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Author Topic: Got my hands on the new Pentax 654Z today...  (Read 23954 times)

weinlamm

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Re: Got my hands on the new Pentax 654Z today...
« Reply #20 on: June 22, 2014, 02:28:54 pm »

Mine lives on a tripod. The ISO could be fixed at 12 (like the first version of Kodachrome my dad used in the 1950s) and it wouldn't make much difference in how I use it.   :D

-Dave-

If you want a camera with Iso12 you perhaps need to buy an old Kodak DCS/n or /c. I can remember, that you could use there this Iso for long exposures.  :)
Ok. It's 35mm and not MF...  ::)
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Telecaster

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Re: Got my hands on the new Pentax 654Z today...
« Reply #21 on: June 22, 2014, 11:01:40 pm »

If you want a camera with Iso12 you perhaps need to buy an old Kodak DCS/n or /c. I can remember, that you could use there this Iso for long exposures.  :)

The Contax N Digital also had a low-ISO mode, something like 25 if I remember right. I think noise reduction was the primary intent.

With the 645D I've had no need for anything slower than ISO 100 but I do own some ND filters...   ;)

-Dave-
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torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #22 on: June 23, 2014, 06:17:40 am »

who cares - just use the IQ250 or H matrix - lenses probably account for at least as much divergence of colors from the naked sensor spectral response as a filter difference. Let's just hope that UV and IR filtration are adequate.

Yep you're probably right. As an experiment I have converted the Pentax 645Z DNG file to a Phase One IIQ IQ250 file and opened it in Capture One just to see how it renders (as Capture One thinks it's an IQ250 file it renders the raw data exactly as if the image was shot with an IQ250 rather than a 645Z), and to my untrained eye color looks good, a bit saturated but nice skin tones. So if there is any divergence is certainly not huge.

I've done the same experiment with a Hasselblad H5D-50c file, and that too turned out well, so probably the differences in color response between those three cameras is very very small, and as you say lenses could be the largest part in any differences. The difference in color is certainly smaller than the difference in price ;D
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Doug Peterson

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Re: Got my hands on the new Pentax 654Z today...
« Reply #23 on: June 23, 2014, 07:11:42 am »

Yep you're probably right. As an experiment I have converted the Pentax 645Z DNG file to a Phase One IIQ IQ250 file and opened it in Capture One just to see how it renders (as Capture One thinks it's an IQ250 file it renders the raw data exactly as if the image was shot with an IQ250 rather than a 645Z), and to my untrained eye color looks good, a bit saturated but nice skin tones. So if there is any divergence is certainly not huge.

I've done the same experiment with a Hasselblad H5D-50c file, and that too turned out well, so probably the differences in color response between those three cameras is very very small, and as you say lenses could be the largest part in any differences. The difference in color is certainly smaller than the difference in price ;D

Color is a lot more complicated than is indicated by the level of experimentation you made before making such strong conclusions. Have you done this under multiple illuminates? Have you done this with dozens of people with different variations of skin? Have you done this with under and over exposed images with appropriate recovery? Have you examined product color for linearity of color throughout the tonal range?

My *initial* examination of the IQ250 color took several weeks and I won't feel I know it's color response as well as I do for backs like the IQ160 (which I've simply had more total shoots with) for many more months.

Cameras with excellent color are robust in color response; they look great even under duress.

It's odd because I'd never imagine you making such strong conclusions about noise, or sharpness with such minimal testing.

torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #24 on: June 23, 2014, 07:23:14 am »

It's odd because I'd never imagine you making such strong conclusions about noise, or sharpness with such minimal testing.

I dare to do that based on that I know it's the same sensor, and that a CMOS which has digital output rather than analog like CCD is much less affected by surrounding electronics.

But it's just a fun experiment with a test software only I have. The general photographer can't and wouldn't convert Hasselblad and Pentax files into IQ250 files, and of these three cameras only the IQ250 can be used with Capture One. I think Capture One is a very important link in the great color rendition reputation Phase One has.

Even if these three cameras have the exact same color response, the raw converter softwares are different and color profiles are different so results will be different. So Phase One don't need to worry just yet :).

This experiment is a "what if" experiment showing what would happen if all these cameras had the same raw converter and color profiles. And the indication I have is that it will then render very similar results (which is the expectation when knowing about the hardware), but you're right that it's early to come to the safe conclusion, shooting all three cameras on a large color checker under the same light and do measurements on that would be required to draw safe conclusions.

