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09-19-2015, 11:30 AM - 5 Likes   #1
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DxO Labs to add PENTAX 645 Digital System to it's scope

Hi all PENTAX digital medium format shooters or interested observers !


DxO Labs have just completed sensors and lenses tests of PENTAX 645 system.

Corrections will be soon made available for 645D and 645Z RAW files in DxO Optics Pro 10 software, at least for these 12 lenses :

SMC PENTAX-D FA 645 25mm F4 ED AL [IF] SDM AW
SMC PENTAX-FA 645 35mm f/3.5 AL [IF]
HD PENTAX-DA 645 28-45mm F4.5 ED AW SR
SMC PENTAX-D FA 645 55mm F2.8 AL [IF] SDM AW
SMC PENTAX-FA 645 45-85mm f/4.5
SMC PENTAX-FA 645 75mm F2.8
SMC PENTAX-FA 645 80-160mm f/4.5
HD PENTAX-D FA 645 90mm f/2.8 Macro ED AW SR
SMC PENTAX-FA 645 120mm f/4 Macro
SMC PENTAX-A 645 135mm f/4 LS
SMC PENTAX-FA 645 150mm f/2.8 [IF]
SMC PENTAX-FA* 645 300mm f/4 ED [IF]


In addition, DxO Mark sensor data concerning those two bodies will be published.

I guess everything should be available in the forthcomming weeks.





Last edited by Zygonyx; 09-20-2015 at 03:42 AM.
09-19-2015, 12:05 PM   #2
ogl
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Such info is for Pentax 645 digital MF forum or for software section. IMO

Last edited by ogl; 09-20-2015 at 04:04 AM.
09-19-2015, 12:59 PM   #3
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Well, a former thread like this one re. K-3II stayed in that section, but i don't mind.
09-19-2015, 02:33 PM   #4
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No Ogl, here is the place it is meant to be.

09-23-2015, 09:34 AM   #5
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Hi, due to absence of reliable exif data in the lens chip (f=0mm and only a generic "A" line ID), DxO are unable to validate my leaf-shutter beast :

QuoteOriginally posted by Zygonyx Quote
SMC PENTAX-A 645 135mm f/4 LS
Too bad because this is really a very compact and excellent performer imho.
But also wouldn't need much corrections.
09-23-2015, 11:33 AM   #6
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I can't wait to see the dynamic range figures for the Z, they should almost be through the roof compared to other cameras... not that I really need any validation based on the fact that I already own one. Still, the nerd in me desires to know if this camera has a mythical 15 stops or not.
09-24-2015, 02:00 PM   #7
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QuoteOriginally posted by Kolor-Pikker Quote
I can't wait to see the dynamic range figures for the Z, they should almost be through the roof compared to other cameras.
It will be interesting indeed.
But don't bed on it.
645Z at ISO100 and D810 at ISO64 are almost the same, after equivalence normalization. Should be a tight finish, nothing like through the roof to be expected.
09-25-2015, 12:58 AM   #8
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QuoteOriginally posted by falconeye Quote
It will be interesting indeed.
But don't bed on it.
645Z at ISO100 and D810 at ISO64 are almost the same, after equivalence normalization. Should be a tight finish, nothing like through the roof to be expected.
The DR could be similar, but ISO64 is nearly double the exposure time of ISO100. It's kind of like how Phase One hit around 13 stops or so for the first time with the IQ180, but that required you to shoot at ISO35, translating to a much slower shutter or wider aperture needed to maintain identical exposure to something like a D800.

It makes sense to use equal ISO when comparing DR, as people would be willing to sacrifice shutter speed or aperture only so much for a lower ISO, outside of cases where you're shooting still subjects on a tripod.

09-25-2015, 03:05 PM   #9
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QuoteOriginally posted by Kolor-Pikker Quote
It makes sense to use equal ISO when comparing DR,
How many more times does one have to explain equivalency?

No, it does not make sense.

First, for DR you always compare at base ISO.
Second, for the same shutter speed, you stop down more (the larger sensor camera) using higher ISO -- as it yields the same image. There is no sacrifice.

Moreover, MF cameras simply don't have the low fstop lenses FF cameras do. E.g., no MF camera can touch a D810 with an Otus F1.4 lens.

