200ms artifacts with static subjects and continuous light

[Jordan]

Hi,
My 200ms creates tiny magenta and sometimes blue and yellow artifacts in the highlights. I have seen this with both the cmos and ccd sensors now. The sensor looks clean. Is this just a byproduct of the 200ms mode. It doesn't appear in the 50ms mode. Anyone else have this experience? Thanks in advance.

[Alex]

Yep,

Funnily enough though they don't appear when outputted as (linear) DNGs
There's also this thing that sometimes if you UnTick Chromatic corrections in the (Phocus) Lens Corrections that you get less C. Aberrations
...Not to mention that the 6s file preview never shows the Scene Calibration applied correction unless at 100% - very disconcerting - good old Phocus!

Alex

[Jordan]

Hi Alex- thanks for the quick response. I actually get them when I output as DNG.

[Alex]

Achh.. Have you tried the L. DNGs through Iridient?

It's a bit cronky (but if you've used Phocus you'll be in right mindset)

Alex

[Jordan]

I have not. Perhaps I will give that a try. Thank you for your assistance thus far sir

[Alex]

Long time but found the likely cause;

With longer duration exposures (i.e ambient rather than flash illuminated exposures), hot + dead pixel clusters will start to occur and (although Hasselblad's Phocus doesn't require it), a dark frame subtraction exposure is required for processing DNG made TIFF files.

The corrective process can be done by roughly following this (subtract) masking process outlined here:

https://monochrome.sutic.nu/2014/10/09/noise-removal-using-dark-frame-subtraction-and-median-blur.html

It has worked pretty well and once made into a custom optioned action I've found it to not be a major hassle (pardon pun)

The occurence of these hot pixels shouldn't be confused with artifact patterns which are more a result from DNG outputs from newer versions of Phocus (the older windows 2.8.3 vers does a decent job so far with H4D 200MS 6S .fff files).