I have questions regarding the selection of the color temperature of a flashlight, especially to people who change the temperature, depending on conditions:

 

My understanding is that for photos that are lit (almost) exclusively by a flash, e.g. macro, color temperature of the flash is unimportant as the temperature of the raw file can be adjusted delibertately in postprocessing, e.g. LRc...

 

The color temperature of a flash becomes important, when ambient light and artificial light from a flash get mixed. e.g. WA. The warmer the color temperature, the less adjustment of the raw file is required in order to get the correct WB for the foreground subject that is lit by the flash. Hence, the background color, e.g. open water, is less influenced by the WB procedure and the blue will be more natural...

 

 

 

Here is an example photo that I produced on my last trip to the Carribean, using two Inon Z330s with standard diffusers. The color temperature of these flashes is at 5500K. WB was adjusted to show the correct colors of the reef shark (Carcharhinus perezi) to the left in the foreground:

Sony A7R5, Sony 20-70mm @20mm, 1/160s, f/9, ISO 400, 2*Z330:

 

I guess, if I would have used diffusers to warm up the color temperature to 4500K I would have a "better" blue in the background, i.e. less "greenish" cast?

 

 

How do you adjust the color temperature of your flashes and what temperature is the optimum for what conditions?

 

 

 

Thanks, Wolfgang

 

Edited May 6, 20241 yr by Architeuthis

Warmer temperature of your strobe means the blue gets more saturated

it is not about the tint but about the color temperature

 

I have tried all sorts of filters 4600 4900 5500 ambient light and today I find my Sea and Sea YS-D2J 5250 just perfect and would not go any different

This is because you can use masks to get the blue you want if there is an issue with it

 

Some strobes have natively a look that is nicer than others, the key is to get the natural color without having to play with diffusers or filters

I use INON Z-240s and have generally used the 4600K diffusers that came with the units in tropical blue waters and I've been happy with the results.    I have not done extensive comparisons using different diffusers though.  Agree it's about colour temperature balance, not tint.  If you are using INON strobes, diffusers I think are a given whether they are the standard ones or the warming diffusers.

For myself I would rather get it right in camera, there are various ways of addressing the blues without impacting upon the main subject including masks, but If I can get away without drawing masks on my images I will, depending on subject they can be fiddly and you always risk edge effects around your subject.

Color temperature of a strobe is an interesting topic.

 

Basically, a warmer color temperature of the strobe light will give you a nicer color of the blue water in wide-angle shots. The automatic white balance tries to contain an average of I think 18-19% grey. If you hit the foreground with a warmer light color from the strobe, the white balance in camera "counters" this with getting the whole image a cooler color, giving a better blue right out of the cam. The effect does mostly show if a good portion of the image is lit with the strobe (affecting the white balance of the whole image), so you can see it more in reef scenes or something like that.  

 

I think it can be achieved in postproduction, but it can sometimes be difficult. I found the colors look best if you get it right in camera, without having to change the hue and saturation of the blue in the RAW converter. But that is only my experience. 

A warm color temperature is one element of a good quality of light on a strobe (but not the only one). And if you ever have used a strobe with a really good quality of light (Seacam, Retra) you will instantly see the difference to other strobes... it really can transform wide-angle pictures! And you might never want to go back 😉 

The quality of light is the key feature of a strobe in my opinion and I am often astonished how people will discuss recycle time and guide numbers, just to eventually end up with unpleasant light (been there, done that 😉 ). 

 

If you have different diffusors, I would for wideangle always go for the warmer color temperature. For freshwater, this can be different, as you want to get a pleasant green water color and not blue. But I don't dive in fresh water and have therefore no experience in what color temperature ist best for freshwater. 

 

In this particular image in the first post the effect of a warmer strobe or diffusor might not have altered the background color too much, as only a small portion of the picture is lit with flash.

I am amazed by the fact that shooters discuss this in depth who use Lightroom at the same time!

 

.. noting the fact that bloody LR will reset and flatten your raw files upon import and you have to work yourself backwards on to get what you saw on your cameras LCD underwater.

 

Strobe Color Temperature is highly overrated as it will just apply to 

- white balance = AUTO
- file format = JPEG

shooters who want to be done when they exit the water.