To be perfectly honest what I see is good color, as I don't have a reference file from an IQ250 shot at the same place I cannot know for sure if the IQ250 would render the same scene with good color in a radically different way, I just find that unlikely.

At some point I hope someone will actually make side-by-side shooting and provide raw files so I can convert them all to IIQ (open them in RawTherapee and use same profiles will also work) so one can directly compare how the hardware performs. There's a bunch of mythology around the superiority of Phase One hardware some true some less so, and this type of test would be revealing in that aspect. However for real use it makes little difference and you need to take the whole pipeline into account. It will be Pentax + Lightroom(?) vs IQ250 + Capture One vs Hasselblad + Phocus/Lightroom. And I think for portrait style of work that Capture One will have an edge. And of course we have the lens parameter too, which I'm uncertain about how much effect it has.
« Last Edit: June 23, 2014, 07:37:49 am by torger »
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Ken R

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Re: Got my hands on the new Pentax 654Z today...
« Reply #25 on: June 23, 2014, 08:55:32 am »

Even though the Sony A7R and the D800E have a basically identical sensor the image quality and performance is not identical. So that is just one example of two cameras with the same sensor performing differently. Ok, the differences are not major but are there.

And again, I see the undertone, that the IQ250 is not a good value. Of course it isn't (once the 645Z is out, available and tested) in sensor image quality per dollar terms but it offers something different. It is a back that can be used in a LOT of different camera systems with lot's of different lenses. Yes, that has a price, but is something the 645z just can't do and the H5D-50c can do in limited capacity (no untethered live view, crappy lcd screen etc).

That out of the way it would be cool to see tests and comparisons between all three 50mp CMOS cameras (H5D-50c. 645Z and the IQ250)
« Last Edit: June 23, 2014, 09:01:18 am by Ken R »
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torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #26 on: June 23, 2014, 10:25:26 am »

The A7r and D800E has documented CFA differences (you can see scientific measurements on DxOmark).

I don't rule out that there are CFA differences here too, need side-by-side controlled testing to make sure. Sometimes CFA can be quite different and color still look good if you switch profiles.

Anyway this is the first time(?) we see three cameras with these type of price differences using the same sensor. I find it very interesting to know exactly how much that is the same.

It could be the case that the Pentax 645Z still would use some high ISO optimized CFA (like most DSLRs is said to do) and render skin tones worse due to the hardware. It could also be the case that the CFAs are exactly the same and the exact same result with minor differences caused by lenses can be had if applying the same profiles.

I imagine that Phase One owners are not so interested in such an investigation, but people that look into buying the 645Z to get into MF in an affordable way probably are. At least I would then like to know if I get a "true" MF camera with MF optimizations concerning color, or if I just get an enlarged DSLR, and ugly too.
« Last Edit: June 23, 2014, 10:28:41 am by torger »
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eronald

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Re: Got my hands on the new Pentax 654Z today...
« Reply #27 on: June 23, 2014, 11:01:09 am »

Doug,

 Yes, it would be possible that P1 and H and Pentax are using the chip differently, and in particular when it come to data in the highlight shoulders or extreme shadows one might see real differences. But Torger does have a point when he considers that the essential ability of the camera to discriminate color is intrinsically defined and delimited by the CFAs and the IR and UV filtration. This is an inherent weakness of the Bayer CFA model, and you cannot magically make it go away: The CFAs never match the human eye's response (cone or observer functions) and thus cameras do not see like the human eye.  The camera's ability to discriminate *texture* ie. skin texture is a different story as it will depend on the signal processing.  

Edmund

PS: It is an INCONVENIENT TRUTH that cameras using the same CMOS chip with the same CFA and the same on-sensor A/D conversion are quite possibly going to have very similar imaging behavior. Unfortuntately, Phase 1 were never a camera company, they have been a back company, and if they buy in a complete-solution chip they lose differentiation. Please don't blame the geeks for stating and experimentally confirming the obvious.

Color is a lot more complicated than is indicated by the level of experimentation you made before making such strong conclusions. Have you done this under multiple illuminates? Have you done this with dozens of people with different variations of skin? Have you done this with under and over exposed images with appropriate recovery? Have you examined product color for linearity of color throughout the tonal range?

