ProfHankD

ProfHankD

Lives in United States Lexington, United States
Works as a Professor
Has a website at http://aggregate.org/hankd/
Joined on Mar 27, 2008
About me:

Plan: to change the way people think about and use cameras by taking advantage of cameras as computing systems; engineering and creatively using camera systems to provide new abilities and improved quality.

Comments

Total: 1678, showing: 21 – 40
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On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

chriswy: Is it me? The "fixed" image blurred out a bit.

One more point: the "dust subtraction" done in many DSLRs is actually FAR WORSE than removing these stripes -- bad pixels blotted-out by dust are even larger spatially-highly-correlated blocks of pixels, and span all color channels.

Link | Posted on Apr 19, 2018 at 10:57 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

chriswy: Is it me? The "fixed" image blurred out a bit.

The dead pixel analogy is pretty accurate -- in fact, that's exactly how the rawtherapee repair done by pippo27 works. However, KARWY-SR is a tad different in that I have it deliberately add random noise to the repair so that the noise level in repaired pixels is approximately the same as that in similar pixels that were not affected.

It is true that the PDAF cells taken out by stripe artifacting are essentially spatially-correlated dead pixels, but they tend to be in low-detail areas (flare), the actual number of pixels affected is usually zero, and it is never a very big fraction of all pixels. It is not uncommon for a sensor to have thousands of bad pixels even without this striping; the worst I've seen is my fleet of Canon PowerShot SX530 HS (which I reprogram via CHDK), and they average tens of thousands of bad pixels in their 16MP sensors, but you'd never suspect that looking at JPEGs.

Link | Posted on Apr 19, 2018 at 10:30 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

Nick Brundle - Photography: When you buy a camera you want to buy the best available on your budget.
How can anyone in there right mind spend tons of money on a camera that creates "stripes" in the pics. A total mystery to me.

Dareshooter: "Imagine the furore if that was an issue on new Canon."

Huh? The 5D IV has a worse problem with how it handles its dual pixels -- it doesn't produce these stripe artifacts, but it degrades EVERY exposure. Zero bad press about that 5D IV problem.

I think Sony's class-leading sensors naturally attract more critical evaluation... and one of the staged scenes for the A7III press coverage just happened to be exceptionally unfortunate. Otherwise, I don't think this rarely-seen artifacting would have made much of a news splash either....

Link | Posted on Apr 19, 2018 at 01:04 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

Michael Ma: If you look at the "fixed" jpeg, you can see some lines still exist where the top of the forehead meets the hair.

KARWY-SR currently assumes it does NOT know where the PDAF cells are, which makes the problem harder (and blonde hair in the right orientation looks a lot like the artifact), but makes the tool work for all cameras having this type of artifact. However, the fix pippo27 implemented in rawtherapee does use the cell location information and thus might do better in this respect.

Link | Posted on Apr 18, 2018 at 18:24 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

pippo27: Just to clarify: there's no such thing as an "internal version" of RawTherapee. RT is an open source project, and everything is available to anyone. The fix was integrated in the development version a few weeks ago already.

And you deserve as much credit as I do for creating a fix. I would even go so far as to say that your approach is arguably closer to what Sony should do in-camera because yours makes excellent use of knowing where the PDAF cells are for the specific camera model.

Link | Posted on Apr 18, 2018 at 18:19 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

QuietOC: You should probably add the A6000 and A5100 to the list of cameras with this issue, since they seem to have the worst problem and vastly outnumber the A7 models.

I haven't tested an A5100. You're right that the A6000 has the light stripe artifact fairly badly and it is easier to provoke than some other Sony models. The A6500 is comparably easy to provoke, but the stripes are less obvious. KARWY-SR does fairly well repairing compressed ARW2 files from any of the models that get light stripes.

Link | Posted on Apr 18, 2018 at 18:14 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

chriswy: Is it me? The "fixed" image blurred out a bit.

It's technically not blur, but affected pixel values do get replaced by a value synthesized, including a noise model, from "similar" nearby pixels.

Link | Posted on Apr 18, 2018 at 18:09 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

durask: Well, if they say A7II does not have the problem then this is something that Sony can and should fix.

Also, I was on the fence whether to sell my A7II and buy A7III - now my decision is simple :)

Basically, all the Sony sensors I've tested that have PDAF cells on the main sensor have some version of this problem, but dark vs. light stripes, the severity of the artifact, and how easily the artifacts arise varies across models. The A7III seems to suffer light stripes that are more visible than most and can be provoked to happen more easily than the A7II's artifacting, although the artifacts are still not common under normal shooting conditions. The A7II suffers from dark stripes that are not as obvious as the stripes on the A7III, and it is harder to provoke the artifact; however, KARWY-SR was built to fix light stripes (fixing the dark ones will probably be added soon).

