Defocus Puns

Hello guys, I am interested in computational photography using a camera with ML. I was looking for the definition and some papers about defocus blur kernel and PSF with RGB camera. Some of the people say that defocus blur kernel can be regarded as gaussian and others' result seems to imply that it's constant.

My first question is... Is it okay to regard the defocus blur kernel as gaussian kernel? If it is, I want to know the reason why. For me, it is more reasonable to say that all the ray from single point contributes to the blur kernel equally.

Finally, I am also a little bit confused about the definition of defocused blur kernel and PSF. What's the relationship between them?

I couldn't find any resource and paper that clearly answers these questions. If you can introduce some papers and good lectures about these questions, I will appreciate that.

Sorry for a lot of questions... I really need help. THANK YOU FOR LISTENING.

So the plate has a defocus that starts at 1001 and slowly goes to focus by 1100.

So I'm using a Zdecocus node, obviously that's blurring the grain a bit. Is this what happens behind a camera? Or does the grain stay the same no matter the focus? I'm assuming I have to add the grain back over the defocused area?

Thanks!

The hyperopic defocus theory of myopia states that when wearing normal corrective lenses that bend light perfectly on the center of the retina, but past the retina in the peripheral regions, this causes axial elongation to reach emmetropization. Ortho-k myopia control therapy is based around this theory. Ortho-k slows down myopia progression by flattening the cornea as to prevent hyperopic defocus, so light is focused evenly on all areas of the retina rather than just centrally. Theoretically, would this also apply to refractive surgery as well, since refractive surgery ultimately carves the cornea as to bend light further into the elongated eye onto the retina. I can find only one study regarding peripheral retinal focusing after lasik, and it’s inconclusive, based on theory.

If this theory is correct, refractive surgery is also a possible although controversial method to slow myopia progression. This would explain the rarity of myopic progression (or regression) after refractive surgery regardless of near work

I absolutely feel that my eyes are 'doing something' when I do it, but they don't seem to move. What exactly goes on inside the eyes that we can simply make our sight blurry or out of focus at will?

What is the best location to find data to recreate defocus curves for IOLs?

Edit: Student

Recently I met my old friend from high-school who now works as psychiatrist. We had talk about misophonia, OCD, mental-illnesses, etc. He suggested me to try method of holding breath as a way to stop onset of misophic rage as it should defocus brain from trigger. I am trying it being surprised how good this simple, yet effective method actually is. It seems to be ideal when exposed to isolated triggers mostly, triggers that are not repeated from many sources too often, as of course it is impossible to hold breath too often repeately in a lot of social situations. Anyway, normally, without this holding breath method, when I hear trigger, my misophonic chain builds like this: trigger completely takes all of my focus, trigger starts to repeat in my head involuntary against my will, while my brain anxiously waits with all its attention on when that trigger will be heard again and during this time my misophonic rage builds in my head being strongly multiplied and multiplied when trigger is heard again and again. But when I hold my breath to point I cannot stand holding my breath anymore, it erases this whole misophonic chain completely. It is like brain being reset to misophonic state 0, state before that trigger was even heard, before misophonic chain started to build up. It simply seems my brain cannot focus on triggers and building of misophonic rage while it has life preserving problems. :)

Hi, I'm trying to render a video and everything is normal (VEGAS uses ~80-90% of the CPU) until it starts rendering frames with defocus and uses only 4 out of 24 threads. It takes few seconds per frame when it does so. Is it normal behaviour?

1. Vegas Pro 15 Edit
2. Ryzen 3900X
3. Windows 10 1909
4. Nope
5. No
6. Yes

Uniform bokeh is easily the biggest giveaway if a shot is comped.

edit: I'm not saying shots look fake without it, but whenever I want to tell if a shot is BG replacement or practical BG (led wall, translite, etc.) this is a very easy way to tell.

> Can wearing the wrong prescription make my eyesight change? Hi, My glasses are two years old and since then my eyesight has changed. My glasses prescription (2 years old) is -3.25 (RHS) and -3.00 (LHS). My contact lense prescription (recent prescription) is now -3.50 and -3.50. So my eyesight was worse in my right eye two years ago but at my last appointment for contacts my eyesight in both eyes was equal. I usually wear my contact lenses for 6 days a week but the last couple of months have been wearing my glasses nearly everyday and my contact lenses maybe only 1 day a week. Today I noticed that without any glasses or contact lenses, my vision in my left eye is blurrier than my right eye.

