diopter – How do I chose the right “correction eyepiece” when I need to go past the furthest left on a Nikon viewfinder?

This prescription is for -1.25 diopters (under “sphere”), plus some astigmatism (“cylinder” and “axis”). You won’t find an off-the-shelf corrective piece to deal with astigmatism — usually we just ignore that.

The add-on corrective eyepiece is designed so the nominal number is the result when used in combination with the existing adjustment in its neutral position, which will be -1 (not 0). So, the -2 diopter seems right; you can then set the adjustment in the built-in diopter a couple of clicks to the positive, so your end result is around your prescription of -1.25.

On rereading several times, I see the source of your confusion.
The prescription tells you the correction you need. You’re thinking that maybe it tells you the error of your eyes and you need the opposite to counteract that — nope. Just get a corrective lens that matches what’s written.

nikon – Why does high brightness affect white balance correction?

Your greycard is not filling the frame. That won’t help at all. Fill the entire frame with it. Focus is not important.

Right now, you have a huge area of ‘not grey’ for the system to contend with.

The whole idea of the white balance preset is that you present it with a known quantity – an 18% grey field, completely filling the frame, in the lighting you intend to use it.
If the lighting is far too bright, even when you’ve narrowed your aperture right down & dropped ISO to 100, then you will need a darker greycard, maybe a 50% grey.
You don’t need correct exposure for ‘a photograph’ when you do this, you need correct exposure for your greycard.

Setting WB needs a grey field, not absolute white. Absolute white is the maximum your camera can record. RGB values of 255, 255, 255. Once you hit that, you are out of gamut. Anything brighter is still all 255s, even if the colour in real life was dark green. If you over-expose it massively, all the camera will be able to record is all 255s… perfect white. There is no balance left to be set with this as input. The camera needs lower input numbers to be able to distinguish how far away from ‘flat’ the colour is.

“White” balance is actually a misnomer in this respect. Instead, think of it as “light grey” balance.

Your photo, btw, looks pretty flat to me, especially in the centre of the greycard. I am puzzled at what you managed to do to it to make it flare out like your top picture… & what you used to do it. Setting WB from it in Photoshop produces no discernible change.

From comments, it appears that the top image was taken after using the bottom image as a white balance measure.
What wasn’t taken into account, therefore, was simply… exposure. It is just massively over-exposed. No amount of white balance will fix that; it’s all pretty much solid 255s with a pale pink border.

I think the ultimate lesson to be learned here is that white balance is not an exposure meter & cannot be used as one. You expose for the greycard specifically. Your actual photographs must be exposed for the actual scene lighting, which will be different.

You can use the exposure meter in the camera to set the optimum lighting for your WB capture. A few seconds after you hit Measure, then Overwrite, your viewfinder goes back to ‘normal’ & you set your exposure to the greycard, the same as for any regular photo [the camera is always in full manual at this point, whatever it was set to outside this mode. Focus is not required [or checked] at all in this mode, as you often have a greycard too small to fill the frame and remain in focus]
Fill the frame with your greycard [fill more than the frame, your viewfinder only shows 90% of the resultant image, so go closer], tweak exposure time, aperture &/or ISO until you hit dead centre on your in-viewfinder metering.
This will set WB to PRE in your regular on-screen display & you go back to setting exposure/focus for your actual photos, as normal.

Can the Nikon D5200 shoot video with white balance correction?

I have a Nikon D5200 and want to use it to shoot video with white balance correction. I am able to shoot photos having saved the a test photo as a white balance preset (page 79 of the reference manual), and I am able to shoot video (switching to live view and clicking on the red button, from page 101 of the reference manual). I am unable to do both and shoot video with the white balance preset from the photo. Page 221 lists all the modes and those that have white balance available, and video does not seem to be one of the modes. On page 245, setting #2 uses white balance and the battery life of shooting movies uses setting #3, which does not use white balance.

Can the Nikon D5200 record movies with white balance correction at time of recording?

How to submit a correction to Timatic?