Link | Posted on Apr 18, 2018 at 17:51 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

Magnar W: A professor is posting a tool to help people if some of their pictures ever are affected by some rare stripes in small areas with strong flare, and look at the comments!

Brand warriors fighting, no one saying "Thank you very much, professor", and hardly no one saying: Good, then we have one more soultion for this issue.

So I will say: "Thank you very much, professor Hank, for your help, and for your generous and helpful attitude!

You are very welcome. I believe it's good for us engineering professors to do some actual, useful, engineering -- and all the better if it is in service to the community. :-)

Link | Posted on Apr 18, 2018 at 17:24 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

Relaxed: So is it a RAW, or a "RAW" :)

It's a compressed ARW2... which is Sony's raw format, but obviously not quite as "raw" as the original before repair.

Link | Posted on Apr 18, 2018 at 17:17 UTC
On article Sony 'striping': here's the fix (755 comments in total)
In reply to:

Vincent DP: Look at the hairs that cover her right eyelid... they are messed up by the workaround.
Anyway, better than no workaround at all.

Blonde hair strands in the right orientation look enough like the artifact to confuse the current version of KARWY-SR. When I bring KARWY-SR out of beta, it will probably be better at distinguishing. However, if we apply the current logic with additional knowledge of PDAF cell placement for that camera model, such errors become extremely unlikely -- that's what Sony should consider putting in camera.

Link | Posted on Apr 18, 2018 at 17:15 UTC

Large format digital will be a big thing... no pun intended. The catch is that these first sensors don't have the high resolution that will make it compelling for new uses, but the images on their site are indeed pretty compelling anyway -- pretty much for the reasons Rishi explained. Only thing here that's news to me is the price... which is high, but not insanely high.

Link | Posted on Apr 18, 2018 at 00:52 UTC as 77th comment
In reply to:

ProfHankD: Just to be clear, this appears to be a conventional DOF adapter, which basically means it is a camera obscura: the image is projected on a "film" plane and then that film plane is imaged by the cell phone lens. The "film" plane would be a material that acts as a focus plane, which essentially means a diffuser, such as ground glass or translucent plastic. The key problem is that the diffuser's texture will show, so most serious rigs incorporate a mechanism that physically moves/vibrates the diffuser so that any texture is smoothed; many use rotating ground glass, but vibrating would seem more likely here.

Without the motion of the diffuser, these are trivially home-made. Perhaps I'll throw-together a 3D-printed one just for laughs...?

Here's my old 3D-printed digital pinhole obscura: https://www.dpreview.com/forums/post/57666254

Looking at the video again, I doubt they're vibrating the diffuser....

Link | Posted on Apr 13, 2018 at 01:00 UTC

Just to be clear, this appears to be a conventional DOF adapter, which basically means it is a camera obscura: the image is projected on a "film" plane and then that film plane is imaged by the cell phone lens. The "film" plane would be a material that acts as a focus plane, which essentially means a diffuser, such as ground glass or translucent plastic. The key problem is that the diffuser's texture will show, so most serious rigs incorporate a mechanism that physically moves/vibrates the diffuser so that any texture is smoothed; many use rotating ground glass, but vibrating would seem more likely here.

Without the motion of the diffuser, these are trivially home-made. Perhaps I'll throw-together a 3D-printed one just for laughs...?

Here's my old 3D-printed digital pinhole obscura: https://www.dpreview.com/forums/post/57666254

Link | Posted on Apr 13, 2018 at 00:40 UTC as 4th comment | 2 replies

Basically, it sounds like Photokina just cut the benefit to exhibitors in half while effectively tripling exhibitor cost per unit time.

The cost of fielding an exhibit is pretty high: http://www.photokina.com/photokina/For-Exhibitors/Application/Calculate-stand-costs/index.php

Odd move for Photokina at a time when the industry seems troubled. Almost feels like a desperate attempt to draw more attention to the field...? If so, I hope that works.

Link | Posted on Apr 10, 2018 at 16:11 UTC as 32nd comment | 2 replies
In reply to:

A Owens: Dang, that tripod pixel shift looks good.

A Owens: Sony's NEX line did computational multi-shot processing to make-up for lack of IBIS, and Sony was pretty aggressive about it. It sure looks to me like they implemented sub-pixel alignment with quality-based region rejection and even warping to allow for lens distortion in movements of many pixels. They also didn't just use it for one thing, but for anti-shake, high-ISO noise reduction, 2D/3D panorama stitching, etc. Anyway, spatial SR and related algorithms were well known by the early 2000s -- they were just too computationally expensive for most cameras to implement, but it looks like Sony implemented them with hardware assist in the JPEG pipe (which would explain why no raw output).

