorgen.info/
converts DxO results into more standard figures of merit for sensor performance (this site only analyzes a few MFDB's but gives details on how to extract the numbers from DxO data).
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Emil,
First of all, DxOmark have actually only tested a small minority of recent/current MFDBs/MFDSLRs. And they show no inclination to test any older models; only some new releases. But people keep using the old ones; they have greater longevity, both physically and in terms of desirability, than DSLRs. And second-hand older ones are the usual entry point for MFD among amateurs, etc. We deserve to know how these units perform, too.
I am indeed aware of sensorgen.info. It's a brilliant idea, with tremendously useful information (I go to it sooner than I go to DxOmark). But it is a bit limited in what it tells you, because it inherits DxOmark's limitations.
Here are a few extra things that my tests will address:
- DxOmark/Sensorgen do not tell you about how many bits of data are actually used.
- They do not tell you about raw manipulation, like zero clipping.
- They do not give the gain/ADU at the different ISOs [this could probably be worked out from their data, however]
- They do not give any indication of dark current / long exposure performance (I'm not addressing that yet, but intend to do so in time, as it's hugely important in MFD)
- They do not give any indication of sample variance from unit to unit.
- They do not give any indication of count/percentage of defective pixels (again, that won't be my focus initially, but it's there to be seen in the data)
- There are also strange anomalies in some DxOmark/Sensorgen measurements, which need further independent investigation. For example, look at the Pentax 645D in Sensorgen: why does the readnoise suddenly jump up, apparently almost double, in going from ISO 800 to 1600?! (And the less said about the Nikon D3100's readnoise of "0.0 electrons", the better!)
Ray
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Hi,
I absolutely agree that there is much misunderstanding about focusing accuracy, especially regarding image space. I wanted to write an article on the issue but I lack the necessary drawing and pedagogic skills.
Regarding Mark Dubovoys shimmming of the digital back to ten microns, he has posted sample images on the issue and they clearly indicate the importance of shimming. The digital back he is using is the Phase One IQ180 (I think) having a sensor pitch of 5.2 microns and lenses from Alpa, probably based on Schneider Digitars and Rodenstock HR Digarons. Both series of lenses being very good. I agree with your view that 10 microns of misalignment would need a 2.5 micron pitch sensor to detect using f/4.
I have made some series of exposures with different amounts of defocus on an Sony Alpha A55 with 4.77 micron sensor pitch and found that a CoC of 6.3 microns on that sensor causes clearly visible loss of sharpness.
Correct focus (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-5.jpg)
Defocused (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-6.jpg)
Camera moved 3 cm at object distance of 3.00 m, f=100 mm aperture = f/5.6.
Full article is here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/49-dof-in-digital-pictures?start=1
I'd also like to point out that you may perhaps confuse some gentlemen. The author shimming the back on the Alpa was Mark Dubovoy while 645D lens/sensor alignment issues were discussed by Nick Devlin and Mark Segal.
I admit that examining images at actual pixels is pixel peeping, but it is the only way to actually judge image quality. Why would you spend tens of thousands of Dollars on pixels if you are throwing away 75% of them?! Admittedly, often those pixels may not be needed, sometimes it's hard to see differences between 12 MP and 24 MP in A2 prints (16"x23").
I'm mostly shooting with a Sony Alpha 900, and I normally don't see focusing issues when using AF in a careful way, but I mostly use f/8 and that may mask some focusing errors.
Best regards
Erik
But actually not that much. He has an article here on LL where he states focus tolerance is a product of focal length. Which if you understand the problem, focal length has nothing to do with it. Tolerance is a product of the f-number of the system--regardless of focal length, if focus is off x mm, the amount of defocus is based on the f-number of the system. (Talking about front focus or back focus misses the entire problem as it is an image space issue, not an object space one.) Also in the Mamiya/Pentax shoot out article, he suggests (actually, claims) the the problem with edge sharpness is unaligned sensors--it could not be user error (after all it was two guys doing informal testing) or even the wall might not be flat--not that old buildings are not level and plumb. Occam's razor would throw that conclusion into doubt. And he shimmed his back 10 microns? Exactly what back is he using that would have a 2 micron CoC, assuming he is shooting at about f/4.5.
I would not consider this gentleman a great authority on focus.
From what I understand, Mr. Chambers is a pixel peeper. There are real flaws with evaluating images at 100%.
The problem I find with many reviews/claims is that they are extreme. That every slight flaw or perceived flaw (found in single samples most of the time) are grossly exaggerated.