Here is an alternative/additional take on this. I will use ANAYV's weir image to illustrate.a extra edit:
exposure adjustment EV -3 or +3 is NOT the same as gamma and blacklevel.
Gamma max out right something in the range of +1/2 ev.
gamma max up, notice the tone curve.
1/2 ev up histogram looks almost the same, but the tone curve is less up and see the trunk ofthe bird
So gamma up for brightness correction is ripping out the contrast of your picture even when the overal image is looking nearly the same.
go the other way, gamma max down and blacklevel max up, heavy contrast lower section.
ev -3, overal contrast is the same (tone curve stays the same.) even -3 can reach the overal darknes of the image with gamma and blacklevel.
Some more testing reveals the nature of the line:
hit auto adjust ev and it gives +.65, line and tonecurve stays the same.
use the hystogram as comparing tool to try to get the same image.
try to get the same preview by brighten up more.
my conclusion:
EV: is raising or lowering the straight line in the tone curve tool/histogram without changing angle of the line, contrast (tone) or Dynamic Range and when image reach clipping point you see the spike on the right appear , highlight is falling out the dynamic range , clipping colors.
shifting the tone curve range , steepen the line, is the opposite of HDR. or dodge-ing/burning.
So imho the tone curve tool shows me the difference of the sliders/tools even when the image looks almost the same using different tools (ev).
step one: histogram and EV adjustment top get the spikes/blobs in the middle (crop first if needed)
step two: use dodge and burn tool to level out to the clipping points left and right.
Step three: White Balance setting for overall color temperature.
step four, use tonal tools like contrast(center), saturation, black level, gamma to spike (no correlation :-D ) up the image more.
step five: sharpening.
Eye drops do some combination things automatic : skin color enhancement, black level tool, grey balance. these are like the auto exposure button, sometimes nice other time ugly.
edit: the tone curve tool is just more agressive than the sliders , they give adjust room around the base tone curve. But you can totally twist the image around to a "alien" image with the tone curve tool. But for normal post processing a image it is more a measurementdevice to see what is happening in the image and not a tool. (or you must go over the restriction of the sliders......)
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LOL !!! No.I have several buckets of different height, so analogy is with DSLR Prime lenses, not with zoom lenses.
yes this is a overal (every color/tone is effected) kind of exposure adjustment. Like the line from 0 -255 is the color/tone range and this go's up and down as a hole pushing tonal points over the edge (clipping)Here is an alternative/additional take on this. I will use ANAYV's weir image to illustrate.
NOTE that in all the following we are looking at the Luminance tone curve.
#1 - Here is the image as loaded (default values for all parameters).
#2 - Here it is with over and under exposure warnings turned on.
#3 -Here it is with Exposure bias set to minimum. Everything is darker. From the brightest to the darkest areas of the image, everything is darker.
i was chewing on the things i posted before is fell a sleep, and the black level and gamma are effecting there own two sides of the tone curve. Black level effect the darker area's more then the brighter eara's. (the lower half of the curve so above the neutral point crossover point in the straight line) and the gamma is effecting the more vibrant brighter tonal section, (the upper curve) They have some overlap and that effects the contrast center.
#4 - Here it is with Exposure bias set to maximum. Everything is lighter (except the areas which were clipping to start with and so can't get any brighter).
#5 - Here it is with the Black level set to maximum. Compare this with #2. The bright areas are still bright. They may have got slightly darker, maybe not, but not much anyway. The dark areas have got a lot darker. The Black level slider only moves to the right, and moving it to the right concentrates its darkening effect on the dark areas.
Yes but Exposure Bias also effects the dark tonal( lower section) equaly and Gamma not so i couldn't get the same image : the dark pixels stay dark with Gamma.
#6 - Here it is with the Gamma set to minimum. The effect is somewhat similar to increasing the Black level, but the dark areas are not as dark as with the Black level set to maximum.
#7 - The Gamma slider moves in both directions. Here is the image with the Gamma set to maximum. It is somewhat similar to turning the Exposure bias up.
Yes that was what i mend, the sliders are much more subtle and give a lot less change/mm movement. The tone curve does big changes with small movements, a lot more difficult to control. Ive you make the tool window as big as possible the precision is a lot better and after using the sliders you can use the tone curve tool to get further and adjust over the limitation of the slider. (maybe it work also other way around: first tone curve adjustment and fine tuning with the sliders...)
Going off now in a different direction, I think the Tone curve is more than a measurement tool. I think it can be used to make useful changes to the image, changes that it may not be possible to make in other ways.
I think that's one of the main pro's of the tool, by pinning the correct tone section of the tone curve you can change a specific part of the curve without effecting the other parts.Here is an example
#8 - Here is the images with HDR set to maximum. This makes the image usable.
