7 photos to help Histogram Red Channel frustration - I need help or is it the camera.

Started Jul 9, 2007 | Discussions
LilKnytt
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7 photos to help Histogram Red Channel frustration - I need help or is it the camera.
Jul 9, 2007

I'm loosing it yet again. Just as soon as I think I've gotten it better I'm pulled back to reality & end up down over it.

I know my camera exposes/meters in an interesting manner. I work with it, around it.... I try to find a midway - doesn't work. My histograms are always a pain to me. OK, they help at times - but other times they just make me frustrated.

I shoot aRGB. So the first time I notice is that when I look at the files in NX after seeing them on the LCD screen - they change. So the first thing I do is to make them sRGB with Relative Colorimetric profile.

So I just did another boring (& frustrating for me) test. All shot at 650 ISO. I wanted to use available light so that my histograms wouldn't be "funny" due to the flash.

After much testing I came to the conclusion that if I wanted to work at f/8 on my 70-200VR I needed the 650 ISO. So all shots are at f/8 650 ISO on the 70-200VR lens. From much testing I found that 1/50 s was where I was best in Manual (according to my experimenting that is).

Then I chose to test the D200 in Spot, Matrix & Center Weighted Metering in Shutter Priority & Aperture Mode. Aperture set at f/8 & Shutter set at 1/50 s. It's somewhat frustrating to see the result the camera gives me.

On, due to the fact that this is a test I've set the camera to normal in all settings past aRGB. I shoot RAW. No pp past aRGB to sRGB RAW & jpg.

The issue here is not that I can correct it in pp - cause I know I can. The issue is why am I getting the result I'm getting. The channels - especially red - spikes over 255. What am I doing wrong?

1/50s 650ISO f/8 manual mode

The next three are shot also at 650 ISO f/8 in Aperture mode

1/40s Spot metering

1/30s Matrix metering

1/45s Center Weighted metering

The next three are Shutter Priority 1/50s 650 ISO

f/7.1 Spot

f/6.3 Matrix metering

f/8 Center Weighted metering

My question - why am I getting the channels spiking the way I do here? Please advice as to what I'm doing wrong. All shots taken on tripod right after one & other. All metering sensor in the same place.

Please advice.

Lil

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funnelwebmaster
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to LilKnytt, Jul 9, 2007

what's a "channel spike?"
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Kent Johnson
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to LilKnytt, Jul 9, 2007

Hi Lil,
I read your post 3 times and I still can't tell what you are asking, exactly.

Are you asking how to meter to avoid blowing the red channel? If so, this scene is hard to meter and a grey card would be invaluable in maintaining your sanity.

Ask yourself this: If you were the camera's meter, what would you use as a reference to meter in each of the modes?

Not blowing the red channel is as easy as simply watching the histogram. What am I missing?
-Kent

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Muntz
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to LilKnytt, Jul 9, 2007

Hey Lil. Don't think you're doing anything wrong. Same exact thing happened to me a few weeks ago with my D2Hs with very similar flower shots. They were red flowers exactly like yours and the red channel was blown way out. It was obvious on the lcd playback and on the histograms that the red channel had blown highlights. I compensated by lowering exposure and still ended up having to pp.

But I was using center weighted. When you used spot did you meter off the flower (because that should have kept the blown red channel in check) ?

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digitall
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to LilKnytt, Jul 9, 2007

Lil, virtually every digital photographer experiences this and the phenomenon is due to the way digital cameras respond to red, green and blue. Red typically over-exposes and this is a problem with a predominantly red subject. What you have established is that the various metering modes give incorrect exposure for the flower and this is established by viewing the red channel histogram or viewing the picture on your monitor. What you must do is simply compensate by cutting the exposure until there is no 'spike' in the red channel.

Unfortunately in bright, direct sunlight, this can mean cutting exposure by such a degree that the whole picture may look rather under exposed. You may be able to photograph under more favourable conditions (softer daylight) or use fill-flash etc. However, you can often obtain satisfactory results by accepting a little over-exposure in the red channel. I've had to cut exposure by well over a stop when photographing red flowers in bright light and it is frustrating.

