Gelling CITI600 / Godox AD600

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I was just trying to workout how I would gel the CITI600, been through a few videos until I found one that actually seems optimum - easiest to make and store

Here's the video, but basically

Cut gel into a + shape, the centre of the + goes over the end of the bulb and you use an elastic band to secure it as you wrap round the four points - careful not to cover the ventilation holes.

View: https://www.youtube.com/watch?v=-wjuvHurztA

Just like this
https://www.ebay.co.uk/itm/FlashGel...871956?hash=item3d402faf54:g:2Y4AAOSwcB5ZG4ny

But it seems expensive!!!!
 
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I was just trying to workout how I would gel the CITI600, been through a few videos until I found one that actually seems optimum - easiest to make and store

Here's the video, but basically

Cut gel into a + shape, the centre of the + goes over the end of the bulb and you use an elastic band to secure it as you wrap round the four points - careful not to cover the ventilation holes.

View: https://www.youtube.com/watch?v=-wjuvHurztA

Just like this
https://www.ebay.co.uk/itm/FlashGel...871956?hash=item3d402faf54:g:2Y4AAOSwcB5ZG4ny

But it seems expensive!!!!

That's a sweet way of gelling, basically thanks to LEDs. It couldn't be done like that with hot tungsten modelling bulbs.
 
Useful, thanks, that'd work with my Superfasts if I take the modelling bulb out. It would make gelling the Lencarta pop-up softboxes a whole heap easier - the umbrella mechanism makes it tricky to put a gel inside the softbox.

.. though I wonder how much difference the uncovered parts would make? I usually go to a lot of trouble to ensure there is no leakage.
 
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This is the way I've been gelling lights for years - I call em "hats". Robert, and his mate don't mention one the key things about working with gels though. You need the light to go through a known amount of gel. There is no standard for this, however, most photographers working with gels typically pin a gel sheet to a 7" reflector and then bounce that into something if they need a larger light source. So, the area (3.5^2*Pi) = 38.5 square inches is the "normal" or typical amount of gel the light goes through. If you gel an entire 3 foot square softbox for example, and pump the same light output through it, the colour will be more saturated. So, when making my hats (and really, you don't need a bendy ruler to measure the circumference of the dome - you can use... maths! Pi*diameter will give the circumference) I use a piece about the same area as for a 7" reflector. Actually, a bit more tbh, as I like saturated colours, and often end up doubling up the gels on the reflectors. The piece in the video looked a bit small - which will result in a fairly weak colours (this is not wrong as such - you may want those pastel shades - just something to be aware of).

He and his friend have also missed a trick in making these really practical in the studio. When I'm shooting, I like to work fast, not just to get stuff done, but also for the sake of the model who's on set while I'm making adjustments to the lights. I get faster as the day goes on and by the last set, I'm just abandoning stuff all over the place to shoot more variations on the theme, or tweak something or other. The studio typically looks like an explosion in a lighting warehouse when I've finished... I don't have time to fiddle about with elastic bands on-set. I make my hats beforehand by just wrapping a piece of gel of roughly the right area around the glass dome on my SF600s and then I tape the seam with Sellotape. Then I fold over the excess gel and tape that down too. I make sure it's a bit loose on the dome and then I can just re-use these hats without any fiddle at all - they just slide on. I'll then typically attach the modifier first, and then fit the gel hat. It's a really fast way of swapping colours in and out, and works with any modifier.

IMG_4181.jpg

Just one caveat to all of this - the heat, on the gel, but more importantly on the tube/light. I use Rosco or Lee high temperature gels. I buy them in big sheets, usually from Stage Depot https://www.stagedepot.co.uk/lighting/lighting-gel . Unlike the AD600, my SF600's have incandescent 150W modelling lamps. I turn these off when using gels, however I have been caught out once or twice, where the settings on the trigger have overridden the settings on the light and the lamp has come back on and cooked the gel. However, even after a solid hour at gas mark 4, once the dome cools again, the high temp gels un-stick. I'm also normally using the lights on half power or below - and you do need to be mindful of how much flash energy you're pushing through the gel, and the higher heat build up on the tube. Make sure you leave at least some of the ventilation on the glass domes uncovered, and don't pound the light at full power relentlessly :p If I'm using a reflective umbrella (and I've been having a bit of an umbrella renaissance recently :p ) I will just use a gel sheet over the 7" reflector in the "normal" way.