If I believe that I’ve found an error in Timatic—for example, it claims that a particular document is not required, but I believe that the document is required under applicable laws and regulations—is there any way to ask them to consider making a correction?

olympus – How does camera firmware obtain lens distortion correction parameters?

I use an Olympus MFT system and one thing I notice is that for most Zuiko MFT lenses there is significant barrel distortion as seen in the raw images. However, if you look at the jpg’s, often they have little or no distortion, so apparently it is getting corrected automatically by the camera firmware.

Does the camera (1) just guess at the distortion pattern and apply the same one to every jpg, or (2) does it have some way to detect the lens and have individual distortion correction patterns for particular lenses that it knows about, or (3) does it have some way to detect the distortion by analyzing the image itself and correcting it by image analysis?

Advice for good DVD Reader with excellent error correction?

We have to archiv some DVDs and could not read these discs with our standard DVD altough they are not scratched. They are pressed ones, so we are fear of already lost them.

Which actual DVD Reader you use for bad discs?

white balance – For a given lens/camera, will a ND filter always need same WB correction in all conditions?

I’ve taken a few photos with a new B+W ND 6-stop filter and found that it leaves them quite warm. I’m able to correct this in ACR using temperature/tint sliders. For the few photos I’ve taken so far, the same temp/tint settings seem to work for each one.

I’ve heard that color cast from a given ND filter can vary between cameras and lenses. But presuming I continue to use this filter with the same camera and lens, is it safe to assume my WB correction will be the same every time, for any photo? Or will it be dependent on other conditions like lighting and exposure/aperture?

Note that I ask, because if the color cast varies based on some conditions, then I will probably take no-filter companion shots for any filter shots that are important, so I’ll have a reference point for matching WB later. Though, it would be nice to not have to always do this.

Why double error correction and quadruple error detection cannot occur at the same time?

enter image description here

What does ( we cannot both correct double errors and detect quadruple errors because this would require us to interpret a received codeword in two different ways) means? I understand how double error correction works but I cannot imagine quadruple error detection. Can anybody show me example why double error correction and quadruple error detection cannot occur at the same time because it requires different interpretation?

For example, if double error correction occur,

will be something like this. How about quadruple error detection?

special functions – Correction of HeavisideTheta in MM11.3 to generate the same results with UnitStep in MM5.2

the UnitStep has been replaced by the HeavisideTheta after version 6.0 (reference here), but some differences confused me between the old and the new version as follows (For convenience, the f (x) is simplified). I want to know how to correct the HeavisideTheta in Mathematica V11.3 to generate the same results with UnitStep in MM5.2. For the problem, I have proposed a few methods (here and here), but which have not given the result I want. Thank you.

Code in V11.3

f(x_) := 1;
Integrate(f(x)*HeavisideTheta(x), {x, 0, (Infinity)})
Integrate(f(x)*HeavisideTheta(x), {x, -(Infinity), (Infinity)})
Integrate(f(x)*D(HeavisideTheta(x), x), {x, 0, (Infinity)})
 f(x)*D(HeavisideTheta(x), x), {x, -(Infinity), (Infinity)})

Code in V5.2


Results in V11.3

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The results in V5.2

enter description of image here

automata – Correction of an error in CFG

Here is a CFG that generates the language of basic arithmetic expressions. These expressions allow the 4 basic operations on the arithmetic values ​​a, b and c. It implements an order of operations where multiplication and division take precedence over addition and subtraction, and all operations are associative on the left. It also implements parentheses. There is an error in this CFG.

S → S * T | S / T | T
T → T + V | T-V | V
V → (S) | a | b | vs

You must rewrite this CFG to accomplish as many of the following tasks as possible:
a) Correct the error in this CFG to make it work as described.
b) Add an exponent operation. This operation must have a higher priority than multiplication and division, but a lower priority than parentheses. The exponent operator is ^. For example, a ^ b would be ab, or "a to b". Give this operation, and only this operation, associativity on the right, so that a ^ b ^ c would be "a au (b to c)".
c) Transform these expressions into equations. An equation consists of an equality operator {=,<,>} with an expression on each side. The equality operator must have the lowest priority and the equality operator must not be allowed in parentheses.