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04-14-2021, 02:07 PM - 2 Likes   #46
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There is nothing unique about this phenomenon to the KP or any subset of Pentax DSLRs. The presence of a color filter array and the way that cameras and demosaicing algorithms try to mimic human photopic vision have some significance regarding the prevalence of magenta in these scenarios where every color channel is beginning to fully saturate, but the flare is first and foremost an optical phenomenon that will affect the imaging plane regardless.

The only thing noteworthy about the K-5 line in this context is that their photosites individually have a very high well capacity. Only the 645 DSLRs have more. They are harder to saturate to the point of the intense magenta or completely clipped white, but with overexposure it can be easily mimicked. Likewise, underexpose in the presence of high contrast/backlighting and you will avoid the intense magenta saturation, though in some scenarios a camera may not have the dynamic range for it to be feasible in one exposure.

As for Fuji: the magenta flare is no more specific to them than any camera that uses a filter array. There is an additional phenomenon where coarse(r) grid-like patterns may show in flares due to the arrangement of the X-Trans array, presumably a solvable (if not already solved) problem with changes in demosaicing logic.

QuoteOriginally posted by RICHARD L. Quote
Could the creation of those artefacts depend on the lens you use ? I never see anything like that in my pictures. Here with an HD DFA 28-105 mm @ 28 mm FL and f/11.

QuoteOriginally posted by RICHARD L. Quote
Those artefacts can be created when using poorly coated filters. Modern SMC Pentax lenses as well as 645 and 67 lenses don't flare at all. Staight lenses prove to be very resistant to flare.
They absolutely flare; it is just harder to achieve. See attached images with the HD D FA 28-105 wide open @ 28mm on the K-1. I literally just went outside and shot the sun through a tree. Today is cloudy where I am so this is even more diffuse / less contrasty than it could be.

QuoteOriginally posted by house Quote
As far as I understand the lens has to be wide or you have to provoke flare. I have also heard that ff lenses on crop bodies are more prone as light ends up where it shouldn't be.

Flare means light is bouncing around inside the lens hitting the sensor at angles it wasnt designed to handle.

So yes the lens is a big part of the equation. Presumably sensor stacks micro lenses etc also impact the performance.
Using a lens intended for a larger format is indeed at least an opportunity to invite more errant light into the system. You can even see this in action on the K-1 or K-1 II with the natively designed SMC Pentax 28/3.5 Shift - shift lenses must necessarily cover more area than the format they are designed for. Flares are much easier to achieve than with similarly coated SMC lenses, and hot spots may be more common on the edges of the frame than usual due to the relative lack of vignette on border photosites.

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Last edited by Sykil; 04-14-2021 at 02:57 PM.
04-15-2021, 09:30 AM   #47
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QuoteOriginally posted by stevebrot Quote
Are you referring to a link on this thread or on FB. If on FB, it would be amazingly helpful to simply provide the link. Even searching the group for "campanelli post" failed to bring up a meaningful list of posts.

Steve
Sorry about that. Here you are!

Log into Facebook | Facebook

Thanks
Danilo
04-17-2021, 03:26 PM   #48
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Hi all !
it has been asked whether these problems occurs in the "real world". Please check this post and look at the images I sent:. despite these subjects are not really interesting (I was trying the AF540FGZ flash) please notice the purple area. Noone can say that because by backpack is ugly this is not a real issue. Yes, this is a Pentax KP with smc Pentax D-FA 100mm macro


https://www.facebook.com/groups/2703773516602072/permalink/2729096877403069/

Bye!
Danilo

Last edited by mctaveck; 04-17-2021 at 03:32 PM.
05-03-2021, 05:05 AM   #49
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Hi all,

I end up thinking my KP suffer some sensor issue. What I've been told match with the behaviour of the camera that does not seem to be related to the lens or the setting. Seem this is a sensor blooming. What I've been told is that:

"It is a notorious "sensor blooming": the sensor is responsible: it goes into saturation on the highlights and from the saturation of the photodiodes in high light photons overflow, the blooming is a loss of photons of the sensor, which with the filter Bayer above, then produce purple fringes in the image.
Of course it always does it to you, on photos and movies. (...) It is not a Chromatic Aberration, whether lateral or axial, due to the optics, the optics have no faults, it is a loss of photons from the sensor."


Does it sounds reasonable? To me, since the behaviour of my camera , yes.

Thanks for any technical comment you may add.

Danilo.

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