Some results (Model in bra and pants set - no nudity but probably not 'safe for work')
https://www.flickr.com/photos/owenlloyd/40561352412/in/dateposted-public/
https://www.flickr.com/photos/owenlloyd/39688778865/in/dateposted-public/
https://www.flickr.com/photos/owenlloyd/26498534208/in/dateposted-public/
 
Robert, and his mate don't mention one the key things about working with gels though. You need the light to go through a known amount of gel. There is no standard for this, however, most photographers working with gels typically pin a gel sheet to a 7" reflector and then bounce that into something if they need a larger light source. So, the area (3.5^2*Pi) = 38.5 square inches is the "normal" or typical amount of gel the light goes through. If you gel an entire 3 foot square softbox for example, and pump the same light output through it, the colour will be more saturated. So, when making my hats (and really, you don't need a bendy ruler to measure the circumference of the dome - you can use... maths! Pi*diameter will give the circumference) I use a piece about the same area as for a 7" reflector. Actually, a bit more tbh, as I like saturated colours, and often end up doubling up the gels on the reflectors. The piece in the video looked a bit small - which will result in a fairly weak colours (this is not wrong as such - you may want those pastel shades - just something to be aware of).

I keep coming back to this... I am too addled with opiates to do the maths and too injured to do a test but I don't think it's true.

It's notionally appealing that the inverse square law would apply to gels too but... I'm not convinced that gel efficiency is affected by the number of photons hitting it. The chance of any given photon getting through a gel is the same no matter how many other photons there are, surely?
 
I keep coming back to this... I am too addled with opiates to do the maths and too injured to do a test but I don't think it's true.

It's notionally appealing that the inverse square law would apply to gels too but... I'm not convinced that gel efficiency is affected by the number of photons hitting it. The chance of any given photon getting through a gel is the same no matter how many other photons there are, surely?
Let's not overthink this, it's actually very simple, and works like this.
1. All light is additive, therefore if you add more light, the light gets brighter and the light from the gel becomes more pastel, or less saturated if you prefer.
2. Pastel gel colours can only produce pastel results.

Therefore, if you want strong, saturated colours all that you need to do is to:
1. Use strong, rich gel colours
2. Use the minimum possible amount of lighting power.
 
Let's not overthink this, it's actually very simple, and works like this.
1. All light is additive, therefore if you add more light, the light gets brighter and the light from the gel becomes more pastel, or less saturated if you prefer.
2. Pastel gel colours can only produce pastel results.

Therefore, if you want strong, saturated colours all that you need to do is to:
1. Use strong, rich gel colours
2. Use the minimum possible amount of lighting power.

So.. are you saying that gel area makes a difference or makes no difference?
 
So.. are you saying that gel area makes a difference or makes no difference?
Well, of course it makes a difference, but unless you want the deepest possible saturated colours the ge really doesn't need to totally enclose the light source.
We went through this with Owen, 2 or 3 years ago, when he did a shoot at the Lencarta studio. He likes his gels and used a complex system of fitting a gel to the outside of a metal beauty dish, using what were basically clothes pegs to completely enclose the light - I used a bit of sticky tape to fix the gel to the top of the beauty dish and let it hang down, much quicker and easier, and the same result.
 
Sorry, I'm clearly not explaining myself very well. I'll blame the painkillers & try again.

Consider two situations:

1. Light at full power in a softbox, gelled with a single layer of gel to completely cover the flash tube, gel inside the softbox as close to the bulb as possible.
2. Light at full power in a softbox, gelled with a single layer of gel over the front to completely cover the entire softbox.

Owen's contention is that the former will yield more saturated colours.

From a physics perspective I can't see why that would be.
 
Sorry, I'm clearly not explaining myself very well. I'll blame the painkillers & try again.

Consider two situations:

1. Light at full power in a softbox, gelled with a single layer of gel to completely cover the flash tube, gel inside the softbox as close to the bulb as possible.
2. Light at full power in a softbox, gelled with a single layer of gel over the front to completely cover the entire softbox.

