Adjusting Levels with a Histogram
Let's say this is a scanned photograph. You have an old photo of you. You put it on a flatbed scanner, hit the scan button, and here it is in photo shop. Well, if I come in here and choose levels, you should be aware of the bar chart that's in there. That bar chart is called a hist. A gram in all history Graham does is it tells you which brightness levels are found in your picture, in which ones are not. So. If I zoom up on this, if you compare that bar chart to the bar that's down below, that has those brightness levels in it. If you were to pick any shade from that bar and goes straight up until you hit the bar chart, if there's a bar on the bar chart than that shade is found somewhere within your picture. If on the other hand, you choose a shade, you go straight up and there's nothing in the bar chart at all. Then that is not found in your picture. It's not even a single speck of it is in your picture. So what that tells me with this particular hissed a gram is it's empty over here ...
on the left side, and that means the darker shade in the entire picture is right here. And if I go straight down from it, it's exactly that bright. Well, doesn't this slider here for serious to black? And if I pull it over, let's say, just by chance to right there, wouldn't that force the shade that has found directly below two black? That's what it does. And if that happened to be the darkest shade in our photo now the darker shade is black on the opposite side of the history. Graham, you notice a gap over here, which indicates the shades down here are nowhere to be found in the image. There's nothing near white in this photograph, but if I pull this slider in until it touches the history Graham, then that's gonna force whatever is directly below this toe white. And now the brightest area of her picture is white, and therefore, if I were to click OK and open levels again, I'd see an updated, hissed a gram and updated. One would span the entire width because they forced the darkest area to black in the bread hysteria. White zoom out. Look at her picture. There's a preview check box here. If I turn it off, you'll see before turn it back on and you'll see after then. After doing that, If the image is a little too dark or too bright, I could grab the middle slider and brighten it up or darken it up. Then, if I have that printer I described earlier where I'm printing on really cheap paper using ink, and I find that the darkest part of the image I lose the detail and the lightest I could get, I should say the darkest I can get where I can still see detail. Let's just say it was 90% brightness. Well, I could pull this in until it points at 90% and therefore the darkest part of my picture is not gonna be black. It's gonna be what this points at, and you can use the numbers that are in here to figure out exactly what setting you're using its fans from zero, which means no light whatsoever 2 to 55 which is a much light as you can possibly get. And that's because a normal image has 256 brightness levels, and if you count, zero is a number. That's 256. So you could figure out if this is 100% of the light to 55 then what would be 1% of this number? Well, 10% of it will lead 25.51% would be 2. So if you want to convert, you can take whatever percentage you want and multiply it by 2.55 to figure out what it would be in this numbering system.