My *initial* examination of the IQ250 color took several weeks and I won't feel I know it's color response as well as I do for backs like the IQ160 (which I've simply had more total shoots with) for many more months.

Cameras with excellent color are robust in color response; they look great even under duress.

It's odd because I'd never imagine you making such strong conclusions about noise, or sharpness with such minimal testing.
« Last Edit: June 25, 2014, 03:34:46 am by eronald »
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torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #28 on: June 23, 2014, 01:02:37 pm »

I got permission to show the file by the anonymous photographer that I got the test file from. That photographer was at the same testing event as johnvr as obvious from the model but it's not him I got the file from. It's a test file useful for testing format support with a color checker in focus so it's not exactly a good example of imaging performance, but it does show skin color and gives a general idea of saturation etc.

Note that the white balance is crazy, it's that also in the original Pentax DNG, so it probably just was some camera setting that was off. Just use the wb pipette on the color checker to restore a sane white balance.

So here's how a Pentax 645Z file raw data looks if it's rendered the same way as an IQ250:

edit, link removed too many downloads :), but anyone really interested just send me a PM

If someone wants me to convert another file for testing just send me one. One with the model actually in focus would be cool I guess :)

(The reason I've made IIQ writer is not for these type of conversions, but for Phase One owners to be able to use our Lumariver HDR software in a raw in to raw out workflow, Capture One's DNG support is not exactly great. The version with IIQ support is still in the making.)
« Last Edit: June 23, 2014, 06:23:41 pm by torger »
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PdF

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Re: Got my hands on the new Pentax 654Z today...
« Reply #29 on: June 25, 2014, 03:29:58 am »

Mine lives on a tripod. The ISO could be fixed at 12 (like the first version of Kodachrome my dad used in the 1950s) and it wouldn't make much difference in how I use it.   :D

-Dave-

I agree. For the work that is mine (studio), a very low sensitivity is an asset. This allows to work in the best conditions (choice of f-stop) with flash. In the studio today, it is often necessary to have to work with a too small aperture.

PdF
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torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #30 on: June 25, 2014, 04:07:59 am »

I agree. For the work that is mine (studio), a very low sensitivity is an asset. This allows to work in the best conditions (choice of f-stop) with flash. In the studio today, it is often necessary to have to work with a too small aperture.

Uhm, couldn't you just use an ND filter?

Low sensitivity in digital photography is unfortunately generally not implemented the way one would like, ie that you have a huuuuuge collector of photons that just takes a very long time to fill up. Rather, in digital low sensitivity generally means that the sensor only registers a part of the light and throws away the rest, due to low fill factor (fill factor = how much of the sensor area that actually registers light) and/or inefficient micro lenses (micro lenses are used to direct light into the light-sensitive photo diodes).
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ErikKaffehr

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Re: Got my hands on the new Pentax 654Z today...
« Reply #31 on: June 25, 2014, 08:14:03 am »

Hi,

I don't know about the data DxOmark publishes, they publish the color conversion matrixes, RGB channel sensivities and SMI for two illuminants. Regarding SMI I have seen that Tim Parkin feels it correlates well with color rendition, while Iliah Borg seems to say it is irrelevant.

For my part, I am not sure DSLR CFAs are optimized for high ISO. The best optimisation for high ISO is low readout noise and fat pixels. The P45+ I happen to have is one of the worst sensors regarding SMI.

I am a bit reserved about basing colour accuracy on just the color checker fields. I have made some additional tests on an IT80 card and found that the P45+ was pretty accurate, specially with Capture One and linear profile. But my Sony Alpha 99 was still a bit more accurate.

To me it seems that there may be a lot of myths about the accuracy of MFD colours. It may also be that there is no real good definition of good skin colour, many MFD images shown have highly artificial skin tones. I would think it could be that MFD color profiles are a bit tweaked for what is regarded good skin tones,especially under studio conditions.

My experience is limited to Sony cameras and a single P45+.

Best regards
Erik

The A7r and D800E has documented CFA differences (you can see scientific measurements on DxOmark).

I don't rule out that there are CFA differences here too, need side-by-side controlled testing to make sure. Sometimes CFA can be quite different and color still look good if you switch profiles.

Anyway this is the first time(?) we see three cameras with these type of price differences using the same sensor. I find it very interesting to know exactly how much that is the same.