Owen's contention is that the former will yield more saturated colours.

From a physics perspective I can't see why that would be.
Nor can I.
 
So.. are you saying that gel area makes a difference or makes no difference?
Pushing the light through a smaller area (smaller gel) has the same effect as increasing the power for a larger area (larger gel). Gels are subtractive, they don't actually color the light. The reason a red gel looks red is because it blocks all other colors of light. So if you push more through (or use less gel) you get a red of higher luminance (less saturation).
 
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Pushing the light through a smaller area (smaller gel) has the same effect as increasing the power for a larger area (larger gel).
If you gel an entire 3 foot square softbox for example, and pump the same light output through it, the colour will be more saturated.

Why?

If a normally distributed sample of 1000 photons hits a small gel close to the tube then (say) 50% will have a wavelength which causes them to be blocked.
If a normally distributed sample of 1000 photons hits a large gel close far from the tube then (say) 50% will have a wavelength which causes them to be blocked.

The end result is the same - 500 photons get through.

The distribution of those photons is a separate matter and that can affect the saturation.
 
Sorry, I'm clearly not explaining myself very well. I'll blame the painkillers & try again.

Consider two situations:

1. Light at full power in a softbox, gelled with a single layer of gel to completely cover the flash tube, gel inside the softbox as close to the bulb as possible.
2. Light at full power in a softbox, gelled with a single layer of gel over the front to completely cover the entire softbox.

Owen's contention is that the former will yield more saturated colours.

From a physics perspective I can't see why that would be.

I haven't actually tried it, but I'm with Garry - it makes no difference.

I can't see how it would, based on similar experience with ND filters and gels. If 100% of the light is forced through a one-stop ND filter/gel, you get one-stop reduction in brightness. Doesn't matter if the gel is a couple of inches wide over a speedlight, or a couple of feet square over a softbox, or indeed over the lens.
 
Why?

If a normally distributed sample of 1000 photons hits a small gel close to the tube then (say) 50% will have a wavelength which causes them to be blocked.
If a normally distributed sample of 1000 photons hits a large gel close far from the tube then (say) 50% will have a wavelength which causes them to be blocked.

The end result is the same - 500 photons get through.

The distribution of those photons is a separate matter and that can affect the saturation.
The math doesn't work because this is an area where the primary concern/behavior is that of light as a wave and not as a particle/photon (light is both). The best correlation I can make is to think of a gel as a "color gobo". If the gobo is placed close to the light source it's effect is much softer and more diffused by the time it reaches the subject because it has more time/distance to spread out/mix (as waves) before reaching the subject. In both cases it is blocking some light and letting some light through, but it's effective density is varying.
Color filters do the same thing...they block (filter) some light and let some light through depending on their density, and their effective density relates to the distance to the subject; and therefore their distance from the light source.

Essentially, a color filter doesn't filter 50% per area, but rather 50 per area (i.e. a fixed amount, using arbitrary numbers). So in the near filter case 200 photons/area hit the filter and 150 pass unfiltered while 50 are filtered. In a 2x distance scenario 50 photons/area hit the filter and all 50 are filtered. If this wasn't the case the saturation would not vary depending on how much light you pushed through it... it would always be 50%. But if you take a flashlight and hold it a fixed distance from the wall while moving a filter between them (changing the distance from the light) you will see that it's effective density varies greatly (the ratio is the same ISL).
 
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I haven't actually tried it, but I'm with Garry - it makes no difference.

I can't see how it would, based on similar experience with ND filters and gels. If 100% of the light is forced through a one-stop ND filter/gel, you get one-stop reduction in brightness. Doesn't matter if the gel is a couple of inches wide over a speedlight, or a couple of feet square over a softbox, or indeed over the lens.
Yes, but 1stop is not necessarily half... it is always 1 stop (i.e. a fixed amount and not a percentage). If you push more light through it, then more goes through unfiltered. Distance affects it the same way.

