How do you find right plane/perspective to place a product on a photo?

Question

Someone on GD.SE commented that I don't know how light and perspective works. Moreover, the product I placed here near plant is in wrong plane.

How do I know if it's right or wrong plane and perspective? Is there any way so we can know how should you take the picture that fits perfectly in terms of plane and perspective, here?

PS: I know the shadow angle is not right. I got to know about this in this question. Now the question is about finding right perspective and right angle, like:

a) If the box was actually a part of this photo, would the top face of box be more visible or less than present

b) Is the actual photo taken from a more distance than the distance used for taking photo for box. In other words, is the photo of box taken from too close or too far distance

c) Should the bottom/top of box have been narrower/wider than the other end

If you can't understand, please comment, I'll edit again.

Answer 1

Match what's there in most instances and whenever possible.

The light is stationary, therefore all object should cast the same angle shadow. The closer together objects are, the similar the shadow angle will be. Based on the plant in that photo, the primary light source is almost directly in front of the plant.

If you draw lines to indicate the shadow on the plant, then transpose those lines to the box, you can see the angle of the box's shadow is incorrect --- I only drew ONE green line, then copied it. So the angle is the same....

You currently have the shadow of the box as if there's a different light source (orange lines)... As if the light source is a bit to the left and not directly in front.

(And the box shadow should have a brownish tint. Similar to how the plan't shadow is slightly brown. Brownish because both objects are relatively the same color. If the box were a different color, that would warrant a different tint to the shadow.)

Answer 2

Someone on GD.SE commented that I don't know how light and perspective works. Moreover, the product I placed here near plant is in wrong plane.

In this scene, the viewer has the perception of looking slightly down onto the bench top. In other words, the horizon, if you could see it, would be high in the image. So the top face of the box, sitting well below the horizon, should be visible, even if only slightly.

edit: the horizon, in two-point perspective, is the place where perspective lines converge. The bottom edge of the box is doing a acceptable job of matching the scene:

But perspective lines extended from the top of the box don't match. The red lines should meet at the triangle corners.

It's hard to make a convincing image without guides. Corrected perspective lines to aim for:

…Is there any way so we can know how should you take the picture that fits perfectly in terms of plane and perspective, here?

Not easily.

But if you can reshoot the scene (and not the box), then try and lower the camera to be in line with where top of the box would be. Use a dummy box if possible.

If you can reshoot the box (and not the scene), raise the camera to show more of the top face of the box.

You should expect to test a few angles until you find the right one, so leave the camera in place while you do a test composite, to make it easier to find the right angle.

b) Is the actual photo taken from a more distance than the distance used for taking photo for box. In other words, is the photo of box taken from too close or too far distance

The camera is too close to the box, because the difference in perspective between the top and bottom faces is more extreme than in the scene.

Answer 3

I'm going to say that I think it's most crucial to be thoughtful in what you use to set up your assumptions about the perspective planes in a given image: remember all parallel lines should correctly converge on a vanishing point.

In my case, I also 'cheated' a little, in that for the right-hand vanishing point (for which we have the least reference data) I was able to to make an educated guess based on the minor axis of the ellipse generated by the assumably-circular pot - and so this is the perspective setup I generated:

As you can see, though Vikas came pretty close by eye, the inaccuracy leads to a perceptible sense of the box being 'tipped' relative to the counter's plane - also, having a correctly-defined plane will allow more accurate shadow-casting once you get to that task - you can instantly see here why the shadows' line seems so wrong - it is.

To correctly cast a shadow, you must set the light/shadow casting angle (cardinal on the groundplane) and the light source's relative elevation to set the vertical casting angle too - once you're set that as a figure, you locate it at a casting corner of your given form, then you intersect that downwards angled line with the on-the-plane cardinal line and where those intersect is one node of your shadow - you repeat this for all your casting corners, then draw the contour that those points make - and there's your cast shadow's shape on the base plane - then you figure out the degree of umbra based on how far away the light source is.

Hope this helps some.

Answer 4

Apart from answer below you also put a box in perspective that is not playing well with chosen background. Maily due to lack of any edge on the pot and only (almost) two planes the brain is expecting a central persective

While your box is forcing vanishing point to be on the left

You can of course force two vanishing point in picture but you would need to move the box to most close edge in the central part of picture and the right lover edge to play correctly with the table VP. When you could find that the box need to be very big or even cover the pot making no sense in choosing such photo in the first place.