Pentax seems to be using much simpler algorithms for PS. Artifacts include line and cross-hatch textures on some of the details, especially from the hand-held PS shots. For example, look at image #2 above the door where it says "IN SEMINE".

Link | Posted on Apr 10, 2018 at 00:54 UTC
In reply to:

A Owens: Dang, that tripod pixel shift looks good.

Actually, the PS shots all look a bit choppy. The straight shots look excellent. :-)

It's rather difficult to ensure pixel-level alignment because camera, lens, and scene components often move a bit -- as I found several years ago, even with a camera bolted to a concrete block, lens elements can shift within play of the barrel.

As far back as the NEX-5, Sony has been doing computational multi-shot alignment and enhancement (e.g., for anti-shake and noise reduction), and I don't think this is really doing any better and maybe not quite as well. The catch is that Sony's processing only produces a JPEG result: no raws.

Link | Posted on Apr 9, 2018 at 23:26 UTC
In reply to:

ProfHankD: "By then [before 2020], it would make sense for both Canon and Nikon to have replicated their most important tele primes and wide-aperture zoom lenses in their respective new native mirrorless mounts"

That's highly unlikely. Releasing adapters to whatever new mount (like Sony) is much more likely, but Sony is now years ahead ON NEW FF MIRRORLESS LENSES. Pentax tried the other way forward -- mirrorless using the SLR mount -- and it wasn't a resounding success. Canon's EF-M mount could be used for a FF mirrorless, so they're actually a step ahead of Nikon if they decide to go that route. Fuji's "oversized FF" actually seems a smarter upgrade path.

The MFT makers have a bigger problem: the 4:3 aspect choice was wrong, the guess that bigger sensors would be prohibitively expensive was wrong, and they're stuck with that choice. They even have a relatively long flange distance....

cdembrey: Nice try, but the logic behind FourThirds was primarily CRTs for PCs and TVs, and MFT inherited that already-outdated decision. Aspect ratio cropping wouldn't matter so much if MFT used a bigger sensor, but cropping 4:3 to match the now-dominant 16:9 standard, or even 3:2, really hurts. Resolution expectations have risen beyond what's easy for lenses to deliver on an MFT sensor; new MFT lenses often meet the challenge, but many older lenses don't.

The big problem for MFT is that the entire FourThirds system was designed with very little wiggle room for upgrading. Sony's E mount just barely allowed for FF use, but you can bet that's not a coincidence; Canon's EF-M leaves even more margin for FF. MFT is basically stuck without an easy upgrade path. You can argue it's good enough, and in many ways it is, but it's going to get harder and harder for MFT to be compelling against cell phones; I think MFT's future is in space/weight constrained drones, etc.

Link | Posted on Apr 9, 2018 at 02:35 UTC

"By then [before 2020], it would make sense for both Canon and Nikon to have replicated their most important tele primes and wide-aperture zoom lenses in their respective new native mirrorless mounts"

That's highly unlikely. Releasing adapters to whatever new mount (like Sony) is much more likely, but Sony is now years ahead ON NEW FF MIRRORLESS LENSES. Pentax tried the other way forward -- mirrorless using the SLR mount -- and it wasn't a resounding success. Canon's EF-M mount could be used for a FF mirrorless, so they're actually a step ahead of Nikon if they decide to go that route. Fuji's "oversized FF" actually seems a smarter upgrade path.

The MFT makers have a bigger problem: the 4:3 aspect choice was wrong, the guess that bigger sensors would be prohibitively expensive was wrong, and they're stuck with that choice. They even have a relatively long flange distance....

Link | Posted on Apr 9, 2018 at 01:15 UTC as 184th comment | 6 replies
In reply to:

ProfHankD: Are they really selling a semi-fisheye for $700?
Good converter optics (e.g., Raynox) for that cost well under $100.

Trebor1: What? Yeah, the base has 3 elements... I don't see anything exciting about that. Basically, this cuts the production cost by sharing the last few elements, focus, and aperture, and it does make the front parts of the lens smaller. However, they don't seem to be passing-on the cost savings, the size advantage only happens if you get multiple front lenses, flare seems pretty bad, and even the rather favorable review you cited basically has this not very sharp on 16MP FF (which suggests it would struggle to produce sharp 6MP APS-C).

I fully understand that paying several times the price to get a smaller, funkier, optic appeals to some hipsters, but I see very little to recommend this.

Link | Posted on Apr 7, 2018 at 02:08 UTC
Total: 1678, showing: 21 – 40
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