Third, AFAIK, Phase One never had an ISO 35 camera. They use a multi shot feature which is an entirely different beast. My Sony RX100m3 can combine up to 256 shots into a single ISO 2 raw (in 35mm-equivalent terms) with incredible DR. Still, I would never compare that to base ISO performance.
09-26-2015, 08:14 AM - 1 Like   #10
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QuoteOriginally posted by falconeye Quote
First, for DR you always compare at base ISO.
There is nothing that says that ISO100 is the base ISO of the 645Z or that ISO64 is the base of the D810, these are simply the values that the camera engineers have set as the lowest possible. Both use the exact same sensor technology on different scales, there is no reason that Pentax couldn't have given the Z an ISO64 pull.

QuoteQuote:
Second, for the same shutter speed, you stop down more (the larger sensor camera) using higher ISO -- as it yields the same image. There is no sacrifice.

Moreover, MF cameras simply don't have the low fstop lenses FF cameras do. E.g., no MF camera can touch a D810 with an Otus F1.4 lens.
DxO compares the quality of the pixels themselves, detached from the rest of the camera system, there is no equivalency to speak of. Either a pixel has a greater dynamic range than another or it doesn't.
Moreover, it could be argued that for the purposes of where greater dynamic range matters (landscape and architecture), shutter speed and aperture are available to set freely regardless of ISO, so it doesn't matter even in a practical setting, as I wouldn't be shooting a landscape at f/1.4 on any camera.

QuoteQuote:
Third, AFAIK, Phase One never had an ISO 35 camera. They use a multi shot feature which is an entirely different beast. My Sony RX100m3 can combine up to 256 shots into a single ISO 2 raw (in 35mm-equivalent terms) with incredible DR. Still, I would never compare that to base ISO performance.
Yes they do - it's called the IQ180, just as I said in my post, as well as the IQ280 and IQ380, they all have an ISO35 mode which is the only way to achieve maximum DR on any of those backs. Other models such as the IQx60 series only go down to ISO50.
09-26-2015, 02:41 PM   #11
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QuoteOriginally posted by Kolor-Pikker Quote
There is nothing that says that ISO100 is the base ISO of the 645Z or that ISO64 is the base of the D810, these are simply the values that the camera engineers have set as the lowest possible. Both use the exact same sensor technology on different scales, there is no reason that Pentax couldn't have given the Z an ISO64 pull.
[...]
I wouldn't be shooting a landscape at f/1.4 on any camera.
The marketing base ISO may be arbitrary, the measured one is not. DxO confirmed the D810 got a more sophisticated sensor with significantly larger full well capacity than D800 (and likely 645Z too). 645Z and D810 do NOT use the same pixel architecture. This translates to a lower measured base ISO and higher DR. And is the reason why D810 vs. 645Z will be a close race wrt DR.
[...]
If you ignore F-stop equivalency and alike for landscape photography, you are thrown back to base ISO DR as your only metrics anyway.
09-29-2015, 02:14 PM   #12
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All of this, look funny to me honestly.

Eyes can see more than 20EV, true. But a typicall screen provide 9-10EV. Typical paper is 6-8 EV. The display device just do not follow. Of course some screens are capable of displaying more than 10EV but there no format to represent such data right now so this doesn't really work.

If the scenes are static as apparently it is stated there and so you don't care what is the actual base iso because you have all the time in the world. With all that time hopefully you be able to get a properly exposed shoot that will have anyway more dynamic range that your print or screen.

If you want to do tone mapping, to simulate on the display device that there is more contrast that there actually is by playing with the way human vision works, that called tone mapping. That part of an HDR process. And because you are already on a tripod on still subject, you could as well do some exposure braketing and get all the dynamic range you need.

If you are really without contraints and the tripod can fully work then a basic camera and a pano head + some HDR bracketing is going to give you the best, that your sensor has a bit more pixels or a bit more dynamic range isn't going to change anything in the grand schemes of things.


For sure, this is not in theses kind of cases where it is going to really matter. Reality is that even for landscape objects do move. Clouds, water, vegetation, wildlife, peoples, cars. So you'll need the performance at some reasonnable iso/apperture/shutter speed... So no having the thing at iso 64 isn't as good as if it was at say iso 800, by far. This is important because there experimental sensor without limit in dynamic range, they just count the number of time the photosite is saturated. With such technology you would get infinite dynamic range... Even on a Smartphone. So nobody will care what the outdated D810 or 645Z would have been capable of at iso 100 or 64... Because iso 1 would be directly possible with 6-7 more EV or dynamic range.
09-30-2015, 03:17 PM   #13
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QuoteOriginally posted by Nicolas06 Quote
Eyes can see more than 20EV, true.
No, the human eye can't.