It could be the case that the Pentax 645Z still would use some high ISO optimized CFA (like most DSLRs is said to do) and render skin tones worse due to the hardware. It could also be the case that the CFAs are exactly the same and the exact same result with minor differences caused by lenses can be had if applying the same profiles.

I imagine that Phase One owners are not so interested in such an investigation, but people that look into buying the 645Z to get into MF in an affordable way probably are. At least I would then like to know if I get a "true" MF camera with MF optimizations concerning color, or if I just get an enlarged DSLR, and ugly too.
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torger

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Re: Got my hands on the new Pentax 654Z today...
« Reply #32 on: June 25, 2014, 09:07:10 am »

I think few talk in terms about "accuracy", but rather pleasing or film-like or some other hazy concept. I'm too a bit skeptical about it, therefore I think it's an interesting experiment to cross-convert H5D-50c, Pentax 645Z so they all can be compared with an IQ250 type of rendering. If equivalent or at least pleasing results can be had we at least know that differences can be equalized with profiling.

I'm a bit surprised that there are not more third-party profiles, it seems like many photographers are willing to spend say $20k extra for a camera because they don't really know how to get good results of lower cost competing systems.

I will expect that 1) Pentax 645Z will not be supported by Capture One (I would not do it if I were Phase One), 2) color profiles in Lightroom or Pentax own software will not produce as pleasing results as MF portrait photographers want, and IQ250 results will be considered superior, and 3) many will claim it's due to the hardware, and that $15-20k extra you get to spend for it is what's required to get the best color, 4) few will investigate if it's possible to tune profiles for the Pentax to get as good results.

I think MF needs competition, their business model which is what makes the products so insanely expensive is ancient and need to change, and Pentax 645Z is a dynamic contribution to the market and I very much would like to see it become a success. I don't wish any bad luck onto Phase One or Hasselblad, but I don't think they will ever change their business model unless there's some pressure put on them, and someone else (ie Pentax) shows that you can make money by selling lower cost to a broader market.
« Last Edit: June 25, 2014, 09:10:02 am by torger »
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eronald

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Re: Got my hands on the new Pentax 654Z today...
« Reply #33 on: June 25, 2014, 10:47:17 am »

well, as Hassy's main client base is fashion, I don't think they will allow their skin tones to get too bad :)

skin tone are a mix of color and texture. color depends on the CFAs except in extreme shadows and highlights where camera firmware affects antiblooming settings (top shoulder) and channel noise removal (bottom clipping). Texture depends on firmware filtering and the raw converter.


anyway, I would expect the CMOS MF sensors from Sony to track the 35mm cameras from Sony pretty exactly when it comes to color.


Edmund

PS. Note that there is nothing to prevent a camera from loading new firmware with different characteristics to switch from architecture to portrait, eg. shadow noise filtering vs more noisy and harder hilite clipping, but manufacturers have not done this so far. 

I think few talk in terms about "accuracy", but rather pleasing or film-like or some other hazy concept. I'm too a bit skeptical about it, therefore I think it's an interesting experiment to cross-convert H5D-50c, Pentax 645Z so they all can be compared with an IQ250 type of rendering. If equivalent or at least pleasing results can be had we at least know that differences can be equalized with profiling.

I'm a bit surprised that there are not more third-party profiles, it seems like many photographers are willing to spend say $20k extra for a camera because they don't really know how to get good results of lower cost competing systems.

I will expect that 1) Pentax 645Z will not be supported by Capture One (I would not do it if I were Phase One), 2) color profiles in Lightroom or Pentax own software will not produce as pleasing results as MF portrait photographers want, and IQ250 results will be considered superior, and 3) many will claim it's due to the hardware, and that $15-20k extra you get to spend for it is what's required to get the best color, 4) few will investigate if it's possible to tune profiles for the Pentax to get as good results.

I think MF needs competition, their business model which is what makes the products so insanely expensive is ancient and need to change, and Pentax 645Z is a dynamic contribution to the market and I very much would like to see it become a success. I don't wish any bad luck onto Phase One or Hasselblad, but I don't think they will ever change their business model unless there's some pressure put on them, and someone else (ie Pentax) shows that you can make money by selling lower cost to a broader market.
« Last Edit: June 25, 2014, 10:56:24 am by eronald »
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AldoMurillo

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Re: Got my hands on the new Pentax 654Z today...
« Reply #34 on: June 25, 2014, 11:10:14 am »

I just saw these high ISO samples from Ming Thein.  To my eyes I can easily use ISO 12800, it opens a lot of posibilities.

https://www.flickr.com/photos/mingthein/14495613532/in/photostream/
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PdF

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Re: Got my hands on the new Pentax 654Z today...
« Reply #35 on: June 25, 2014, 05:15:23 pm »

Uhm, couldn't you just use an ND filter?

