Graduated Specular Highlights

[Finste]

Hi,

I'm current trying to create graduated specular highlights on a glossy black motorcycle helmet but having limited success. I've tried feathering a large softbox, 100 x 80cm, but had no success with that. Just a solid specular highlight. I've also tried feathering a strip softbox with a translucent diffuser between. All that did was produce two areas, one bright and one not so bright. There was no graduation from specular to diffuse highlight.

Does anyone have any other ideas? I'm not averse to resorting to photoshop if necessary but would prefer a lighting based solution.

This is what I'm trying to achieve.

http://www.tranam.co.uk/Clothing/Schuberth/schuberth_S2_gloss_black.html

Regards...

 

[Garry Edwards]

Easily done. I'll try to reply in the morning, because right now I only have this B iphone

 

[sk66]

Your light source (large softbox) needs to be VERY close and, obviously, lower power setting. You may also want to use some negative lighting (black panels).

 

[Garry Edwards]

OK, now in front of a real computer
It's an easy subject to light, compared say to a lens, about which I wrote a tutorial here, but the principles are the same.
The problem is the convex shape - flat shapes are a piece of cake. With convex shapes, the light source needs to be massively bigger as well as being so close that it's almost touching.

You mention that you're using a large 80 x 100cm softbox for this but take my word for it, in this context that softbox, which is medium at best, is small.

Your example photo was in fact lit with 3 separate softboxes, or possibly silks and you need to do the same. Silks would be better, simply because they can be much bigger and because it's also easier to light them unevenly, but it can be done with softboxes.

Done properly, there is absolutely no need for any PP work, but using the shadows/highlights tool in PS can help to turn a good shot into an outstanding one.

 

[HoppyUK]

Just guessing really, but looking at your linked image and also the other helmet pics almost certainly shot at the same time, I'm thinking that maybe a light tent has been built for the shoot, to get that all-round specula reflection - the end result basically the same idea as Garry is suggesting. Then there's a lot of Photoshop smoothing and cleaning up too.

 

[Phil V]

When I read Garry's response re silks, I pictured in my mind a recent BTS shot I saw from a music vid. Then I remembered I recently bought a new shower curtain pole, and inside the box was a white shower curtain (it nearly went straight in the bin) Perfect for something like this, or cheap white muslin background stretched on a frame and lit from behind with a softbox.

 

[Garry Edwards]

Yes, plain white shower curtains make good silks.
Silks don't get used by many amateurs, perhaps they're too useful or just too cheap, or maybe it's just because they don't have a big red L written on them

But people like me use them a lot, it's the best way there is of creating a deliberately uneven light source.

 

[Finste]

OK, now in front of a real computer
It's an easy subject to light, compared say to a lens, about which I wrote a tutorial here, but the principles are the same.
The problem is the convex shape - flat shapes are a piece of cake. With convex shapes, the light source needs to be massively bigger as well as being so close that it's almost touching.

You mention that you're using a large 80 x 100cm softbox for this but take my word for it, in this context that softbox, which is medium at best, is small.

Your example photo was in fact lit with 3 separate softboxes, or possibly silks and you need to do the same. Silks would be better, simply because they can be much bigger and because it's also easier to light them unevenly, but it can be done with softboxes.

Done properly, there is absolutely no need for any PP work, but using the shadows/highlights tool in PS can help to turn a good shot into an outstanding one.

I had a feeling It may down to size but have never seen a softbox much larger than the one I have, hence my question. Never thought of using sheets as diffusers on the scale you are suggesting. Shower curtains are obviously cheap enough to give it a go.

Just guessing really, but looking at your linked image and also the other helmet pics almost certainly shot at the same time, I'm thinking that maybe a light tent has been built for the shoot, to get that all-round specula reflection - the end result basically the same idea as Garry is suggesting. Then there's a lot of Photoshop smoothing and cleaning up too.

I take your point about the light tent but the example linked to was to illustrate the level of light fall off I was looking for. I'm not necessarily looking to replicate that image. As for Photoshop, I'm not surprised that it may have been 'shopped but then again, few images these days are not 'shopped to some degree. That is the least of my worries though as I'm trying to get my head around lighting difficult subjects and get a feel for the scale of what is involved and how to solve the problems encountered.

Thanks to all who answered, I've got a way forward with this now.

Regards...

 

[Finste]

Just in case anyone comes across this thread in future, let me state that the shower curtain worked a treat. I've got to iron out all the creases in it but it looks so much better than it did before. Even allowing for the creases it is quite obviously a very smooth graduation that can be controlled by feathering the softbox. Don't know if it made a difference but I used an Elinchrom 130x50 strip box this time rather then the wider one.

Again, thanks to all who contributed.

Regards...

