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Strobe temperature - cold or warm


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#21 james

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Posted 19 September 2006 - 12:34 PM

Whoa nelly Manual, when you say: "though I understand that being in some disagrement with you, on this forum, is not looked upon kindly" you are taking this from a technical discussion to a personal level.

Alex is well liked here on the forums, and this is due to his friendly nature and willingness to help others. Surely this is recognized by our members - but this doesn't extend to the level of our members blindly declaring that everything Alex says is right. Where's the fun in that?!?!? :-)

While many of us have posted in this thread corroborating information backing up the assertion in Alex's article, this is because we believe in the merits of the assertion - not just because of the author, but because of our own technical know-how and experience.

Please give us credit for that - we are not sheep. Anyone here is free to challenge what I SAY without challenging ME, and I believe Alex has always felt and stated the same thing. This has been a cornerstone value here at Wetpixel from the start.

Cheers
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#22 SilvioMarchena

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Posted 19 September 2006 - 01:09 PM

To get back to the original question. I can't show you the difference between using warm and cold strobes because I use warm strobes only. However for what it is worth, here are the advantages:

I use both 4800k and 5500k strobes, but cannot show a comparison because I do not have anything shot..same subject, same day, same conditions, once with each temp strobes on board. And without that benchmark it will be meaningless. But I can tell you that at those temps the differences are very very subtle. They are certainly real, but in reading these forums one would think there is this drastic cold blue image vs. this saturated red one, and that isn't quite the way it works out.

The words warm and cold each infer a natural and expected level of comfort, but you should not translate that to strobes. The "cool" strobe is one that is actually trying to replicate daylight on a sunny day (5,000 to 6,000k), nothing more. A "warm" strobe is one that infers a bit more red on on most images. In my view there is a time for each and circumstances in which the properties of each apply differently. And keep in mind that the temp of each is at full power without diffuser. Lower power settings and diffusers will lower temp. So while you can easily go down from the rated temp of a strobe, I do not believe you cannot go up.

I'll say this though----if I was to carry but one set of strobes they would be warmer ones.
Cheers,
Manaul


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#23 SilvioMarchena

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Posted 19 September 2006 - 02:07 PM

Whoa nelly Manual,

NO YOU DIDN'T!!!......no you didn't say "Whoa nelly"! :lol: James, that's way to funny :blush:

Listen, I am sincerely sorry if you thought I was calling you a sheep (I am generally far more crass than to call anyone a benevolent fuzzy animal). I must admit though, that it is a curious interpretation of what is an accurate comment (the e-mails I have received indicate that there are people who look unkindly on challenging Alex's assertions). To me there's no harm to this being the case and there is nothing cowardly about any forum having preferred commentators.
Cheers,
Manaul


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#24 aczyzyk

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Posted 19 September 2006 - 11:56 PM

Thanks for all inputs. I guess I understand it better now.
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#25 davichin

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Posted 20 September 2006 - 02:55 AM

The National UWphoto Contest in Spain took place two weeks ago.....AGAIN :blush: E.T. a.k.a. Carlos Minguell and Caty Perales took a first place (I don´t how many years now they have done it.... :lol: ) followed by a close second Marc Casanovas. It was held in Galicia, in the northwest of the country, where the atlantic waters are cold, hard and very green. Now, in relation with the topic, checkout the bluer blues of Marc taken with warm filters in his "cool" sea&sea strobes and WBalancing:


Posted Image


And this is how the water really was: (pic from the champion Carlos Minguell):using Inons


Posted Image


you can check the pics in Mariano Morell (mmb in wetpixel) website:


http://mardigital.ne...mp;limitstart=2
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#26 davichin

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Posted 20 September 2006 - 03:08 AM

one thing: both used D200 and no PS ( they had to use jpgs straight from the camera)

Edited by davichin, 20 September 2006 - 07:17 AM.