When I try to have the best available definition, this is not interposing any filter that will rot my image. And the live video can be found useless ...

PdF
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ErikKaffehr

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Re: Got my hands on the new Pentax 654Z today...
« Reply #36 on: June 25, 2014, 05:37:20 pm »

?

A good filter will not affect the image significantly, and live view works very well with ND filters.

Best regards
Erik

When I try to have the best available definition, this is not interposing any filter that will rot my image. And the live video can be found useless ...

PdF
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PdF

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Re: Got my hands on the new Pentax 654Z today...
« Reply #37 on: June 25, 2014, 06:40:03 pm »

?

A good filter will not affect the image significantly, and live view works very well with ND filters.

Best regards
Erik


Just try it. A good 2ND or 3ND. Look at the quality of your live image in a low lighting with such an equipment.

PdF
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ErikKaffehr

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Re: Got my hands on the new Pentax 654Z today...
« Reply #38 on: June 25, 2014, 07:18:45 pm »

Hi,

I use either 8X or a Kenko variable NDX, never had problem with live view on the Sony, but I don't use ND filters in really low light as they are not needed for the exposures I want to achieve.

The Pentax 645Z sensor is a Sony Exmoor, so it would behave as mine.

Anyway, as Anders Torger pointed out, low ISO is not very feasible on digital sensors. The lowest ISO is on the IQ280 and around 35 (measured), I believe, going below that you need ND anyway.

Best regards
Erik

Just try it. A good 2ND or 3ND. Look at the quality of your live image in a low lighting with such an equipment.

PdF
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ErikKaffehr

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Re: Got my hands on the new Pentax 654Z today...
« Reply #39 on: June 25, 2014, 09:00:01 pm »

Hi,

I see your reasoning.

Just adding a few points:

  • I am not sure lenses affect color rendition that much because I would guess lens colour shift will be mostly well taken care of by choosing white balance.
  • Regarding tuned profiles, I would presume that it takes a lot of experience to fix a pleasant profile and I guess the 'image professor' at Phase One is very good at it.

I compared the normal studio flash profile for my P45+ with the portrait profile, and they are very, very close. As far as I can recall the DeltaE just differed about 1.0 on an IT8 test target. So those profiles are very subtle work.

Best regards
Erik
I dare to do that based on that I know it's the same sensor, and that a CMOS which has digital output rather than analog like CCD is much less affected by surrounding electronics.

But it's just a fun experiment with a test software only I have. The general photographer can't and wouldn't convert Hasselblad and Pentax files into IQ250 files, and of these three cameras only the IQ250 can be used with Capture One. I think Capture One is a very important link in the great color rendition reputation Phase One has.

Even if these three cameras have the exact same color response, the raw converter softwares are different and color profiles are different so results will be different. So Phase One don't need to worry just yet :).

This experiment is a "what if" experiment showing what would happen if all these cameras had the same raw converter and color profiles. And the indication I have is that it will then render very similar results (which is the expectation when knowing about the hardware), but you're right that it's early to come to the safe conclusion, shooting all three cameras on a large color checker under the same light and do measurements on that would be required to draw safe conclusions.

To be perfectly honest what I see is good color, as I don't have a reference file from an IQ250 shot at the same place I cannot know for sure if the IQ250 would render the same scene with good color in a radically different way, I just find that unlikely.

At some point I hope someone will actually make side-by-side shooting and provide raw files so I can convert them all to IIQ (open them in RawTherapee and use same profiles will also work) so one can directly compare how the hardware performs. There's a bunch of mythology around the superiority of Phase One hardware some true some less so, and this type of test would be revealing in that aspect. However for real use it makes little difference and you need to take the whole pipeline into account. It will be Pentax + Lightroom(?) vs IQ250 + Capture One vs Hasselblad + Phocus/Lightroom. And I think for portrait style of work that Capture One will have an edge. And of course we have the lens parameter too, which I'm uncertain about how much effect it has.
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