 

[Garry Edwards]

Well, you now know how it's done, using a silk to create the right kind of uneven lighting and a really large light source - I'd call that a result. As for the type of modifier used to illuminate the silk, it's just down to knowledge and/or trial and error. I must have used just about every type of modfier there is to get different effects.

 

[sk66]

Well, you now know how it's done, using a silk to create the right kind of uneven lighting and a really large light source

Garry, I'm not understanding why you are saying to create an uneven light source. I understand why you might want to (i.e. put the hotspot further forward to compensate for the curve of the object/distance change). But it seems to me the lighting in the example was done with large even light sources. Am I missing something?

Unless you're just saying it that way because it's very difficult to light such a large panel exactly evenly....

 

[Garry Edwards]

Garry, I'm not understanding why you are saying to create an uneven light source. I understand why you might want to (i.e. put the hotspot further forward to compensate for the curve of the object/distance change). But it seems to me the lighting in the example was done with large even light sources. Am I missing something?

Unless you're just saying it that way because it's very difficult to light such a large panel exactly evenly....

OK...
If you wanted to create a diffused specular highlight of a flat surface, you could light the entire surface evenly (given a large enough and close enough light source) and the 'spare' light that extended beyond the subject would simply disappear - more or less.
But, do the same thing on a convex surface and there is absolutely no way of lighting the whole thing with a single light, the convex surface forces the specular reflection into a much smaller area. And what you inevitably end up with is a reflection of the light source (usually a softbox) that has hard edges, the exact opposite of what you want.

So, use a large light source such as a silk, light it unevenly so that the specular highlight is graduated and the light tails off in intensity as it nears the edges, it's far from natural but it ends up looking natural.

Also, it the subject has a strong convex shape then, bearing in mind that the light source has to be extremely close, parts of the subject are substantially closer to the light source than others and because of this there is a dramatic fall off in light intensity due to the effect of the inverse square law. Lighting the silk unevenly can take care of that problem too.

It can all be done with softboxes, but it's just easier to do it with a silk.

 

[sk66]

And what you inevitably end up with is a reflection of the light source (usually a softbox) that has hard edges, the exact opposite of what you want.

This I understand.... convex surfaces see a whole lot of area.

Lighting the silk unevenly can take care of that problem too.

And this I understand...it's what I meant by "compensate for the curve."

light it unevenly so that the specular highlight is graduated and the light tails off in intensity as it nears the edges

But this part not so much... I mean, an even light source (of sufficient size) should fall off gradually automatically due to the inverse square thing.
Maybe it would be better said as "there's no need to light it evenly?" Because if the hot spot is of sufficient size and placed correctly the silk takes care of the rest...

on a convex surface and there is absolutely no way of lighting the whole thing with a single light

And this I agree with... but if you can create one you can create others... and you could blend images if you are tight on space/gear.

 

[Garry Edwards]

This I understand.... convex surfaces see a whole lot of area.


And this I understand...it's what I meant by "compensate for the curve."


But this part not so much... I mean, an even light source (of sufficient size) should fall off gradually automatically due to the inverse square thing.
Maybe it would be better said as "there's no need to light it evenly?" Because if the hot spot is of sufficient size and placed correctly the silk takes care of the rest...


And this I agree with... but if you can create one you can create others... and you could blend images if you are tight on space/gear.

I think you may be thinking this through just a bit too much.
As all light follows the immutable laws of physics, in theory it's possible to do a Sheldon Cooper and write it all down on a whiteboard and then just leave others to follow the formulae, but in the real world it doesn't happen like that and we improvise, make it up as we go along, experiment and sometimes come up with new approaches on the fly.

For example, I take account of the ISL but I don't rely on the laws of either intended or unintended consequences, I will use uneven lighting as necessary to get the effect I want, it's quicker, easier and usually better.

Other than that, I think we're just talking semantics, maybe I should have used different words, or used them more carefully. Or maybe I should have had more interest in English and less in Physics

 

[sk66]

Other than that, I think we're just talking semantics, maybe I should have used different words, or used them more carefully. Or maybe I should have had more interest in English and less in Physics

OK. I wasn't trying to be difficult, I thought maybe I was learning something new...

 

[Garry Edwards]

OK. I wasn't trying to be difficult, I thought maybe I was learning something new...

Nor was I, just trying to explain my thought processes

I actually enjoy it when people question me, it demonstrates that they aren't in the camp of "Let's stick a hotshoe flashgun on the cheapest stand I can find, stick a £10 umbrella over it and turn out professional portraits"

 

[sk66]

"Let's stick a hotshoe flashgun on the cheapest stand I can find, stick a £10 umbrella over it and turn out professional portraits"

TBF, I think excellent results can be achieved using (relatively) inexpensive flash equipment in many situations.
But if you've done that, and also used "professional lighting," then you understand the difference.... It was a long time before I knew what a "large softbox" really was, and how marginal the 30-40" modifiers really are.