Start with 4 at the source, over distance it spreads out to 1/area (1/4) and then you subtract the 1 using a larger filter... the result is 0
But if you start with 4 and subtract the 1 immediately using a smaller filter you have 3, which then reduces to 1/4 over the same distance... the result is .75
 
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The math doesn't work because this is an area where the primary concern/behavior is that of light as a wave and not as a particle/photon (light is both). The best correlation I can make is to think of a gel as a "color gobo". If the gobo is placed close to the light source it's effect is much softer and more diffused by the time it reaches the subject because it has more time/distance to spread out/mix (as waves) before reaching the subject. In both cases it is blocking some light and letting some light through, but it's effective density is varying.
Color filters do the same thing...they block (filter) some light and let some light through depending on their density, and their effective density relates to the distance to the subject; and therefore their distance from the light source.

Essentially, a color filter doesn't filter 50% per area, but rather 50 per area (i.e. a fixed amount, using arbitrary numbers). So in the near filter case 200 photons/area hit the filter and 150 pass unfiltered while 50 are filtered. In a 2x distance scenario 50 photons/area hit the filter and all 50 are filtered. If this wasn't the case the saturation would not vary depending on how much light you pushed through it... it would always be 50%. But if you take a flashlight and hold it a fixed distance from the wall while moving a filter between them (changing the distance from the light) you will see that it's effective density varies greatly (the ratio is the same ISL).
I think that you could be confusing yourself here by overcomplication.
Don't give any thought to the screening (filtering) effect of the gel, because it isn't relevant to this - it doesn't matter whether the light that reaches the measurement point falls within the visible spectrum or not, because it will still be there whether we can see it or not.
And it doesn't matter whether the light is in the form of waves or particles (photons) because quantum physics tells us that both/either end up exactly the same - one of the very few things that Einstein got wrong.

The simple fact of the matter is if there is some kind of filter or other barrier that interupts and modifies the light on its passage from point A to point B, for all practical purposes it doesn't make any difference whether the light source is enclosed or whether the barrier only covers the entirety of the 'open' area and the light taht doesn't hit it directly is reflected or controlled in some other way.

Now, Owen has his own way of doing things and they seem to work for him, but his views are not supported by the physics. He believes that his 'hats' are in some way better, and of course he is not the first to say this, for example various manufacturers have made strong claims about 'gels' which, for their own convenience or possible to try to gain some kind of spurious marketing edge, have been supplied as hats or sleeves. Even the crappy Portaflash lights of yesteryear had coloured plastic caps that fitted over the flashes, with strange claims made about their efficacy. All that I can tell you, as a retired advertising photographer, is that all advertising is lies:)
This is the way I've been gelling lights for years - I call em "hats". Robert, and his mate don't mention one the key things about working with gels though. You need the light to go through a known amount of gel. There is no standard for this, however, most photographers working with gels typically pin a gel sheet to a 7" reflector and then bounce that into something if they need a larger light source. So, the area (3.5^2*Pi) = 38.5 square inches is the "normal" or typical amount of gel the light goes through. If you gel an entire 3 foot square softbox for example, and pump the same light output through it, the colour will be more saturated. So, when making my hats (and really, you don't need a bendy ruler to measure the circumference of the dome - you can use... maths! Pi*diameter will give the circumference) I use a piece about the same area as for a 7" reflector. Actually, a bit more tbh, as I like saturated colours, and often end up doubling up the gels on the reflectors. The piece in the video looked a bit small - which will result in a fairly weak colours (this is not wrong as such - you may want those pastel shades - just something to be aware of).

Actually, doubling the same colour of gel does nothing that reducing the amount of light passing through it doesn't do - if you've already filtered out everything except, say, red then adding another layer of red won't filter out any other colours, because they aren't there. There's nothing wrong with using more than one gel, but there is no point if they are the same, they need to be different in order to filter out additional colours.
 
The simple fact of the matter is if there is some kind of filter or other barrier that interupts and modifies the light on its passage from point A to point B, for all practical purposes it doesn't make any difference whether the light source is enclosed or whether the barrier only covers the entirety of the 'open' area and the light taht doesn't hit it directly is reflected or controlled in some other way.
Yes. But light intensity/density is a factor, and distance affects that.

Using a simple online RGB color picker to demonstrate.

