Custom WB for a fishtank shot?

[Shultz]

Hi, please bear with me as I try to explain this as I'm a newbie to the world of DLSR

I want to use a custom WB setting for shots of my marine fish tank as the auto setting leaves me with to much work in the raw convertor to try & get the picture to "look" like what I can actually see

My first question is will the camera register a high WB as the metal halides above my tank have 20,000k bulbs in them?

Secondly using an old white lid to get the custom WB shot what angle should that be to the lights? ie the lights shine down from above & shots are taken from the front... So should the lid be looking straight out from inside the tank at the camera, or 45degrees looking up at the lights, or should I be trying to get the shot from above looking down at the white lid from between the lights?

Finally(!) once i have said shot I can see how to tell the camera which shot to use, but does it then need to stay on the memory card & does the camera know the setting & keeps it in until I change it?

Many thanks for bearing with me to read all of this, I hope it makes sense what I am trying to do?

Cheers Shelton.

[Shultz]

Nobody help me? Or have I posted this in the wrong section?

Cheers Shelton.

[Jon]

In reverse order, once you've set CWB, you don't need to keep the original. Those settings will be remembered until you select another picture for CWB.
Your camera should be aimed at the target from where you'd be taking the final pictures from. The target should be getting the same primary light that your subjects are. If the fish are getting only top light, then an angled target would be in order. If there's much front lighting, then a vertical orientation would be better.

The highest direck WB temperature the 20D at least supports is 10,000K. Are you sure your halogens are 20,000K? Although since colour corrections get smaller as temperatures get higher, that may not be too much problem. And Custom WB rather than dialling in a temperature may handle that ok.

[jfrancho]

Many halogen manufacturers clain 20,000 K bulbs. The truth of this is in great question. A friend of mine distributes CF lighting for the aquarium industry, and has measured the light temperature of several bulbs, halogen, VHO flo., Compact flo, etc. If I recall, the highest reading he got was something closer to 8500 K. I've also read that the 20,000K rating is a "simulated" rating, or marketing claim. Meaning that it has a lot of blue in it's spectrum, and advertised as such. Anyway, what Jon recommended should do the trick. Maybe one more thing that will work: keep the image you used to set the CWB, and if it isn't quite right from the camera, set it in ACR, and save the settings to apply to all the other images. Sort of the same thing, I guess. At least you are in RAW and can make the changes you need to. Back in the day I used to take color slides of fish in a special photograph tank, where many of the variables were under control. We still did plenty of bracketing due to the reflective/irridescent nature of the fish's scales. Good luck, and post what you get!

[Shultz]

Thankyou both for the help, I had been experimenting & think I need to try a 45degree one to get what I want, I have posted a couple of macro shots in said forum of a mushroom coral & Zoanthids in my tank, would love any comments/thoughts as to improvement though?

Cheers Shelton.

[jimsolt]

Originally Posted by Shultz

Hi, please bear with me as I try to explain this as I'm a newbie to the world of DLSR

I want to use a custom WB setting for shots of my marine fish tank as the auto setting leaves me with to much work in the raw convertor to try & get the picture to "look" like what I can actually see

My first question is will the camera register a high WB as the metal halides above my tank have 20,000k bulbs in them?

Secondly using an old white lid to get the custom WB shot what angle should that be to the lights? ie the lights shine down from above & shots are taken from the front... So should the lid be looking straight out from inside the tank at the camera, or 45degrees looking up at the lights, or should I be trying to get the shot from above looking down at the white lid from between the lights?

Finally(!) once i have said shot I can see how to tell the camera which shot to use, but does it then need to stay on the memory card & does the camera know the setting & keeps it in until I change it?

Many thanks for bearing with me to read all of this, I hope it makes sense what I am trying to do?

Cheers Shelton.

You have gotten some sensible advice here. Don't be distracted by whether the bulbs are putting out 20,000K or 19,478K. Remember your stated goal is to have the photo look like what you are seeing. I might suggest a white or gray surface slightly more sophisticated than the lid. Reflectivity will play a role.
If you want to try shooting RAW it might make your life easier. At any point in your sequence of shots hold a white or 18% gray card in the scene, shoot a picture and move on. When you process the RAW files, select the shot with the reference card in it, use your white eye dropper to identify it as white, and you will have the correct white balance for all shots in that sequence using that lighting.
I feel this method makes sense. Others feel that the RAW conversion becomes too much work.
If you're coming from film to digital, white balance serves the same purpose as filters, gels, and film types did. There's nothing mystical about it.
Jim

[Shultz]

What else could I use rather than a lid thats water proof, do you happen to know if something is made as 18% grey thats waterproof enough to be put in my tank for a few mins?

