Jump to content
UltravioletPhotography

Pushing WB to Shoot in Nikon Red


Andrea B.

Recommended Posts

EDIT: I amended the title from Shoot in Nikon's Red Channel to Shoot in Nikon Red.

EDIT:  I amended the title from Shoot in Nikon Red to Pushing WB to Shoot in Nikon Red.

 

I'm pretty sure you can perform the following trickery on other digicams, but I haven't tried it just yet on my A7R or GH1 or K5.

 

 

This is ----->>>>>> How to Shoot a Very Red Photo with a Nikon DSLR

 

Fill a monitor screen with a Cyan Tif against which you will make a white balance preset. Because you are using a Nikon (for me, D500 today) all of which are known to be rather snarky about white balancing against anything non-grey, do not use a high saturation Cyan. I picked a (153, 255, 255) which was 40% saturated and it worked OK.

 

So, make a typical white balance preset against the Cyan screen.

Shoot a well-exposed photo of anything. It will be fairly Red looking.

Pull the card and read the mltuipliers for the photo you just took.

4.69, 1.00 .91, 0.00 (read with dcraw and rounded to 2 places)

See the strong push towards Red because we white balanced against Cyan?

(This should not be a surprise, right?)

 

Now we are going to Fine-tune this wb preset and shoot a photo with it.

Fine-tune the wb preset by pushing the cursor all the way right to A6, B0 for max Red.

(If you don't know what I'm talkng about here, then oh groan you gotta rtfm.)

Shoot a well-exposed photo of anything. Really Red result, eh?

Pull the card and read the multipliers: 5.15, 1.00, .81, 0.00.

Wow, the wb is even Redder!

 

So now what are we going to do? Rinse & repeat.

 

1. Select and load the photo you just took into the wb preset slot.

2. Keep your Fine-tuning set to A6, B0.

3. Shoot a well-exposed photo of anything.

4. Pull the card and read the multipliers: 5.66, 1.00, .73, 0.00.

5. GOTO 1.

 

I'm at 6.21, 1.00, .64, 0.00 when I stopped to write this up.

How far will the Red multiplier go?

I don't really know.

 

When I've done this in the past, I think I've given up after about 15 reloads into the wb preset slot.

 

And yes you can use a Yellow screen or a Magenta screen to force a Blue or a Green wb setting. I've never gotten too far with the Blue. It always turns out more cyan-ish. But I'll try again. The Green has worked out well. And the Red too. So far, I've never gotten a pure Green or pure Red. There's a reason for that but I don't know what it is.

 

I used this a modfication of this trickery to set a WB in my modified D600 and D610 to produce an almost Unitary WB (green) because it enables you to better expose an ultraviolet photo in a Nikon. But sometimes it is just fun shooting in Red or Blue or Green.

 

Edit: added "a modification of".

 

Very Red Photo

But note that bit of green & yellow in the weather screen, lower right.

Wait, are those numbers green? Or do they just look green because I know they are supposed to be green?

500_9761.jpg

Link to comment

Camera multipliers: 7.996094 1.000000 0.648438 0.000000

 

Ran it twice more ---- but I think I hit the limit!!!! No changes now !!

 

Camera multipliers: 7.996094 1.000000 0.648438 0.000000

Link to comment

Went for blue and got: Camera multipliers: 0.546875 1.000000 7.996094 0.000000

 

The blue photo does not look as blue as does the red photo look red.

Oh well. It's still very blue.

Link to comment

Working on the Green.

So far have this: Camera multipliers: 0.546875 1.000000 0.648438 0.000000

And cannot get below it. So have reached the limit on the Green.

 

But why did I think I was going to get UniWB this way? I am not getting that! At the moment I cannot remember what fluffery I pulled when Fine-tuning to get near UniWB. I'll figure it out eventually.

Link to comment

1) Yes, the numbers in the weather screen looked slightly green'ish to me even before I read your text asking if they looked green.

 

and,

 

2) I'd like to try this red WB for better UV exposures - but I find its a bit of a hassle to have to change WB settings for every shot I take... when shooting those multispectral sets. I like the idea though - and will probably try it out when next I may shoot UV only images.

 

and,

 

3) I don't know what your rtfm abbreviation above stands for, but if its what I read it as, it made me actually lol :D.

Link to comment

rtfm == Read the Fascinating Manual !! A commonly used abbreviation amongst Old Unix Hackers. And this Old Unix Hacker has recently had to read the danged manual because she forgot some of the nuances of awk. I was using it to write re-naming shells for my 50,000 badly named UV files.

 

Interesting to think about shooting in Red for UV. Might work if it does not oversaturate? I suppose if you keep the Picture Control on a very neutral low saturation setting? (Red overload does tend to obscure details while shooting.)

 

But if you hate changing WB for every shot in a multispectral series, why not just shoot in Monochrome and sort it all out later? :D

I've made white balance presets for all my filters now so that I can shoot Mono and apply the correct WB later. This does require some work ahead of time to get those presets in place. And you must know how much you can push a Mono shot and still be able to pull back highlights after converting to the desired color tones. Start off by not letting the Jpg Mono histogram hit the right wall, just go right up to it. Then experiment with little wall hits until you find the stopping point. (And there's much less noise when shooting to the right and pulling back later in the converter.)