Let's say the filter in question is a magenta filter that blocks out all of the green and passes 90% of the red and blue wavelengths. Those are "the fixed amounts" I noted earlier (as opposed to % of photons).
If we start with a light source that puts red at 255 and blue at 200 we get this shade of magenta.
Screen Shot 2018-03-23 at 2.19.01 PM.png


If we then reduce the light intensity/density so that they are both reduced by 20% respectively we get this shade of magenta (assuming a color stable source).
Screen Shot 2018-03-23 at 2.27.40 PM.png

We can reduce the intensity/density per filter area with power or distance and it won't matter, the result is the same (changing the intensity/density of the light is the same as changing the density of the filter). But power adjustments are typically **much more significant, and certainly easier to do than changing distance is. What we can't change is the fixed amount of filtering per area that occurs.

None of this usually matters because we really only care about a net change/result.
 
Yes, but 1stop is not necessarily half... it is always 1 stop (i.e. a fixed amount and not a percentage). If you push more light through it, then more goes through unfiltered. Distance affects it the same way.

Start with 4 at the source, over distance it spreads out to 1/area (1/4) and then you subtract the 1 using a larger filter... the result is 0
But if you start with 4 and subtract the 1 immediately using a smaller filter you have 3, which then reduces to 1/4 over the same distance... the result is .75

"One stop is not necessarily half." What? You sure about that?!
 
"One stop is not necessarily half." What? You sure about that?!
What I meant is one stop reduction is only "half" of two stops of light. Yes, it is 50% transmission. Just like the color filter, it is transmitting less light/area at a greater distance simply because it is receiving less light, but it is (should) not affect the color/saturation of the light wave/spectrum.
I think the difference is that exposure is a complete cycle from source to sensor, so you can subtract at any point with the same result. Whereas the effect of color/saturation of the light source is primarily from source to subject.
Out of curiosity I think I will try two exposures using the zoom head thing and it's color filters (the one you also have). One with the filter over the light source, and one with it over the lens. If my understanding (and what I'm trying to convey) is correct the images should be significantly different... if they are not, then I will have to seriously rethink things.

It's not often I am adamantly wrong, but it's happened before... maybe this is something I've had wrong for a very long time (and since it hardly matters, not something I've really tested).
 
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What I meant is one stop reduction is only "half" of two stops of light. Yes, it is 50% transmission. Just like the color filter, it is transmitting less light/area at a greater distance simply because it is receiving less light, but it is (should) not affect the color/saturation of the light wave/spectrum.
I think the difference is that exposure is a complete cycle from source to sensor, so you can subtract at any point with the same result. Whereas the effect of color/saturation of the light source is primarily from source to subject.
Out of curiosity I think I will try two exposures using the zoom head thing and it's color filters (the one you also have). One with the filter over the light source, and one with it over the lens. If my understanding (and what I'm trying to convey) is correct the images should be significantly different... if they are not, then I will have to seriously rethink things.

It's not often I am adamantly wrong, but it's happened before... maybe this is something I've had wrong for a very long time (and since it hardly matters, not something I've really tested).
You're wrong, so please do carry out those tests
 
You're wrong, so please do carry out those tests

Yes.
Yes. But light intensity/density is a factor, and distance affects that.

Using a simple online RGB color picker to demonstrate.

Let's say the filter in question is a magenta filter that blocks out all of the green and passes 90% of the red and blue wavelengths. Those are "the fixed amounts" I noted earlier (as opposed to % of photons).
If we start with a light source that puts red at 255 and blue at 200 we get this shade of magenta.
View attachment 122754


If we then reduce the light intensity/density so that they are both reduced by 20% respectively we get this shade of magenta (assuming a color stable source).
View attachment 122757

We can reduce the intensity/density per filter area with power or distance and it won't matter, the result is the same (changing the intensity/density of the light is the same as changing the density of the filter). But power adjustments are typically **much more significant, and certainly easier to do than changing distance is. What we can't change is the fixed amount of filtering per area that occurs.

None of this usually matters because we really only care about a net change/result.

Too much theory and over-thinking. Not enough logic ;)

If you accept that using ND gels is the same as coloured gels in this respect, what would be the difference between:

- Putting a speedlight in a softbox, with a small ND gel sealed over the flash head,
and
- swapping the ND gel for a much bigger piece from the same sheet, sealed over the entire softbox front?

No difference. The exposures would be exactly the same.
 
Yes.