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#27 buddy

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Posted 21 September 2006 - 02:37 AM

(1) Quoted from james:
If you shoot a 4300K strobe and set your white balance to 4300, you will end up w/ a "properly" exposed foreground and a certain colored water.
If you shoot a 5500K strobe and set your white balance to 5500, you will end up w/ a "properly" exposed foreground and a certain differently colored water.
In the above two examples, the foreground subject will look EXACTLY THE SAME however the ambient exposure will be different.
So in essence, your choice of strobe is affecting your ambient/background exposure.

and (2) quoted herbko:
Just in case you're not confused by the above, if you choose a color temperature white balance setting for your camera or raw converter, increasing the temperature will make your photo look more red. That's because the camera or software assumes that your light source is at that color temperature and compensates to give the "true" color for the subject.
Higher color temperature source -> more blue in the light -> photo is shifted to the red to compensate.

Here comes my consideration:
if the above is true saying that basically the picture will differ for color temperature in the background area (opposed to the same foreground) by 2 strobes with different color temperature (as per quote 1)

AND

the higher the color temperature setting in your camera is (let's say by setting it to the higher strobe temp like 5500 K vs 4300K) vs the real color temperature which is actually in the water (especially in the background), the more reddish (warmer) your picture will be.

Example:

strobe 1 color temp = 4300K
strobe 2 color temp = 5500K
actual background color temp = 4000
camera setting 1 = 4300K
camera setting 2 = 5500

result: picture 2 will look warmer in the background than picture 1 (with the same foreground) since color setting in picture 2 is higher than in picture 1. However, both pictures will look slightly warmer than neutral in the background, since the assumed actual color temp is lower (4000) than both settings (5500 and 4300).

That would leed us to the (premature) conclusion that finally strobe 2 (@5500) renders a warmer picture????

BUT, as I thought about, isn't it the case that the actual color temperature in the water (esp. in the background with no illumination from the strobe) is rather hiher than lower, saying like 6500K? In this case -my understanding- the 4300 setting following the 4300 strobe would produce a warmer picture in the background (since the camera will compensate more for the difference between 6500 and 4300 than for the difference between 6500 and 5500). Is this correct or confusing??? hope this post is not too long.... but if someone can confirm this, then I know that I finally got it!

Juerg
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#28 Paul Kay

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Posted 21 September 2006 - 07:07 AM

I don't think that you can think of the background in terms of colour temperature I'm afraid. Firstly the background water colour varies depending on where, when and what is influencing the water as well as the time of day, cloudiness, etc, etc. Secondly the water will generally only have blue and sometimes green components (except in the shallows) so describing it in terms of colour temperature is not really applicable.

It would be interesting to shoot the background and then see what colour temperature PS describes it as - but I expect that this will be accompanied by a significant tint adjustment too!

The point here is that white balancing the foreground illumination will have an effect on the background colour which is to some degree predictable. The warmer the strobe, the bluer the background may become if the foreground is white balanced and its red quotient reduced (together with some subtle reduction of other colours).
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#29 ce4jesus

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Posted 22 September 2006 - 11:58 AM

:blush: Stobe temperatures ;) Reds, blues, greens ;) warmer, cooler :blink: 5000K :blink: white balance :blink: :wacko:

...must buy what alex recommends....must buy today! :blush: Baaaa Baaaaa!

"Please give us credit for that - we are not sheep. Anyone here is free to challenge what I SAY without challenging ME, and I believe Alex has always felt and stated the same thing. This has been a cornerstone value here at Wetpixel from the start."

Are you saying you're a black sheep? :lol:
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#30 cdascher

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Posted 22 September 2006 - 09:35 PM

Since the topic is up, does anyone know of a maker for an UW color card or greybalance card? I want to start taking a test shot each dive for later WB calibration. I know some folks use the small UW "white" marker board.

Chris
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#31 mattdiver

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Posted 23 September 2006 - 02:42 AM

Since the topic is up, does anyone know of a maker for an UW color card or greybalance card? I want to start taking a test shot each dive for later WB calibration. I know some folks use the small UW "white" marker board.

