sun exposure blues

Hello All

Well I have at last entered the digital age underwater with my S2 in an aquatica housing and a 16mm behind a standard 8" dome. No macro this go around because I quickly realized that digital wide angle was a bit more difficult than shooting with film. The initial results using the same manual settings I would with a Nikonos produced poor results, subsequent dives using different settings soon pruduced much better results.

All of the images, which include the sun in the background or just outside the frame result in the blue background turning quite green in the brighter portions of the shots regardless of aperture and shutter speed. Of course, faster shutter speeds/smaller apertures which resulted in darker backgrounds reduced the affect but did not eliminate it.

I have included a shot, bwhich was shot in RAW mode, the image had no adjustments in the conversion. nor any additional correction outside the conversion process.

I hope to get some tips as to how to correct the color either in the RAW conversion itself or in photoshop.

As for the Aquatica housing, I am quite pleased with it but there are a couple features that could use a bit of improvement.

The window for the top LCD could be a lot better/bigger, I had a VERY

difficult time seeing the info. Also it would have been nice if Aquatica

had printed the setting positions for the function dial on the housing. I will put a magic marker and

white-out to use, to correct this!

The tiny viewfinder on the S2 makes seeing the

info in the viewfinder a bit difficult.

Hard to work with a lo-res jpeg, but heres a quicky attempt:

Steps:

1. Image/Adjustments/Autocolor (did not help the water color, but improved the blue cast on the sea fan and diver)

2. Select/color range. Clicked on the area in question and fooled with fuzziness to select the area in question

3. Select/feather (to soften the edges of the selection so a hard boundary would not be shown between adjusted and unadjusted regions). Did not really matter at this size, but for a high res image for print, you need to be very careful about selective modifications

- stuff that doesn't even really show up on screen will be easily visible in the print to the discerning eye.

4. Image/adjustments/hue-saturation. Drag the hue slider to the right, making the selected area more blue and less green.

Here are some more heavy-duty modifications to show some of the stuff that can easily be done. It's a matter of taste and style as to whether these improve the image or not.

Duplicated the image to another layer. Used curves to brghten up the image a lot.

Added a layer mask, and used the gradient tool in the layer mask channel to

blend the brightened image with the normal one at the bottom of the frame. Basically moderating the bright to dark falloff a little bit.

Use clone stamp to remove the bubbles. Sometimes bubbles are nice but I wanted to show how easy it is to remove them if you don't want them for a particular image.

Use selective gaussian blur to smooth out the mach band in the gradient around the sun highlight. This band looked more like some sort of sensor phenomenon or posterization effect than the normal pleasing Snell's window effect. Probably this curved band is more pleasant in the full-sized picture when you can probably see water surface details, etc.

Dodged the lower part of the wall a little bit to make the strobe lit area blend more subtly into the non-strobe lit portion. Tried to bring a little color out in it as well.

Did 9% local contrast enhancement via unsharp mask with a large radius.

Added a salt water croc in the lower portion lunging to attack for a little more dramatic tension. Hit undo :-).

Chris,

Hi from DEMA. Blake and Norma from Aquatica say Hi.

I would suggest doing a lot of your color correction in the RAW converter as opposed to Photoshop.

Adjust the white balance using "Custom Setting"

Adjust the color temp to around 5000 for starters.

Pull the little "dot" around in the color space circle. Try pulling it to the upper right away from green and see what happens. Add to taste.

That should give you a natural looking blue water background and it will make your blacks look black, as opposed to black and green.

Cheers

James

WOW! Wetpixel RULES!!

Thanks so much for the rapid color correction tips. I have a lot to learn in regards to color correction. I am sure you will be seeing a lot more questions in the near future.

ChrisG, I can send you a higher quality image if you want to have a go at it. The help is more than welcome!

James, Give my regards to Blake and Norma, I am now on my 7th Aquatica housing. Compaired to the N90 and F5 housings, the S2 housing is by far the easiest to load the camera in. using the 16mm, two SB-104s and long TLC arms the rig is almost neutral (just slightly negative). I can balance it on my finger underwater!