 

The following will therefore just apply to a certain type of underwater photographer:

- green water = cooler strobe temp 

- blue water = warmer strobe temp

is slightly beneficial for rendering better blue or green background in AUTO WB.

 

The logic and scientific approach is much different:

1.) buy the strobe with the coolest color temp 

2.) manual white balance onto that strobes color temp or set the camera to a fixed Kelvin Value of your choice, measurement

 

why?

- get the same or even better effect as with AUTO WB

- utilize the fact that you are bringing optimized photon energy into the water

 

Kelvin Values can be viewed as the integral under a nanometer color spectrum curve measured.

 

The warmer your light strobe, the more absorption you will suffer from in water. With increasing distance the warm light is the first to get absorbed. Basically you are wasting a lot of energy and battery power trying to don quichotte the water column.

 

Keep in mind that this is not true for very close macro distances, where high CRI and low Kelvin values are considered to be beneficial.

In all the years I’ve been doing underwater photography, I don’t think I’ve ever given thought to the colour temperature of my strobes: Nikonos, then Inons and now Retras. 
 

I’m not sure what that says about me or my images! 

1 hour ago, Adventurer said:

I am amazed by the fact that shooters discuss this in depth who use Lightroom at the same time!

 

.. noting the fact that bloody LR will reset and flatten your raw files upon import and you have to work yourself backwards on to get what you saw on your cameras LCD underwater.

 

Strobe Color Temperature is highly overrated as it will just apply to 

- white balance = AUTO
- file format = JPEG

shooters who want to be done when they exit the water.

 

 

This is not the reason people wish to use warmer strobes.  The reasoning is that a warm strobe when white balanced back to daylight colour balance will render the water bluer.  The water is not illuminated by the strobe so it has no impact on the water directly.   You can't get this effect by just white balancing cooler as the subject will then be too blue.   It's the same problem you get for example shooting flash of for example a sunset with with a flash lit foreground subject.  The WB will only be "right" for one subject as you are mixing 5000K flash light with 2000K sunset light.   The WB can only be "right"for one - not both.

 

Not sure if all cameras do this but as I understand it at least some set the WB to standard colour temperature for flash assuming it will match and produce pleasing skin tones.  So Auto WB when shooting flash defaults to 5000K or whtever the manufacturer uses.

 

Tend to agree on LR, I don't use it but as I understand it  you can set it up to use your WB and other settings as a preset to give you a starting point.

First, let me thank all of you for the interesting comments...👍

 

Until now I was using my strobes (Z-330) at color tempearture as they come from the factory (5500 K). Two weeks ago,  I pre-ordered two Backscatter HF-1 strobes with different types of diffusers (6500 K, 5500 K and 4500 K) and am glad to read how people use such filters (or some, not at all), to have a first orientation for my own experimentation...

(I, personally, am convinced that it is better to adjust the color temperature relation between artificial and ambient light already before the light hits the sensor (this was the reason for per-ordering two HF-1's plus filters). There will be always corrections in post-processing, also using masks, but the smaller such manipulations are, the better the final outcome will be (this is at least my hope))...😊

 

 

Wolfgang

Edited May 13, 20241 yr by Architeuthis

I fully agree on trying to get the best colors out of the camera.

 

I learned from AM in a REBOOT course that 5500 K result in the nicest greens in less transparant waters, while 4400K result in the best blues. So now I use my Z-330 strobes with or without 'SOFT' diffusers in green waters and  use the 4600 K diffusers in blue waters. With pleasing results.

59 minutes ago, Floris Bennema said:

I fully agree on trying to get the best colors out of the camera.

 

I learned from AM in a REBOOT course that 5500 K result in the nicest greens in less transparant waters, while 4400K result in the best blues. So now I use my Z-330 strobes with or without 'SOFT' diffusers in green waters and  use the 4600 K diffusers in blue waters. With pleasing results.

I too use the warmer diffusers in blue water.  Do you also set your camera to 4600, auto, or other?

