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aczyzyk

Strobe temperature - cold or warm

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

Edited by davichin

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(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!

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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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: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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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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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.

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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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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.

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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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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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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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