Image manipulation (power of shadows and lights)

[Nordin]

Hey!!!

The strength of dealing with shadows and lights when it comes to putting together several pictures realistic is huge. If you can see where it's needed lighting / shadows, then the whole process gets much easier!
Ask questions like:
When the object get close to the objects what kind of strength of shadow should I add?
How quickly it fades out?
What different brightnesses my pictures has?

use the doge tool, burn tool, different brushes, play around with the opacity, curves and so on...

I made an example with three different images. The first picture is of the armchair, the second a lion and the third on the girl...

Certainly many more who are good at this that has some good tips!

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[Vetoed]

Should there be light on the right side of the woman? also im sure that the arm of the seat would cause the light of the tiger to be not as strong imo

 

[Nordin]

Yes exactly, good thought. However, we dont know the conditions of the room's right side, so it could be the light from there ...
But then the question is whether you think the shadows on her legs is correct for example.

But I cant agree with the light on the tiger. My opinion is that the light and shade is relatively accurate. The armrest affect his tail but not himself.

 

[Paul]

Needed to warp the cushion under the lion cub a bit, just to give the impression (no pun intended):mrgreen:

 

[Crotale]

your light sources are inconsistent. I did some calculations to show where your light sources are derived. I used the Threshold command to show light and dark areas. I also used the Equalize function to alleviate the extreme differences in lighting and then overlaid the Threshold effect to show that the lighting still shows the same source locations.

Note the overhead view of the lights. The room lighting comes from the foreground and up fairly high. The sun lighting in the tiger photo came form the animal's proper right and appears to be at least a couple of hours before/after high noon. A high spotlight was used in front of the girl for lighting effect. The wall and floor to the girl's proper left should be flood illuminated.

You can correct these issues by using a mixture of dodging and burning as well as painting in the light. You may have to use some color matching on the girl's skin to get a more neutral lighting on her face and shoulders.

Hope this helps.

 

[IamSam]

The light source may be slightly inconsistent, but it's acceptable. I perceive it as a secondary light source. I totally agree with Paul here in that a Lion cub of that size would weigh somewhere between 60 to 80 lbs if not more. The Lion cubs weight would be affecting the chair cushion significantly. The shadows on the chair being produced by the Lion cub are off to me, both on the cushion and the arm of the chair...maybe a bit long and diffuse for the light source.

 

[iDad]

I am not getting into the lighting issues but I will mention the floor it looks to me as though the chair is being looked at straight on the floors perspective is an upward slant as though the chair with slide right down

 

[Tom Mann]

Hi Crotale -

Unfortunately, unless I am missing something very fundamental, I don't think your method works (at least without substantial human "over-riding").

Basically, you are trying to separate the irradiance (the distribution of the intensity and direction of light in the scene) from the reflectivity of the various surfaces in the scene. This is a laudable undertaking, and is a well known problem in optics, machine vision, image analysis, etc. There have easily been thousands of papers written on it, e.g., "Inverse Global Illumination: Recovering Reflectance Models of Real Scenes from Photographs" out of the CS Dept at UC Berkeley.

If the simple procedure of thresholding or luminance equalization followed by thresholding worked to any degree, it would be incredibly useful, known to everyone in the field, and probably even incorporated into programs like PS. It is not.

As a concrete example of one way such a simple method could produce erroneous results, consider the original woman in this scene. Imagine that she was replaced by a statue of black obsidian draped in a white gown. With a subject like this, both variants of your method would not suggest that there should be an arrow coming in from the left towards her right shoulder (as it was with normal skin), even though the lighting had not changed one iota, only the reflectivity of her skin.

Cheers,

Tom

 

[ibclare]

I agree that there are primary and secondary light sources and it is a challenge to get differently lighted subjects to look 100% plausible. That said, I think this is pretty close. There is an area that bothers me. It is within the red rectangle below.



The legs of the chair are brightly highlighted. The leg and especially the foot do not indicate that they are struck by that light source (suggested by white). The way I see it, there should be more shadowing (the blue), both of the dress which dips into shadows between the model and the chair, and of the chair which is obscured partially by the leg and foot -- see the green line which shows that the foot is further forward than the leg of the chair. The foot is definitely lacking in detail and light.

I also wonder if the scale of teh model is just slightly off, a bit large for the chair. But now I'm getting nitpicky! My eyes are crossing.

That said, I like the manipulation, the idea is cute.

And BTW Nordin, nice to see you; seems like it's been awhile . . .

 

[Crotale]

Tom, I was not using any function or feature to override or manipulate the lightning, but merely showing a basic offset to all the light sources that work to impede a believable composite. I suppose I miscommunicated my intent, which was merely to provide one method of lighting analysis.

 

[Tom Mann]

Hi Crotale - I understood perfectly that you were not overriding or manipulating the lighting and that you were trying to provide an analysis method.

The problem I was pointing out is that particular analysis method just doesn't work in anything approaching a reliable fashion.

Tom

 

[Crotale]

Hi Crotale - I understood perfectly that you were not overriding or manipulating the lighting and that you were trying to provide an analysis method.

The problem I was pointing out is that particular analysis method just doesn't work in anything approaching a reliable fashion.

Tom

The point I was trying to make was that each object appears to have unique lighting and that my method shows that to some notable degree, even after equalizing the extremes. Multiple lighting would affect more than a singular object in a room such as the one in the depiction and that just isn't the case here. I simply thought I was being clever at finding a way to point it out.

Yes, you would have to use human judgment to consider the colors involved as well, such as normally lighter and darker colors overall affect the threshold application. As you stated earlier, there is no automated function for doing this.

You can make excuses that the current lighting setup doesn't have affect the overall consistency of the image; I disagree.

Edit: And the arrow coming in across her right shoulder was not indicating lighting from that respective azimuth, but an angle looking down towards her. You must have overlooked my overhead layout of possible light source directions (rough, but meant to be to scale).

But...whatever. It isn't worth my time to offer up help that is so obviously wrong.

 

[Nordin]

Needed to warp the cushion under the lion cub a bit

I agree!
Thanks for the great response! Will continue working on the picture and we'll see if we approach a final result
Want to be good at working with lights and shadows in PS. So this helps!

And BTW Nordin, nice to see you; seems like it's been awhile . . .

nice to see you too
Much at work so not much time for Photoshop

 

[ibclare]

Great. Post your results when you can get around to them. You can keep it in this thread for clarity if you like.

Now, if you can find one of the time re-winders like Hermione Granger used, you can play in Photoshop to your heart's content. Try ebay!