I do shot in raw all the time as its easier to correct mistakes I'm making! Tbh never used a film camera Had 3 or 4 point n' shoot digitals & this is my first SLR of any kind....

I agree about the bulbs, I know its only stated 20k, I just wondered if the camera could register higher than the 10k in the manual?

PLease keep the thoughts coming as this is all very useful for my fairly steep learning curve

Cheers Shelton.

[jfrancho]

I thought a little more about this. Assuming the lighting consistantly spreads throughout the aquarium, then the only variables in light temp (WB) would be hot spots caused by the bulbs, or water depth. I am going to take a guess that the metal halide bulbs are mounted horizontally, within a reflector/heat exchanger, that would eliminate the hotspot issue. I also assume that since you are using the "mega cool 20,000 K" bulbs that you do not have any auxillary lighting that would skew the consistancy (i.e. a couple of actinic 03 flo tubes to augment the daylight bulbs). If you do, leave them off for pictures, calibrating CWB. If all this is true, and the tank is less than 3 feet deep (water fulters light), we can reasonably take a CWB shot using anything thing white, waterproof, and inert (don't want to hurt your pets). I'm not sure that angle is going to matter, just solong that the object reflects light from the intended source, and fills the center of the frame for a proper CWB shot. One last thing: make sure you let the matel halides warm up for at least 90 minutes before shooting. These bulbs take a while to warm up, and their color temp changes dramatically during the process. I would recalibrate the CWB for each shoot. metal halides color temp changes over time, but only slightly, so better to be safe. And, like you said, you are shooting in raw, so you can fiddle a little if need be.

[Shultz]

Thanks, I do have atinics as well as believe it or not the 20k bulbs are not that blue looking! you think I should turn them off for daytime shots?

My lights come on at 11am, so I'll wait until this afternoon I try a few different shots with & without the atinics & also angled or not & see what difference (if any) it makes

Thanks once again, hopefully I'll have some good shots to post before long!

Cheers Shelton.

[jfrancho]

Originally Posted by Shultz

Thanks, I do have atinics as well as believe it or not the 20k bulbs are not that blue looking! you think I should turn them off for daytime shots?

My lights come on at 11am, so I'll wait until this afternoon I try a few different shots with & without the atinics & also angled or not & see what difference (if any) it makes

Thanks once again, hopefully I'll have some good shots to post before long!

Cheers Shelton.

Also, try it with the WB calibrated without the actinics, but shooting with them on. You might get some interesting effects. Can't wait to see the pics. Send a PM if you post and don't hear back from me.

[reewik]

I too have a saltwater set up... reef to be exact, what you got?

[MitchellB]

i shoot a lot of aquatic stuff. I use the high speed flash, a custom white balance with a coffee filter or just auto.

I shoot mainly wide open with a tameron 90mm.

My bulbs are radiums...20K and a pain

see some shots here under aquatic

www.ihigallery.com

[reewik]

Talk to me MitchellB...School me.. What is your setup... Really nice!
www.geocities.com/reewik

[Shultz]

Originally Posted by jfrancho

Also, try it with the WB calibrated without the actinics, but shooting with them on. You might get some interesting effects. Can't wait to see the pics. Send a PM if you post and don't hear back from me.

Hi, thanks for the advice, one of my dogs has been very ill so I haven't had a chance to to try things out Will be changing over to my new tank this weekend so hopefully have some new stuff to look at by this time next week

Originally Posted by reewik

I too have a saltwater set up... reef to be exact, what you got?

Just a small setup, now going slightly bigger reef in a 36x20x24 with sump, you got any pics to share?

Originally Posted by MitchellB

i shoot a lot of aquatic stuff. I use the high speed flash, a custom white balance with a coffee filter or just auto.

I shoot mainly wide open with a tameron 90mm.

My bulbs are radiums...20K and a pain

see some shots here under aquatic

www.ihigallery.com

Wow! thats just a truly stunning gallery..... Love the various Zoanithids you have, do you just have the 20k Radiums or Actinics as well as those colours are real popping & I'm thinking of changing my bulbs

Cheers Shelton.

[reewik]

Originally Posted by reewik

Talk to me MitchellB...School me.. What is your setup... Really nice!
www.geocities.com/reewik

Here are a couple shots but That is when the tank switch was new. I am in the process of getting some new shots. WB has also been my problem shooting the tank. I have 15,000k 's and actinic pc's. I see lots of blue from the light. This is where I wish I could set the WB by color temp like the 20D.

I also really want the 100mmm macro to add to me bag.