If you are finding your meter tends to over-expose all the time then you can adjust for this through your menu system. On the D2X this can be done for each metering mode (I think) and it may be the same for the D200.

I hope this is of a little help.
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LilKnytt
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Spot metering off the flowerRe: 7 photos to help Histogram Red Channel frustration -
In reply to Muntz, Jul 9, 2007

Muntz wrote:

But I was using center weighted. When you used spot did you meter off
the flower (because that should have kept the blown red channel in
check) ?

Hi Muntz, I was spot metering off the flower. I've noticed that my camera seems to have a tendency to spike the levels off the chart all the time. Not just the red channel.

What am I doing wrong???

Lil

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LilKnytt
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to funnelwebmaster, Jul 9, 2007

funnelwebmaster wrote:

what's a "channel spike?"

It's a spike in the histogram in a specific or all colors.

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Steve Bingham
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Lil
In reply to digitall, Jul 9, 2007

Learn to use the camera multi-channel histogram on shots like these. Reds in shade work better (less clipping). You will also find that you will need to cut exposure by as much as a full stop! This will under expose parts of the picture that will be easier to retrieve than clipped reds (which can never be retrieved). In film days, when using Velvia, I had to print with a "red mask" to cut the red saturation when printing on Cibachrome. This was a very expensive and tricky solution but all good custom printers knew the trick.

Use the exposure compensation dial on top of the camera - and don't forget to reset it when finished!!!!!!!! if you are serious about exposure, learn to live by the camera histogram. It will save your butt! If it is a product shot or a still shot a tripod and multi exposures will also solve the problem. High dynamic range (HDR) in PC CS2 or CS3 (better) can help in this regards. You are learning to solve serious problems. Congrads!

As your reds get lighter they rapidly approach 255 where no more information is available. Try this. In PS use the Window-Info pull down menu. Take the dropper onto a red area and read the info. Now Lighten the reds (Image-Adjust_Hue/Saturation_Select Red, then Lighten) and watch the reds turn to pink and totally clip at 255. A nice medium red is 185-0-0. A dark red 130-0-0.

That's why reds must never be clipped. Some raw converters, such as older Nikon versions, were so anxious to give you good reds that this clipping was very common in the default mode - and one of the reasons I went to ACR (a long time ago before I learned more about finessing the end product). Granted you can adjust conversion to taste and the ACR default is pretty flat in ACR. Which once more brings us back to the operator, rather than the software.

Steve Bingham
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nicola
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to LilKnytt, Jul 9, 2007

Try to compensate with White Balance, a trick I learned watching Ron Reznick's Sureshot System Videos!!!

My 2 cents ...

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Krishnan V
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Dial Down White Balance to hold Red
In reply to LilKnytt, Jul 9, 2007

Ron Reznick and Sureshot system is highly recommended !

http://www.digital-images.net/
http://www.sureshotsystem.com/

Here is what you can do to hold the RED channel.

1. Change White Balance (WB) to Degree K mode.
2. Take test shot and look at the three channel Histo

3. If the Red is blown reduce the Degree K value manually and try the shot again till the histo is within 255 on the RED channel.

Works for me

Best Regards
---Krish
http://krishphoto.com

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LilKnytt
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Thanks Steve, just confirming what you recommend doing. Re: Lil
In reply to Steve Bingham, Jul 9, 2007

OK, in order to keep my reds, continue using my multi-channel histograms ( I was working with them) underexpose the shot - to where the reds aren't clipped. I was also working in even shaded light. But I have WB in Auto in the camera.

OK, 1st question - why does my histogram in camera & in NX not correspond? Why does the histogram change? Does it have to do with LCD readout being more of an sRGB or jpg as opposed to an aRGB? I'm shooting aRGB RAW -

2nd question - when I convert the aRGB file to a sRGB file the histogram changes yet again. What to go by - the camera histogram (multi-channel) is what you write. OK - but why does it not correspond in NX?

