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Messages - Guillermo Luijk

#1
Could you please show 100% crops of the shadows and the highlights in exactly the same area for dual and std ISO?.

At web picture sizes dual iso will always produce cleaner images, while 100% crops are more representative of what you would achieve printing large.

Regards
#2
Would it be possible according to the way Liveview works, to have information in the RAW histogram not only about clipping taking place, but about how many stops of highlight info are currently getting clipped? i.e. an estimation of the histogram of clipped RAW data.

E.g. the orange bars represent info that would get lost if we click:



With Liveview capture working 2 stops below user settings (either with lower capture ISO or exposure), ML could plot a RAW histogram including those 2 (or any other number) extra stops of clipped RAW data with present user settings. This could visually and intuitively help in achieving accurate ETTR in M mode.

I actually prefer zebras over the histogram, but this would provide an enhanced histogram anyway.

Regards
#3
Quote from: josepvm on October 29, 2015, 08:13:00 PM
Gullermo, as far as I know, it is not possible to set different ISO values to arbitrary areas of the sensor in a single shot. Only two values for alternate rows. And that's because Canon hardware is designed that way.

OK this is the key. I thought the sensor readout gain could be individually set for every row of photosites. Not being this possible my approach is nonsense.

Regards!
#4
You mean me? I don't even have a Canon body with ML sorry. Anyway the loss of resolution in dual-ISO is a fact because of the strong interpolation needed, right?. The opposite would just be miraculous.

Regards
#5
Dual ISO needs interpolation in the deep shadows and in the highlights which can end in loss of resolution and artifacts.

This method would only be valid in certain scenes (like the ones where a GND filter is), but requires no extra interpolation, just the standard Bayer RGGB, so you have both the full resolution of a standard capture and the DR of dual-ISO.

Regards
#6
Why is it not possible if dual-ISO, much more complex, is possible?
#7
There would be no bands. All the areas are to be corrected to match the ISO100 exposure before saving the final RAW file like dual-ISO does with the high ISO values.

I.e.
RAW values from ISO200 must be divided by 2
RAW values from ISO400 must be divided by 4
...

This is not a GND filter emulation, it's a way to obtain an enhanced DR linear RAW file by increasing SNR with ISO. I just mentioned GND filters because of the division of the scene in different luminance horizontal layers.

Regards
#8
Following the same DR enhancement principle as used in dual-ISO, different ISO values could be user-defined for different horizontal areas of the sensor according to the scene, in a similar way GND filters do but far more configurable:




The DR enhancement can be up to 3 stops but interpolation is not needed in this case, so the loss of quality and issues found in dual-iso captures cannot take place.

The captured RAW data needs to be previously processed reducing RAW levels on the ISOs above ISO100 in order to have a final RAW file with uniform RAW levels (the same as those found in the lowest used ISO).

Sorry if this idea has already been posted or some technical reason makes it impossible to implement.


Regards
#9
Bits in the RAW file are necessary for a certain DR, but they are not enough. DR is limited by noise rather than by bits.

For instance the Canon 40D produces 14-bit RAW files with two totally useless bits. If you truncate to 12 bits its RAW files (by zeroing the two LSB's) and then develop them there is no quality nor information loss vs a 14-bit RAW development.

My Olympus E-P5 with 12-bit RAW files has more DR than many 14-bit Canons like the 40D, because its sensor has lower noise despite the also lower bitcount.
#10
I don't know how to quote someone's post on this forum so I copy&paste here a comment by alexpok:

"I found some problems as well, i will try to describe them below, may be it helps to improve this wonderfull tool.

1. I decided to limit testing  by only 2 shots, 3EV difference. The reason - the quality already very good in case of no problems, in case of some problems additional files only makes it worse.

2. I made 2 sequences by 2 shots, run CeroNoice, run DNG_validate as described. The only difference between these sequences was one additional lamp turned on - it produces some highlights on scene. In good case (lamp off) i just process out.dng in Adobe Photoshop camera RAW 8.3 - i did not ..."



You will never get good results with the ZN algorithm if your images are not linearly correlated in exposure. If you switch on a lamp, not all pixels of the scene get the same extra amount of exposure, so the ZN algorithm will produce terrible artifacts in the merged composite. You would need a very wide progressive blending parameter (no idea if alex's ceronoice implements it) and even in that case the results can be wrong.

For such type of differently exposed images, I have found the Enfuse algorithm (actually I always use the Tufuse implementation by Max Lyons) very robust. It is capable of even merging quite finely 2 shots where a flash was used only on one of the captures.

Regards

#11
I think you are asking too much from a pixel selection algorithm, it will never work properly on moving scenes. What I do with ZN (the genuine one!) when moving parts of the scene affect differently lit areas, is to manually edit the blending map, forcing all pixels are taken from the same RAW source file. That would have worked perfect on the sea waves.

Automated anti-ghosting:




Manual anti-ghosting:



Regards
#12
Feature Requests / Re: Advanced Bracket Features Request
December 16, 2013, 10:40:18 PM
Hi all, my name is Guillermo Luijk, the author of Zero Noise. If any of the underlying ideas or algorithms in ZN can be of help to improve ML, I am ready to give ideas.

I have to say I don't know the details of the dual ISO mode in ML (it works on alternate lines? it works on RAW or demosaiced data?), although I understand the basics about it.

Regards