On 5/13/2024 at 6:45 PM, Architeuthis said:

(I, personally, am convinced that it is better to adjust the color temperature relation between artificial and ambient light already before the light hits the sensor (this was the reason for per-ordering two HF-1's plus filters). There will be always corrections in post-processing, also using masks, but the smaller such manipulations are, the better the final outcome will be (this is at least my hope))...😊

If you want to go that way and be just super precise and optimized try the following: photo and strobe (white or grey) sand in your desired subject distance and use that white balance reference picture to set the manual wb. This will take the water effect on that particular dive,  strobe color temp and diffusers into account. 
 

The manual Wb on most cams will include more parameters than just the Kelvin value. 
 

I personally would not use the diffussors then unless I have to increase beam angle or want more soft light instead of hard light.

Edited June 4, 20241 yr by Adventurer

49 minutes ago, Adventurer said:

If you want to go that way and be just super precise and optimized try the following: photo and strobe (white or grey) sand in your desired subject distance and use that white balance reference picture to set the manual wb. This will take the water effect on that particular dive,  strobe color temp and diffusers into account. 
 

The manual Wb on most cams will include more parameters than just the Kelvin value. 
 

I personally would not use the diffussors then unless I have to increase beam angle or want more soft light instead of hard light.

 

I photograph in RAW and therefore I can shift the color temperature of the water to any value I want in post at high quality. I set the WB on the camera to "Auto" or to a preset value (e.g. color temperature of the flash), but this is just for viewing immediately in the viewfinder, or as a first suggestion after import in LRc. WB during making the photos is not very important for the way I make photos (with video this is, of course, a different story)...

 

The trick with different color temperature(s) of the flash is that the temperature of ambient light is given, but one can adjust the temperature of the artificial flashlight with filters: hence the ratio in temperature of ambient/artificial can be adjusted by choosing different filters...

=> As some suggest above this ratio can be also adjusted by selectively adjusting temperature using masks (this is how I do it at present, by the way), but these masks are never perfect and sometimes artifacts become apparent.

 

 

Wolfgang

9 hours ago, Floris Bennema said:

I fully agree on trying to get the best colors out of the camera.

 

I learned from AM in a REBOOT course that 5500 K result in the nicest greens in less transparant waters, while 4400K result in the best blues. So now I use my Z-330 strobes with or without 'SOFT' diffusers in green waters and  use the 4600 K diffusers in blue waters. With pleasing results.

Back in the days Alex pushed Inon to develop the various strobe diffusers

I have those with my Z240 and i have experimented extensively

Firstly the results change depending on where you go because the water is not the same around the world, second I had some really bad results with certain combination of cameras with the 4600K diffuser for example that resulted in excessive cast

Ultimately it boils down to individual preference my preference if for something around 5200-5500 K indeed not excessively warm

And finally xenon tubes are 5000-6000K not less so anybody saying you can deliver 4900 straight out of the box is either having something built in on the strobe front or this is simply an optimistic view

It doesn't look like you can assume you are getting the colour the diffuser claims when you take a picture underwater...

 

Re Inon diffusers... From Driefish "The S-220 for example measure as 6650k without diffusers and 5400k with the Inon '4600k' filter."

 

I am intrigued why the manufacturers may be off. Is there a reason or is it, say, the way the measurement is taken in water? I don't see any marketing logic for a manufacturer to incorrectly state a diffuser colour. The may not want their strobe to appear to customers as too high Kelvin, and that may be a trade-off for power, but if they make a range of diffusers why not be accurate?

31 minutes ago, John E said:

It doesn't look like you can assume you are getting the colour the diffuser claims when you take a picture underwater...

 

Re Inon diffusers... From Driefish "The S-220 for example measure as 6650k without diffusers and 5400k with the Inon '4600k' filter."

 

I am intrigued why the manufacturers may be off. Is there a reason or is it, say, the way the measurement is taken in water? I don't see any marketing logic for a manufacturer to incorrectly state a diffuser colour. The may not want their strobe to appear to customers as too high Kelvin, and that may be a trade-off for power, but if they make a range of diffusers why not be accurate?