Next time DEMA is held in New Orleans, I hope to be there as I can combine business and visiting family on the same trip.

Anyway, thanks again for the info

I will give these suggestions a go ASAP, but now I have to take some shots of a little girl in a Kimono (My real job!)!

Kindest Regards

Chris

I've noticed that the S2 produces greenish water in many of the tropical pics here on wetpixel. That is weird, because I hear people describe the colors as velvia-like, but velvia produces blue blues!

I never mentioned it because I didn't want to start a nik/fuji/canon debate!

The uncorrected Blues in images of the S2 do not come close to Velvia or even Provia but photoshop can take care of this. I am a bit disappointed in regards to the nasty Cyan cast it produces in the brighter areas of the tropical blue. The shot I posted was taken 30 meters deep and another taken at 60 meters still produced the Cyan cast.

Does the D100 produce better blues in and around the sunburst, than the S2? If so I may end up getting a D100 for my wide angle work. I plan to get a second system in the future so that I can shoot both wide angle and macro on the same dive. The S2 with it's TTl capability will then be dedicated to macro.

The S2 does do very well on land! The TTL works quite well.

Kindest Regards

Hang on a minute Chris. Before we declare the S2 a blue water loser, let's eliminate the other possibilities first.

Is your monitor calibrated? Did you convert the photo from RAW? If so, did you make it Adobe RGB, sRGB, or Fuji color space?

The green could (and probably is) coming from your conversion or white balance.

What about taking a sample of the blue water and seing what the RGB values are?

Cheers

James

I have no experience with canon or fuji to compare(except for images I've seen on the web), but I can say that I'm happy with the blue water that my d100 produces. Typically I shoot raw, but I usually don't need to deviate from the color balance that my raw converter (ACR) defaults to (based on the D100's suggestion). Here is a blue water image as it imports with no modification

With less brightness you can get even truer blues:

Looking at the individual RGB plates (as per James' suggestion) and examing the RGB values for different points in the blue can be quite useful.

Taking the original image, the lighter blue points in the upper part of the image have values in the general range of R:0 G:245 B: 243. In the lower darker portions, the water registers R:0 G:50 B: 105.

Not that the green value in the lighter upper part of the image is stronger than the blue value. That's not what you want for blue water.

ChrisQ's corrected image has values that are much more in line with what you would want (and what you would get shooting, say, Provia 100 under similar conditions - the light blues are now around R:0 G:171 R:255, while the dark portions comes in around R:0 G:65 B:161. Note that the flesh tones and color of the sea fan also fall into place as well, even on the "quickie" corrected version.

The original image is well within the range that can be easily corrected in Photoshop, as ChrisQ's adjusted image shows. It would be even better to get the values closer to what you want with the EX converter.

I think all of us who are using the F2 are working at finding the "right" EX settings to make these pictures work. I haven't come up with a set formula yet, but here are a couple of examples of shots I've taken with the S2.

In the first example, I think the blue is fine though the image isn't much. The original was considerably under-exposed, by the way, and brought back up in the EX converter by a stop or more.

In the second, I'm happy with the color balance for the main subject, but the green element in the lighter parts of the background water is too strong, but I wasn't able to correct without throwing off the colors in the main subject.

(What impressed me about this image was the blacks. In the full resolution image, the various different shades of black on Carlo's hood, BC, camera and gear are all very distinct. I was never able to get that kind of separation of different blacks when I was shooting film.)

I find when I am working the controls the D100 produces great blues when shooting horizontally. But as soon as I shoot upward at the sun I get a white sunball, a strong cyan halo and then blue water! None of the subtlety of film. So I still use film for these sorts of shots. I don't think that the S2 shots I have seen are signif different from D100 shots.

I find the cyan halo really nasty! Easily corrected in Photochop but still not wonderful.