Link to comment
But if you hate changing WB for every shot in a multispectral series, why not just shoot in Monochrome and sort it all out later? :D

I've made white balance presets for all my filters now so that I can shoot Mono and apply the correct WB later. This does require some work ahead of time to get those presets in place. And you must know how much you can push a Mono shot and still be able to pull back highlights after converting to the desired color tones. Start off by not letting the Jpg Mono histogram hit the right wall, just go right up to it. Then experiment with little wall hits until you find the stopping point. (And there's much less noise when shooting to the right and pulling back later in the converter.)

why not just use UWB and save yourself the trouble of different WB for each filter, which can shift when lighting changes? It's also provides a more accurate and consistent histogram.

Link to comment
But why did I think I was going to get UniWB this way? I am not getting that! At the moment I cannot remember what fluffery I pulled when Fine-tuning to get near UniWB. I'll figure it out eventually.

??? Did I miss something here?

go back in time to the UWB write up we did a few years back.

Link to comment

Shane, where is that write-up?

 

But I was referring to obtaining UniWB by manipulating Nikon Fine-Tuning in the WB Preset D Slots.

Link to comment

I think I missed something... what is UWB? And UniWB?

 

Re: shooting in monochrome to avoid multiple WB preset changes... I like the idea, and I've considered it before, but I don't know how the in-camera monochrome is set (green channel bias/basis, other?), and how it would translate to the resulting exposures in different wavebands. I know, I know - I should just test it after all and see for myself. Maybe I'll try that in my next shoot.

Link to comment

UWB and UniWB are short for Uni White Balance. White balance is typically employed by adjusting multipliers for the Red and Blue channels, leaving the Green channels at unity. For instance, a scene with tungsten light will be rich in red light so the required white balance to correct the redness of the light requires more Blue and less Red signal. For simplicity, the B multiplier must be greater than 1 and a R multiplier less than 1. These multipliers basically just multiply the R and B data captured.

To implement a UniWB is effectively implementing no WB at all, as all multipliers are equal to 1. This has the effect of producing a histogram that more closely matches RAW data as opposed to a white balanced jpg output, allowing more accurate exposure determination.

 

"Shooting" in monochrome is misleading as you are shooting in colour and then applying a "Picture setting" which basically just desaturates the colour image, after WB has been applied to it (unless you own a specially modified digital camera with Bayer array removed or a Leica Monochrome)..

Link to comment

Just want to add to Shane’s explanation: Raw Digger’s “raw composite” shows a file in UniWB with all multipliers equal to 1.0. And Dcraw’s -r 1 1 1 1 option produces the same UniWB.

 

***********

 

"Shooting" in monochrome is misleading as you are shooting in colour and then applying a "Picture setting" which basically just desaturates the colour image, after WB has been applied to it.

 

But the monochrome histogram is the same for any WB setting. (On Nikons anyway. Haven’t looked at my others in Mono.) So it seems the WB setting is disregarded in Mono? And thus Mono is a useful proxy for UniWB.

 

No, I was wrong. I had temporarily thought the preceding statement was true because there was not a lot of difference between the various WB settings I was experimenting with (Auto, Incandescent, 5000K) for the particular test scene I was shooting. When I used an extremely weird WB such as the Red (7.996094 1.000000 0.648438 0.000000) from above, then the Monochrome histogram did change.

 

But it is interesting just how close the Monochrome histograms are for WB settings which are not too far apart.

And I have found using Mono makes it much easier to get a good exposure under UV-pass filters or UV/B/G-pass filters where red or blue (respectively) tend to oversaturate the result and obscure the details.

Link to comment
  • 4 years later...

SAVE THIS SPACE FOR an attempt to explain my WB push for UV.

It will take me some time to figure out what I did for my converted Nikon D600 to get the current multipliers. 

 

From above:

Start with displaying a 40% saturated color field (JPG or TIF) on your monitor screen.

You are going to make a white balance against this color field.

  • To move towards red, use a cyan screen (153, 255, 255).
  • To move towards blue, use a yellow screen (255, 255, 153).
  • To move towards green, use a magenta screen. (255, 153, 255).
  • To move towards uniform white balance, use a screen which matches your camera's native neutral grey.
    It will be magenta looking, also.

    (Finding your camera's grey point is a entire topic I cannot write just now. Try looking it up.
    Also, Jim Kasson's excellent instructions are here: LINK. Raw Digger is required.)

 

Next step figure out what color screen to WB against in order to move a UV photo is the right direction. For a Nikon full spec cam.

Experimenting now.

 

Nikon D610 + UV-Nikkor + BaaderU UV-Pass Filter + Sunlight

Shoot Spectralon or PTFE.

Retrieve raw color of Spectralon from Raw Digger. (No WB applied.)

 

I ran out of light.

 

Link to comment

You might get cleaner results by using monochromatic or bichromatic narrow-band light sources rather than monitor screens. Perhaps combinations of red, yellow, green, cyan, violet LEDs could be employed. Magenta could be red+blue. Yellow could be monochromatic yellow or it could be red+green. Light could be combined by mixing behind frosted glass.

Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...