Backscatter measures (on land) are also different from the specs (to the point it makes me wonder about their method)

 

Retra is 5800 not 4900K

Sea and Sea 6600 not 5800K

 

Color temperature should be measured on land not in water and should report temperature and tint

 

The latter is not published but it is what creates cast in your images

 

How do I measure color temperature of a strobe? I take a picture of a person on land and compare to my topside flash

nothing scientific but I can see if there is a cast or else

 

 

 

 

10 hours ago, Interceptor121 said:

And finally xenon tubes are 5000-6000K not less so anybody saying you can deliver 4900 straight out of the box is either having something built in on the strobe front or this is simply an optimistic view

At least the Seacams seem to have some kind of yellowish color on the flash tube, maybe some kind of coating/treatment. They are rated with 4400k. As they provide the GN for underwater, that might be true for the color temperature too. In the Retra comparison you can clearly see that they have a warmer color temperature. Their diffusor does not alter the color temperature, it is just a white diffusor.

50 minutes ago, ChrisH said:

At least the Seacams seem to have some kind of yellowish color on the flash tube, maybe some kind of coating/treatment. They are rated with 4400k. As they provide the GN for underwater, that might be true for the color temperature too. In the Retra comparison you can clearly see that they have a warmer color temperature. Their diffusor does not alter the color temperature, it is just a white diffusor.

It will always be in air

Xenon get cooler as power goes up

perhaps color temperature is measured at low power 

if the reflector has a color it would be the way to make the strobe warmer for example

Edited June 4, 20241 yr by Interceptor121

22 hours ago, ChipBPhoto said:

I too use the warmer diffusers in blue water.  Do you also set your camera to 4600, auto, or other?

I always leave it to auto. According to ChrisH explanation that does the trick. 

1 hour ago, Floris Bennema said:

I always leave it to auto. According to ChrisH explanation that does the trick. 

I tend to do the same, or set at “daylight” if in bright blue water.

Thanks!

16 hours ago, Interceptor121 said:

Backscatter measures (on land) are also different from the specs (to the point it makes me wonder about their method)

 

Retra is 5800 not 4900K

Sea and Sea 6600 not 5800K

 

Color temperature should be measured on land not in water and should report temperature and tint

 

The latter is not published but it is what creates cast in your images

 

How do I measure color temperature of a strobe? I take a picture of a person on land and compare to my topside flash

nothing scientific but I can see if there is a cast or else

 

 

 

 

 

Backscatter tests it using a Sekonic spectrometer. I've tested it both with a Sekonic and by shooting an 18% grey card in macro conditions ON LAND (F32, ISO100, 1/250 to limit ambient light) and then checked with the WB tool in lightroom. The results of these methods match closely (within 100-200 degrees Kelvin).  Testing color temperature should be done on land as backscatter does it because any amount of water will introduce filtration, and the specific amount of filtration will depend on the number of particulates in the water and the distance. Air has much less of a filtration effect at close distances. 

 

Incidentily, my results also generally match the Backscatter results. I measured the Ikelite DS230 at 5200k (via 18% grey card method) and Backscatter got 5400k. (Advertised specs are 5000k). 

 

Of all the strobes I've tested myself or that Backscatter has tested, the Ikelite DS230s were the closest to the manufacturer's specs. Everything else is anywhere from 500-1000k cooler.

 

Why is it? Probably.. marketing. As Massimo explained, Zenon flash tubes produce somewhere between 5000-6000k natively. To get it warmer, you have to apply a warming coating to the flash tube, which is what Seacam/OneUW and probably Retra / Ikelite do. This of course absorbs some part of the spectrum of light, leading to lower overall light output. You can check this out by having a close look at the flash tubes on your strobe -- do they have a orange-yellow tint or coating?

 

What I'm curious about is whether this method of coating the flash tube degrades over time and leads to strobes becoming cooler as they get older. That would be a big downside vs alternative methods of warming up the strobe temperature like click-on filters. 

 

 

I've measured strobe color temperature always on land, because water introduces an unknown filtration variable. I've used two methods -- a Sekonic spectrometer (which is what Backscatter also uses) and taking shots of an 18% grey card illuminated with the strobe using a macro lens at F32 ISO 100 1/250th to minimize impact of ambient light. With the grey card method, I then use the WB tool in Lightroom on the grey card (shoot in RAW) to see what color temperature Lightroom reads to render neutral grey. 

