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# Tag Info

## Hot answers tagged exposure-correction

5 votes
Accepted

### why exposing with 18% gray card does not give IRE near 40?

18% reflectivity means it should reflect 18% of whatever linear light is actually on it. Gamma should compute 117 at 46%, but your picture shows the card to be in some shadows, so then it can't be 18%...
• 12.9k
4 votes

### What is the formula to calculate aperture ("diaphragme" in French)?

The equation is: $${N^2\over t} = \frac{E \times S}{C}$$ for $N=$ f-number; $t=$exposure time (in seconds); $E=$ illuminance; $S=$ ISO value; and $C=$ incident-light meter calibration ...
• 143k
3 votes

### I Dropped my nikon D3300

It sounds like the mirror assembly is damaged, leading to incorrect light meter readings. In an SLR, the light metering sensor is contained in the viewfinder that gets its light via the mirror. The ...
• 538
3 votes

### Fixed camera and light settings return different exposure

If you're holding all exposure parameters constant, then the next suspect for me would be your white-balance setting, which I don't see mentioned above; e.g., do you have auto-white-balance (AWB) ...
• 211
2 votes

### Mathematical definition of EV on a RAW photo?

Your entire exercise seems to be built on somewhat of a false premise: That the initial image you see on your screen when opening a raw image file in ACR is a linear representation of the luminance ...
• 175k
2 votes
Accepted

### Where can I find color data for X-Rite ColorChecker Classic?

The reference data contains the CIELAB data for the following colour rendition charts: ColorChecker Classic before November 2014 ColorChecker Classic after November 2014 ColorChecker SG before ...
• 849
2 votes
Accepted

### Random EXIF data with same camera settings

I could finally verify that the problem was 100% caused by the lens. It was internally unstable and in certain position the internal connections were not communicating the right values to the camera ...
• 313
2 votes

### Random EXIF data with same camera settings

It looks like you've probably got 'Safety Shift' enabled and set to option 1: 'Shutter speed/Aperture' in your 70D's menu. It's found under the "Custom Functions" menu at 'Menu → Custom Functions (...
• 175k
2 votes

### Simple function to simulate different shutter speed / exposure by changing RGB values of image

The Kodak Gray Scale is the benchmark for your needs. Density is express as a logarithmic value. 0.30 density is a doubling of exposure = 1 f-stop a 2X change in opacity of film 0.60 = 2 f-stops 0.90 =...
• 39.3k
2 votes

### Simple function to simulate different shutter speed / exposure by changing RGB values of image

You can't really do that; at least not easily. As a general rule exposure in the (s)RGB color space is power 2.2; but first you have to normalize the number to a 0-1 base (i.e. 128 is .5 (% of 255max))...
• 17.7k
2 votes

### Can I save extremely washed out images in post-production?

Adjusting the exposure is a basic feature of the "developing" software. If you are shooting RAW images, you have more latitude in the image data than the normal presentation of such an image can ...
• 4,382
1 vote

### ISO blinking on Olympus omd10 ii how to correct exposure

It's telling you that it doesn't think the exposure is correct and it cannot adjust the ISO any farther. In aperture priority mode with auto ISO, as the light level drops the camera will reduce the ...
• 17.7k
1 vote

### How does the wireless flash protocol control exposure corrections?

The metering flashes are popped off one at a time before the shutter is activated for the exposure. The sequence is so rapid that it looks to our eyes like a singular pop, but it isn't. I don't know ...
• 175k
1 vote

### Fixed camera and light settings return different exposure

You mentioned there's an exif data incoherence with the parameters you shot. Although this could be an error of internal parts of the lens (dirt or moisture in the metal tracks of the barrel, whatever....
1 vote

### Fixed camera and light settings return different exposure

How repeatable is it? A few ideas: I've managed to significantly change light levels by standing between the light source and the subject :-) Are these always-on studio strobes or are they ...
1 vote
Accepted

### Post-processing goal: three different exposures?

While there are multiple ways to do this, my preferred approach is exposure blending. You basically take multiple exposures from LR and blend them together in Photoshop using luminosity masks. You may ...
• 715
1 vote

### What is the formula to calculate aperture ("diaphragme" in French)?

As you know, all optical filters absorb some light hence require an increased exposure to compensate. The magnitude of this increase is universally called the “filter factor”. This value is likely ...
• 39.3k
1 vote

### Exposure compensation after images are taken

Q: "How do I compensate the exposure of a bunch of photos so I can stitch them together?". I too disagree with the formula, shouldn't it be: $p' =$ \\$p + \left(p \times {k^2\over\tau\...
• 1,823
1 vote

### Exposure correction for a portion of an image

Yes, it is possible, especially if you also have a NEF file besides the JPEG - Adobe Camera RAW (inside Photoshop or Lightroom) allows you to bring down highlights without affecting the darker areas ...
• 2,055
1 vote

### Mathematical definition of EV on a RAW photo?

If I'm understanding what you are trying to do correctly, your starting point is fundamentally flawed. " ... takes in a matrix full of 12-bit RAW sensor values ..." OK so far. " ... and adjusts ...
• 2,239
1 vote

### How to programatically adjust exposure based on image metadata?

It depends on what programming language you have access to. It's easy to read exif data with MATLAB: https://blogs.mathworks.com/steve/2011/03/08/tips-for-reading-a-camera-raw-file-into-matlab/ but it ...
• 156

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