Too much theory and over-thinking. Not enough logic ;)

If you accept that using ND gels is the same as coloured gels in this respect, what would be the difference between:

- Putting a speedlight in a softbox, with a small ND gel sealed over the flash head,
and
- swapping the ND gel for a much bigger piece from the same sheet, sealed over the entire softbox front?

No difference. The exposures would be exactly the same.

Or look at it another way. If the effect of a filter depends on physical area used, then if you put say a 2-stops ND filter on a telephoto lens, it would behave differently on a wide-angle. But it doesn't, it's still two stops.
 
There's no question that pushing less light through a color filter increases it's saturation (reduced brightness). And there is no question that having the light travel farther passes less light per area (the filtration effectivity/factor doesn't change) which changes the saturation at that point. However, I see my error and I kind of indicated it in post 19 where I said "Color filters do the same thing...they block (filter) some light and let some light through depending on their density, and their effective density relates to the distance to the subject..."

But instead, the factor is the total light travel... i.e. if the filter is closer to the source and more light per area passes through, the light is less saturated (brighter) *at that point*... however, if it has to travel a greater distance it will loose that additional brightness and increase in saturation to the same level by the time it reaches the subject. If the filtration is kept at a constant distance and the light is moved closer the light will be brighter/less saturated, but again, it is due to the reduction in total light travel and not the distance to the filter.
Too much theory and over-thinking. Not enough logic ;)
Too much trying to explain what I thought I knew/understood... I don't like being wrong, but I don't have a (big)problem with admitting it when it happens.
 
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There's no question that pushing less light through a color filter increases it's saturation (reduced brightness). And there is no question that having the light travel farther passes less light per area (the filtration effectivity/factor doesn't change) which changes the saturation at that point. However, I see my error and I kind of indicated it in post 19 where I said "Color filters do the same thing...they block (filter) some light and let some light through depending on their density, and their effective density relates to the distance to the subject..."

But instead, the factor is the total light travel... i.e. if the filter is closer and more light per area passes through, the light is less saturated (brighter) *at that point*... however, if it has to travel a greater distance it will loose that additional brightness and increase in saturation to the same level by the time it reaches the subject.

Too much trying to explain what I thought I knew/understood... I don't like being wrong, but I don't have a problem with admitting it when it happens.

(y)

"There's no question that pushing less light through a color filter increases it's saturation (reduced brightness)." Yes, but that's just exposure level. The difference between red and pink, is pink is light red, over-exposed; likewise, maroon is just dark red, under-exposed.

If you put a one-stop ND filter in front of any light, it will reduce brightness by half, 50%. If there are 100 photons hitting one side, 50 photons will come out of the other. If it's 1m photons, then you get 500,000.
 
The difference between red and pink, is pink is light red, over-exposed; likewise, maroon is just dark red, under-exposed.
The difference between red/pink/maroon is a difference in the amount of blue added to red (light) or blue subtracted from white (filter/reflected)... RGB vs CMY.
I wanted to convolute the resulting color of the filtered light as being additive at the subject, but instead the cause (filter) is subtractive. And since the effects are subtractive at all points (filtered light source, subject reflectivity, filtered light received) it makes no difference what the sequence is.
 
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The difference between red/pink/maroon is a difference in the amount of blue added to red (light) or blue subtracted from white (filter/reflected)... RGB vs CMY.
I wanted to convolute the resulting color of the filtered light as being additive at the subject, but instead the cause (filter) is subtractive. And since the effects are subtractive at all points (filtered light source, subject reflectivity, filtered light received) it makes no difference what the sequence is.

That's just being picky on the semantics, and misses the point ;)
 
That's just being picky on the semantics, and misses the point ;)
Maybe... if you had said bright red (towards white) and dark red (towards black) I wouldn't have said anything. I'm not sure what point you were trying to make that I hadn't already stated/corrected...
 
Nor can I.
That's probably because it's the opposite of what I said :)

The same amount of light, through more gel, will be more saturated. It's not about being totally enclosed. If you gel the front of a softbox, that's a lot more area of gel for the light to go through, than if you gel say, a 7" reflector. If the light output from the strobe is the same, the output will be more saturated. You can get the same saturation gelling the flash tube cover, as long as you use the same area of gel to do it - ie you take a piece of gel big enough to cover a softbox and layer it on to the flash tube.
 