What the eye does is adapt its sensitivity when looking around, adapting iris (fast) and the chemical retina process (slow). A camera does the same, it does have an aperture too.

A camera easily outperforms the human eye. Easily observed when blinded by upcoming car headlights. While a Sony sensor would still capture a dark subject next to it, the eye fails at that.

If we would have display devices exceeding 8 EV contrast with a lot of image data in the dark parts, we would actually be blinded by the brighter parts and watching TV would become annoying.
10-01-2015, 12:12 AM   #14
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QuoteOriginally posted by falconeye Quote
No, the human eye can't.

What the eye does is adapt its sensitivity when looking around, adapting iris (fast) and the chemical retina process (slow). A camera does the same, it does have an aperture too.

A camera easily outperforms the human eye. Easily observed when blinded by upcoming car headlights. While a Sony sensor would still capture a dark subject next to it, the eye fails at that.

If we would have display devices exceeding 8 EV contrast with a lot of image data in the dark parts, we would actually be blinded by the brighter parts and watching TV would become annoying.
TV are typically advertising 1:1000, 1:2000, 1:5000 that 10EV, 11EV, 12EV. Oled has typically infinite contrast and at least 1:20000 so that 14EV. A standard for HDR moving is on the go for 12EV recording to display.

When I look at a sunset and an object in front of it, I'am not able to see the details inside the sun (but the camera can without a filter), but I can see the whole set of colors of the sky and I can still see lot of detail in the first plane subject. Camera need a flash and/or to push shadows and bring in noise. The eyes support more than 20EV.

And yes with time the eyes adapt to different conditions. This mean the same scene the eye can concentrate on one dark subject and just after a bright subject in the same scene. It can change focus. In reality the human will go the flower, smell it, look at it from near distance and 1 second after he will go back to the whole landscape view. It is live, it is reality. A photograph as only one exposure at a time and one focus distance at a time. This is not the same. The camera need to do much more to compensate that it is just one image, it is not reality.
10-01-2015, 05:19 AM   #15
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QuoteOriginally posted by Nicolas06 Quote
TV are typically advertising 1:1000, 1:2000, 1:5000 that 10EV, 11EV, 12EV. Oled has typically infinite contrast and at least 1:20000 so that 14EV. A standard for HDR moving is on the go for 12EV recording to display.
The key point with TV dynamic range lays entirely within the black level. A display can have "infinite" contrast ratio simply by having blacks that are pure black, but our eyes don't get strained by an absence of light. For a display to truly show more than 7 stops DR it would not only have to have a very low rated black level, but a very bright backlight as well, even though in practice though most displays are calibrated to a brightness target that's comfortable for extended viewing regardless of what the display is capable of.

QuoteQuote:
When I look at a sunset and an object in front of it, I'am not able to see the details inside the sun (but the camera can without a filter), but I can see the whole set of colors of the sky and I can still see lot of detail in the first plane subject. Camera need a flash and/or to push shadows and bring in noise. The eyes support more than 20EV.
You're still being mislead by your visual system. Our eyes don't work like photographic nor motion video devices, they continually scan and update an image that's recorded to visual memory. It's impossible or at least not within our conscious control to truly "focus" on something so as not to allow our brains to fill in the blanks. Our eyes move and update various points in space over 200 times a second even when we think we're looking straight-on, and they have to, since only 1% of our visual field is responsible for nearly all of the detail that we see.

The reason you can look at a sunset and see a lot of the tonal range with such small sensors/optics stuck in your face is due to HDR processing occurring along every stop of the way from your eyes to your imagination. And imagination has a lot to do with things, after all, do you know what the color pink is? The near-visible radiation scale begins with ultraviolet and ends with infrared, so where does pink fit in? It's actually a non-existent color your brain makes up in absence of green, so pink is actually "negative green".

Facts concerning the human visual system get increasingly more freaky from here on out as you ask more and more questions, like how do out eyes deal with cloning out all the blood vessels in our eyes, among other things. When you take every factor into account, our visual system is constantly doing one heck of a Photoshop job, essentially taking a bunch of random data from the visual cortex and reconstructing it in a way we can comprehend.

Last edited by Kolor-Pikker; 10-01-2015 at 05:28 AM.
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