Alex

Hi James

I am a Nikonos III film dinosaur and therefore a novice at software based color correction . I have very little experience futzing with images on the computer. Chris's tips helped a lot but I have so much more to learn.

My monitor is calibrated using a colorvision spyder and the prints pretty much match the monitor. Regarding the conversion from RAW, I have very little experience with doing this and hopefully I am at fault and not the S2. I used your suggestions which helped render a better overall blue background but it did not do much in terms of removing the cyan in the lighter areas. Using Chris's photoshop tips I managed to produce acceptable results but I need a lot of practice in order to produce a image that looks as if it has not been edited. Still I would like to avoid spending so much time on the computer to produce a image that looks like what I see in the viewfinder.,Hopefully someone on Wetpixel will find and share some general correction settings that can be used in the RAW conversion process.

I have not given up on the S2, I just need a lot of advice in regards to the "processing" of the images.

Teach me, ole wise ones of Wetpixel!

Until I get a handle on this, like Alex, I will still use film for these type of images

Chris

James

In regard to the colorspace in the RAW conversion, what do you recomend? I do not remember seeing the option but I will give it another go and see what I get.

What suggestions do you have regarding White Balance?

Chris

I don't think it is going to be possible to correct the water color in the raw converter.

The problem seems to be one of color shift towards green in the bright areas, requiring area-selective color correction. The color corections in the raw converters (at least adobe raw) apply to the image as a whole.

Chris - if you put the raw file on a website somewhere, or email it as an attachment

to chrisg@lplizard.com, I could take a stab at trying to correct the high res image in a

way that doesn't look edited.

***Explanation***

What you are seeing here is inevitable on any digital camera as you over-expose. If you had underexposed a bit, the problem would have gone away. What happens is the blue sensor is getting saturated in the region in question. The blue can't get any bluer, but the green can, which causes a color shift. The fact that it saturated at 245 instead of 255 is because of the mapping from the cameras native space to (I guess) adobe rgb, or because of exposure corrections made during import.

The over-exposure indicators on the cameras usually only show if the pixel is over-exposed in a monochrome sense - they don't indicate if just the red,blue, or green component of the color value is overexposed.

This form of highlight blowout is more correctable than the general one, since you "know" what color the region is supposed to be.

Bam! What Chris(G) said!

Try underexposing by 2/3 or a full stop Chris when shooting into the sun. You're on Guam, so I expect you to go jump in right now and try it...:-)

Then bring your RAW file into RAW converter EX Version 2.0.

1) It will popup a box and click on Adobe RGB 1998 Colorspace.

2) Next, check all the boxes for "Custom" so that you can adjust everything (if you want). Go down to "Sensitivity" which is Fuji's inept way of saying "exposure" and dial in 2/3 to a stop of compensation. Whatever looks good to you.

3) Then set your custom white balance. Either use the eyedropper to click on something that looks 18% gray or set it using the Kelvin slider. I usually start around 5,500K.

4) Then go into the color balance circle and drag the dot over away from the green (toward the upper right). I usually start w/ about 20 color units of green removal.

Then see what you have. You might have to switch steps 2 and 4, I can't say w/o having the program in front of me.

Chris is right that your sensor has "filled up" with blue. You need to bring all of the R, G, and B values down in order for you to have some latitude for your adjustments.

Cheers

James

Sorry for the Delay

I was in transit. Now back in Icy Japan Boo Hoo!!!

on my first 2 dives I did take some rather underexposed shots in the exact same location, but these were in JPG (fine) mode as I was trying to get comfortable with the housing and the various settings, therefore shot as many images as possible.

I will dig up these original images and take a peek. Hope to find a solution to this before I go back in November.

Yesterday in Tokyo, I checked for ND filters for the 16 mm, no luck! anyone know where I can get such a thing, or give me some advice as how to use gels with the 16 mm in my housing. I have never used gels and have no clue!

Thanks again for all the assistance!

Chris