[simmsimaging]

Josh - I think your test has actually demonstrated my comment: which is the closer lights are probably going to be softer, not higher contrast. It is a bit misleading to think of it in terms of distance though, because it is not really distance that is the factor but rather relative size of the lightsource and how much of the subject it covers and how much self-occlusion occurs etc.

The brightness factor is logical as you pointed out - every time you halve the distance you double the brightness so you should have to stop down the lens as you bring the light in closer.


In any case, the bottom line is that you can control your contrast this way but if you wish to avoid hassles with exposure just work with the size of your emitters instead - it will give you much the same thing.



b

[lsega77]

Hmm interesting...

Thanks for the test Josh!

This actually confuses me a little but I think I know why.

In my mind, logic says that the closer a light is to a subject the more light it can emit onto the subject since less light is able to falloff/dissipate over a given distance. In other words, the closer the light the 'hotter' the hotspot on the subject.

In a way your test contradicts that theory but you're also compensating in each shot to achieve the same exposure. If both test were done with the f-stop the same I think we would see the light 'seemingly' brighter in the first shot than in the second.

The second shot does seem to me to have more contrast then the first though. Nice reflections on the gold material BTW.

I do like this test though as it does show me a different way to control the light intensity for a shot. I had typically been doing this through adjusting the ISO post render.

Luis

BTW - NY! My old stomping grounds! What part? I'm a displaced Manhattanite myself

[joshh]

Brett- Your observations are very clear and practical.I think the confusing term here though is 'contrast'. When a light is smaller or farther away the transitions from light to dark are more abrupt and closer or larger lights give more gradual transitions from light to dark. When I checked in photoshop however, I found that there was a greater dynamic range of light and dark RGB values in the softer image so technically I guess it has more contrast. The most important thing of course is to please the eye and get a nice looking image.

Luis- My test was based on getting the exact same exposure with one light in two different positions, that is why I changed the f-stop. I just wanted to show what happens to the quality of light and the percieved contrast. It's also interesting to see what happens to the reflections.

I'm in midtown near MSG. How long did you live here? I wouldn't mind getting displaced myself, I've been here too long !

[simmsimaging]

When I checked in photoshop however, I found that there was a greater dynamic range of light and dark RGB values in the softer image so technically I guess it has more contrast.

This is what I was talking about when I said this:

One thing you may run into is the quality versus quantity issue with tonal range. More is often better, but it really depends on the subject. Flatter lighting tends to bring out shadow and highlight details - giving you a broader visisble range, but it's not always what gives you the best image.

The best image is the one that has the best control of the *differences* between the tones in the shot, however many there are. That said, I think you should generally strive to have something very close to white and something very close to black to ensure the overall shot has a feel of good contrast, but how many tones occur in between depends on subject, lighting, and aesthetic.

To some degree you are confusing tonal range and contrast. They overlap for sure, but they are not the same thing. A broad tonal range is good, but not at the expense of contrast. You can have 100000 shades of grey in there, but without some contrast it's all just shades of boring mud - most of the time.

This is one of the hard parts of good photography and imaging work: maintaining good tonal range *and*contrast. Most people end up with one or the other.

Anyway, in general parlance contrast is a measure of difference in tones so the smaller/distant light will give you more contrast.

b

[joshh]

well said Brett !