Chris


For that particular purpose you can just buy any 18% grey card for land use, and laminate it.

Just make sure you leave plenty of space around the card when you laminate it, so that you can punch holes through the edges for clipping the card to your BCD.

#32 loftus

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Posted 23 September 2006 - 09:11 AM

I have seen underwater cards used by Stephen Frink, I beleive they had Jim Church's name on them. You may want to check with Stephen Frink or Kathy Churh in Cayman,
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#33 SilvioMarchena

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Posted 23 September 2006 - 04:07 PM

Is this correct or confusing??? hope this post is not too long.... but if someone can confirm this, then I know that I finally got it!

For RAW capture I think it is better to remember that WB setting in the camera has no effect at all on the pixel capture information. This way all you have to think about is that you are simply attempting to create a differential in foreground and background temp that allows you to cool/warm the whole image in a way that brings foreground and background to a point where both are pleasing to your eye. But in all cases getting the same exact blue background is as easy with one strobe temp as it is with the other, if you consider that a person's foreground temp is a matter of personal preference.
Cheers,
Manaul


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#34 Poliwog

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Posted 23 September 2006 - 06:39 PM

Since the topic is up, does anyone know of a maker for an UW color card or greybalance card?


I use a “Digital Gray Card” marketed by Robin Meyers Imaging.

Their website is located at: http://rmimaging.com/

The card I use is located on this webpage: Gray Card Webpage
This gray card is made of a plastic material that is waterproof and has the pigment impregnated all the way through the plastic base. The card comes in two sizes, the 4x6 inch size being the one I use underwater (both salt and fresh waters). You can sand any nicks and gouges out of it and not affect the colour of the gray card. The price is nice too -- just $14.95 U.S.

I drilled a ¼ inch hole in one of the corners of it and attached it to a retractable lanyard on my BC. Works great, although it is a little difficult to get a good white balance with it when using a 10.5mm wide angle lens.

For anyone residing in Canada and wishing to purchase one, you can order one (or two as I did) through “Headshots” located in Toronto. Their webpage is located here: Headshots Rentals

I’m not affiliated with “Robin Meyers Imaging” or “Headshots Rentals” – I’m just a happy customer and pleased with the gray card. :blush:
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#35 meister

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Posted 23 September 2006 - 09:18 PM

I bought one of these. I haven't got around to working with it yet, but will next week.
http://www.rawworkfl...ibal/index.html
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#36 John Bantin

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Posted 24 September 2006 - 09:35 AM

Aesthetics and semantics! What a combination!
It seems to me that none of this really matters as long as you like the result. I would note that since we humans prefer sunny days to overcast weather, and we are quite happy to spend hours under low-colour-temperature tungsten lighting, we tend to be more comfortable with a warmer result. So when shooting with the Mega Color that gives an option of colour temperatures to its output, I invariably go for the warmest setting.
Of course the flash does not affect background lighting colour temperature but the overall colour temperature setting of the digital process does!
The funny thing is that underwater, you can get away with murder. It's only flesh tones or the reproduction of a specific colour (as in a packshot) that reveals how badly we can get it wrong. My new catch-phrase? It's art, not reality!

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#37 Rattus

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Posted 27 September 2006 - 02:18 AM

Another way of looking at the relative merits of different colour temp strobes is in terms of colour contrast.

To make a striking image it is often preferable to differentiate the subject from its background using colour contrast between the two. One way to do this is to render the blue water background as black, so that only the subject has any colour at all.

When the blue water background is rendered as blue, the warmer the strobe colour (lower temp in Kelvin) the greater the colour contrast will be. This contrast is largely unaffected by choice of white balance, though most people will set the white balance to the temperature of the strobe, either at time of capture, or later at the RAW conversion stage or during similar post processing for those using JPG.

Having spent last week in Cayman trying to maximise this colour contrast, it seems a good way to approach the issue of strobe temps.

Martyn
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