 

Both these methods produce quite similar results, within a couple of hundred degrees kelvin. For example, the Marelux Apollo 3s without diffusers measure as 6500k with grey card method or 6800k with Sekonic spectrometer.  With the diffusers, grey card gives 5800k and Sekonic 6000k. So I'd say you get to within 200k margin of error with either method.

 

My results also tend to closely match Backscatter's, which also uses a Sekonic spectrometer. . For example, I've measured the Ikelite DS230s as 5200k with grey card method. Backscatter got 5400k with spectrometer. This strobe, by the way, comes closest to the advertised specs of 5000k. 

 

Every other strobe I've tested is somewhere between 500k-1000k cooler than advertised. Why is that? All I can conclude is.. marketing. Manufacturers know that warming up a strobe means inevitably decreasing the power, and they'd rather have higher GNs. Power is fairly easy for a user to 'see' and complain about. Color temperature.. not so much unless you're a nerd and into testing these things.

 

As Massimo says, zenon flash tubes have a native color temperature between 5000k-6000k. So to get a warmer strobe, what manufacturers like Seacam/OneUW and perhaps Retra and Ikelite do is apply a orange-yellow coating directly to the flash tube. If you have one of these strobes, check the flash tube -- does it seem a bit yellow-orange? Others like Inon and Backscatter offer optional snap-on filters that accomplish the same.

 

I wonder if the coating method actually wears down over time as the strobes fire and age. This would lead to color temperature becoming cooler over time with no way to fix it? That'd be very bad.  Perhaps the click-on filters are a better method.  

10 hours ago, Interceptor121 said:

It will always be in air

Xenon get cooler as power goes up

perhaps color temperature is measured at low power 

if the reflector has a color it would be the way to make the strobe warmer for example

This. I tested the OneUW extensively with the Sekonic specrometer. -- they're the OEM for Seacam strobes as well, as far as I know. Interestingly, there is a big jump to warmer color temperature around -4 stops. If the Seacams behave the same way.. I find this rather deceptive and frustrating in use as well. 

 

13 minutes ago, DreiFish said:

This. I tested the OneUW extensively with the Sekonic specrometer. -- they're the OEM for Seacam strobes as well, as far as I know. Interestingly, there is a big jump to warmer color temperature around -4 stops. If the Seacams behave the same way.. I find this rather deceptive and frustrating in use as well. 

 

It is the physics of xenon tubes higher energy particles are cooler

this is also rather interesting because it means that you need more power so you have margin to get warmer color and when you shoot at full power the light will already be cooler which we all experience in big school scenes

 

20 hours ago, John E said:

Inon diffusers... From Driefish "The S-220 for example measure as 6650k without diffusers and 5400k with the Inon '4600k' filter."

 

I am intrigued why the manufacturers may be off.

Well, don‘t be too harsh with the manufacturers.
 

First, we do know if @DreiFish Spectrometer has been regularly and properly calibrated. Second, has it been done in a completely dark room ( I mean pitch black room ) or outside or living room environment?

 

The ambient light might heavily distort the spectrometers readings. 
 

If you want to be precise you need to take it into an Ulbricht Sphere.

 

However I highly appreciate Dreifish‘s home probing. Maybe he can let us more about his test environment? Furthermore I suggest to do multiple measurements for each unit to get an idea about measurement variance and errors.

2 hours ago, DreiFish said:

Every other strobe I've tested is somewhere between 500k-1000k cooler than advertised. Why is that?

Xenon Strobe tubes and LEDs have a manufacturing variance and tolerance in that range. More closely to the 500k instead of 1000k though. So that offset may come from the component source.

 

Furthermore ambient light might have cooled down your measurement.

 

And as Massimo pointed out correctly full power measurement is cooler than in mid range color temp measurement. This would support your marketing accusation a little bit, if strobe manufacturers did not measure color temp at full output. The latter one however is a very practical approach as most of the users don’t fire at FULL all the time.

 

@DreiFish the Marelux MTL reading freaks me out?!? I cannot really get my head around why a lower strobe power should be the coolest of all 🙏😇 Maybe you guys can up with ideas for this? 

Edited June 5, 20241 yr by Adventurer
Added marelux MTL reading question.