> However, wearing my contact lenses my vision is in my right eye is blurrier. Do you think wearing glasses with an unequal prescription has made my eyesight change so now my prescription would be different in both eyes? If that is the case, why is the left eye the more blurrier one without any lenses/glasses and the right the blurrier one with contacts? Should I keep wearing my glasses knowing they are uneven or wear my contacts to try and even them out again Obviously given the circumstances I cannot go to the opticians right now. I should add that the differences are subtle and I only noticed it incidentally when I was rubbing one eye and my vision was blurred.

Reposted from Optometry

> So it’s is still unclear if seeing something at 25cm with full corrections (or emmetropic eye) results in hyperopic defocus. Or even 30cm or 65 cm (usual screen distances). If near work does result in hyperopic defocus, then it certainly can account for the axial elongation.

It doesn’t if you think centrally. Because centrally you would see blur. Otherwise there is no defocus. Defocus = blur. And no one sits reading a book in blur, at least usually not normal people. Because even small amount of blur while reading would mess up your reading. So there is no defocus centrally from close-up. Only peripheral. If you read a book you are not interested if your peripheral words at top of the book are in hyperopic blur. You’re reading words centrally.

That’s why glasses are sold to begin with. Because you as a reader are not interested in correct defocus in your periphery. You’re interested in reading the book centrally.

You would now ask: Ok captain obvious, so why don’t they cause the same 1v1 blur in periphery to prevent that from happening. And the answer is: they can’t do that without messing your central vision.

They could tell you: use undercorrected glasses for close-up but then they’re opening can of worms. Why do you need that? Because glasses worsen your vision. Glasses are bad. People start improving their vision all over the world. Sueing optometrist for destroying their vision. And lens business in turmoil. Optometrists starting making Jake’s youtube vidoes about natural improvement. Lasik guys go to prision. Contacts producents lose their jobs. There are hundreds of thousands of people in this and who on the opposite side? You and me with our efforts to improve our vision. There aren’t many such people. And one bearded guy doing some stuff in some remote place in Asia. To believe in this you need to question mainstream beliefs and most people don’t do that.

Is this some conspiracy theory? No. 99.9% of those people in this business don’t even know or think about this. They got the info in their educational process: Vision is bad from genetics. You can’t improve it. End of story. They will not question mainstream belliefs, and they don’t do their own studies. Even if couple of guys researching this have some suspicions nobody has any monetary incentive to change this stuff. And in the end improving is about habits so you can’t prove that it will work for everybody. So you can’t really prove or disprove EM. And in 100 years some other bearded

Hi all,

I used defocus node for a BG, however it creates a vignette around the BG plate. Is there a way to prevent this?

https://bjo.bmj.com/content/early/2019/05/29/bjophthalmol-2018-313739.abstract

I’ve been able to make everything around me blurry whenever I want. On command. Is it rare?

Hi, I have a full CG shot of a city street with a bright light in the distance.

I want to do a depth of field thing using ZDefocus+Zdepth, everything looks fine except all the bright light source/hot spots sort of dimmed out. Basically I was expecting a bright bokeh-ish effect but i ended up with an ugly looking color splotches.

here's the screenshot.

https://preview.redd.it/p8anxe7w79i31.jpg?width=753&format=pjpg&auto=webp&s=b6cfb3b7e59010ca183896ecc031c665f84ba4c2

is there any way to get around this? thank you!

Can someone explain what is the difference between those two lenses? I’m not I understand what the Defocus Smoothing brings.

Hi, I'm 18M. I have this problem going on for almost 2 months. When I'm looking at my computerscreen or sometimes at other things. My eyes suddenly get the urge to defocus, to a point where i can't hold it together anymore and they end up defocusing and vision gets a bit blurry. This happens for a really short time, for like 3 seconds. After this i can focus again. Also I'm having trouble reading for longer times, and am sensitive to light to the point where i get a headache.

EDIT: The headache is on my forehead, close to my eyebrows