However, the water cascading over the weir looks a bit flat to me. I would like to brighten it up. However, I have already used the HDR slider so I can't use that. I want to affect just the bright areas. This animation flips between #8 (with HDR applied to max) and the same version, but with a very slight tweak at the top end of the histogram. The brightest areas of the falling water are a little more lively now. (The brightest areas are now clipping more, but that is beside the point for this illustration, the point being that you can have an effect on selected area(s) of the tone curve. But like I've said previously, I have found it difficult to use - easy to get wrong and make the image look bad. And given what I can achieve with the sliders in SP7 I haven't felt the need to use the tone curve - and the same in Lightroom incidentally.)
(There are three points on the diagonal line beneath the one at the top which is above the line. Those three points are there to "pin" the curve to the line, so the only change is right around that top point. If you don't do this pinning the curve gets altered all the way down.)
it is very interesting this section of adjustment. in need to do more testing/ learning/exploring before i can control and fully use this.Click on Original size to see the animation flip between versions.
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Nick
http://www.flickr.com/photos/gardenersassistant/collections/
GardenersAssistant Photography Videos - https://www.youtube.com/channel/UCmBgEwRDfiQMYTPORSzDxvw
https://www.talkphotography.co.uk/t...-dslr-primes-a-journey-of-exploration.531050/
I did a second look at it and i think there is a mixup between tone curve and luminance wave/histogram. A histogram represents the amount of light it radiates (how many red, green and blue and how many overal light is emitting (luminance)
waved line is tone curve, grey filled wave is the histogram of luminance.Here is an alternative/additional take on this. I will use ANAYV's weir image to illustrate.
NOTE that in all the following we are looking at the Luminance tone curve.
#1 - Here is the image as loaded (default values for all parameters).
#2 - Here it is with over and under exposure warnings turned on.
#3 -Here it is with Exposure bias set to minimum. Everything is darker. From the brightest to the darkest areas of the image, everything is darker.
above: only wave luminance is changed , tone curve remains the same. so the build up of max black to max white remains the same.
#4 - Here it is with Exposure bias set to maximum. Everything is lighter (except the areas which were clipping to start with and so can't get any brighter).
apparently there isn't much blacklevel material so the tone curve didn't change much. only the luminance wave changed alot.
#5 - Here it is with the Black level set to maximum. Compare this with #2. The bright areas are still bright. They may have got slightly darker, maybe not, but not much anyway. The dark areas have got a lot darker. The Black level slider only moves to the right, and moving it to the right concentrates its darkening effect on the dark areas.
But in the tone curve there is a lot of difference, the point where the wave is going under center point is a lot faster.(more to the right.) so most of the bright parts are changed to mid/dark tone
#6 - Here it is with the Gamma set to minimum. The effect is somewhat similar to increasing the Black level, but the dark areas are not as dark as with the Black level set to maximum.
The hole tone curve is lifted upwards, dark section is totaly gone, everything is bright or high mid tone. (luminance shows no black tone at all.)
#7 - The Gamma slider moves in both directions. Here is the image with the Gamma set to maximum. It is somewhat similar to turning the Exposure bias up.
It looks to me that the tone curve stays nearly the same and luminance is changed in the black and bright section (looks like two images gamma low and gamma max are stiched together no black level touched.
Going off now in a different direction, I think the Tone curve is more than a measurement tool. I think it can be used to make useful changes to the image, changes that it may not be possible to make in other ways. Here is an example
#8 - Here is the images with HDR set to maximum. This makes the image usable.
So it looks to me that blacklevel influence the lower halve of the tone curve and Gamma (because its is to go two ways from basepoint) can influence the hole tone curve. And the tone curve represents the amounts of all the different tones of the pixels, the most black pixel al the way up to the most bright(white) pixel. And luminance is the "backlight" of the image, how much light is go through the fabric of the lamp cover so to speak.
However, the water cascading over the weir looks a bit flat to me. I would like to brighten it up. However, I have already used the HDR slider so I can't use that. I want to affect just the bright areas. This animation flips between #8 (with HDR applied to max) and the same version, but with a very slight tweak at the top end of the histogram. The brightest areas of the falling water are a little more lively now. (The brightest areas are now clipping more, but that is beside the point for this illustration, the point being that you can have an effect on selected area(s) of the tone curve. But like I've said previously, I have found it difficult to use - easy to get wrong and make the image look bad. And given what I can achieve with the sliders in SP7 I haven't felt the need to use the tone curve - and the same in Lightroom incidentally.)
(There are three points on the diagonal line beneath the one at the top which is above the line. Those three points are there to "pin" the curve to the line, so the only change is right around that top point. If you don't do this pinning the curve gets altered all the way down.)
Click on Original size to see the animation flip between versions.
--
Nick
http://www.flickr.com/photos/gardenersassistant/collections/
GardenersAssistant Photography Videos - https://www.youtube.com/channel/UCmBgEwRDfiQMYTPORSzDxvw
https://www.talkphotography.co.uk/t...-dslr-primes-a-journey-of-exploration.531050/
Interesting observations. Thanks. As to what is going on with Curves, I have just found this. (The title refers to Photoshop, but it is much broader in scope than that.)
Thank you Erik. It has been (still is actually) a great learning experience for me. I'm glad you have found it worthwhile to follow the exploration.
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