That's probably because it's the opposite of what I said :)

The same amount of light, through more gel, will be more saturated. It's not about being totally enclosed. If you gel the front of a softbox, that's a lot more area of gel for the light to go through, than if you gel say, a 7" reflector. If the light output from the strobe is the same, the output will be more saturated. You can get the same saturation gelling the flash tube cover, as long as you use the same area of gel to do it - ie you take a piece of gel big enough to cover a softbox and layer it on to the flash tube.
Ahh... That may be what you wrote, but it's not how it read to me, and it doesn't work that way anyway, because the size of the area gelled does not and can not make any difference.
Now, if you put 2 layers of gel in place then the result will certainly be more saturated, but this is simply because less light reaches the subject, and you would get exactly the same result by turning the flash power down by the same factor as the transmission value of the gel.

I have enormous respect for you, you're a good, artistic photographer who turns out great work that is both technically good and creative, but I think that you sometimes run into problems with the physics and reach conclusions that are based on empiricism rather than science, e.g. if you put a double layer of gel on a light and it gives you the result you want, you may then assume that it's because you put on an extra layer, or a larger piece, when in reality it's because it caused underexposure, and therefore more saturation - in the same way that you told me that exposure meter readings should be taken from the subject to the light, when we all know that they should be taken to the lens. However, if you meter to the light and you like the result, it's reasonable to assume that the methodology is correct, based on your emphirical experience.
 
Actually, doubling the same colour of gel does nothing that reducing the amount of light passing through it doesn't do - if you've already filtered out everything except, say, red then adding another layer of red won't filter out any other colours, because they aren't there. There's nothing wrong with using more than one gel, but there is no point if they are the same, they need to be different in order to filter out additional colours.

This does make absolute sense Garry I must admit. The gels are not modifying the light as such, just absorbing some frequencies, and passing others. Maybe the difference I've observed is merely a reduction in overall intensity after all! I'll test it.

(but hey those inverted clothes pegs do work (sometimes :p ) )
 
This does make absolute sense Garry I must admit. The gels are not modifying the light as such, just absorbing some frequencies, and passing others. Maybe the difference I've observed is merely a reduction in overall intensity after all! I'll test it.

(but hey those inverted clothes pegs do work (sometimes :p ) )
They work fine, but when you get to my advanced age you'll realise that life is too short to sod about with clothes pegs, and that masking tape was (or should have been) invented to do the same job in a fraction of the time, and without ever having to cut a sheet of gel :)
 
A you told me that exposure meter readings should be taken from the subject to the light, when we all know that they should be taken to the lens. However, if you meter to the light and you like the result, it's reasonable to assume that the methodology is correct, based on your emphirical experience.

I agree for the key light (or any other front light). aiming back at the camera produces the right result. I aim the meter at the light for edge or kicker lights, that are primarily behind the subject or to the side. With the meter at the subject, aimed back to the camera, it will not pick up any light, (the light will hit the back of the meter), so you really have no choice but to aim it at the light. TBH, I rarely meter these lights though as I've found over the years that I rarely end up using that value.
 
I agree for the key light (or any other front light). aiming back at the camera produces the right result. I aim the meter at the light for edge or kicker lights, that are primarily behind the subject or to the side. With the meter at the subject, aimed back to the camera, it will not pick up any light, (the light will hit the back of the meter), so you really have no choice but to aim it at the light. TBH, I rarely meter these lights though as I've found over the years that I rarely end up using that value.
Ahh, you've changed your mind then, fair enough.
You're right that it's correct to meter to a backlighting light, but as you say that's pointless anyway, because the "correct" exposure is always the one that produces the required effect, not the technically correct one.
 
They work fine, but when you get to my advanced age you'll realise that life is too short to sod about with clothes pegs, and that masking tape was (or should have been) invented to do the same job in a fraction of the time, and without ever having to cut a sheet of gel :)

TBH, in the middle of a shoot, I'm not even gonna be picky about the type of tape - whatever I see first is what goes on the gel :/ I do still have my inverted clothes pegs somewhere, but I never use them these days.
 
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