Then go in into CS3 (the version I have), open file - which opens in Camera Raw 4.1. Convert into sRGB for workflow. Convert into a jpg (or TIFF). Work the file - check the numbers (I'm a baby in CS3 - I have a long way to go to work this out)

Steve Bingham wrote:

You are learning to
solve serious problems. Congrads!

Thanks - just got to learn when to take on the battles - - this week's not it. Ah well, now I've started so now I have to learn.

That's why reds must never be clipped.

OK Steve - lesson is - do not ever clip reds. Underexpose & get the reds right in camera, lighten in pp. Got it. Same with whites - right?!

Anyhow, baby steps tonight & this is what I came up with. I used one of the other underexposed shots I had. This one is shot at 320 ISO at 1/80s f/8. Any better?

Thanks,

Lil

This one edited in NX

This one in CS3

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LilKnytt
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Re: 7 photos to help Histogram Red Channel frustration - I need help or is it the cam
In reply to nicola, Jul 9, 2007

OK, I will try that as well.

Lil
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LilKnytt
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Gray card or ExpoDisc? Re: 7 photos to help Histogram Red Channel frustration -
In reply to Kent Johnson, Jul 9, 2007

Kent Johnson wrote:

Hi Lil,
I read your post 3 times and I still can't tell what you are asking,
exactly.

That speaks highly of my communication skills.

Are you asking how to meter to avoid blowing the red channel? If so,
this scene is hard to meter and a grey card would be invaluable in
maintaining your sanity.

OK, gray card needs to be bought or should I go for one of those ExpoDiscs?

Ask yourself this: If you were the camera's meter, what would you use
as a reference to meter in each of the modes?

Well, I did tell the what to meter - but no reference....

Not blowing the red channel is as easy as simply watching the
histogram. What am I missing?
-Kent

What you're missing is my frustration in trying to achieve an acceptable histogram without getting clipped reds. I worked ISO, shutter speed etc. I also left it to the camera to determine either shutter speed or aperture. In either case the camera exposed incorrectly & I kept getting clipped reds. I wanted to know what was wrong. What I have learned is that I need to underexpose to get the correct reds & forget about a histogram the way I was looking for one.

What you were missing is that I kept trying to achieve a widely distributed histogram, but by doing so - the shots are over exposed & my reds clipped. Thanks for trying.

Lil
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BasilG
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Re: Thanks Steve, just confirming what you recommend doing. Re: Lil
In reply to LilKnytt, Jul 9, 2007

Maybe I'm missing something, or maybe I don't know enough, but I don't think you can shoot "Adobe RGB RAW" - RAW is RAW. The other color spaces are there for jpgs (so when you open the RAW, it's being converted into one of the color spaces - that's also why your histogram may change from RAW to JPEG - the JPEG has less capacity to store information than RAW). I usually use color space I (sRGB I) for reds on my D100 when shooting JPEG...

This looked all blown red when shooting in color space III, space I did a much better job:

BG

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OleThorsen
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Re: Thanks Steve, just confirming what you recommend doing. Re: Lil
In reply to LilKnytt, Jul 9, 2007

LilKnytt wrote:

OK, in order to keep my reds, continue using my multi-channel
histograms ( I was working with them) underexpose the shot - to where
the reds aren't clipped. I was also working in even shaded light. But
I have WB in Auto in the camera.

OK, 1st question - why does my histogram in camera & in NX not
correspond? Why does the histogram change? Does it have to do with
LCD readout being more of an sRGB or jpg as opposed to an aRGB? I'm
shooting aRGB RAW -

The in camera histogram is AFAIK based on the embedded 8 bit JPEG which has less colour depth than your NEF converted in NX, so even though your camera histogram shows the channel as blown, it could be fine when you open the NEF in NX.

2nd question - when I convert the aRGB file to a sRGB file the
histogram changes yet again. What to go by - the camera histogram
(multi-channel) is what you write. OK - but why does it not
correspond in NX?

Changing colour space in PP will give different histograms, due to different gamuts.

OK Steve - lesson is - do not ever clip reds. Underexpose & get the
reds right in camera, lighten in pp. Got it. Same with whites -
right?!

Lil, you doesn't necessarily underexpose just because you choose another exposure than your camera's exposure meter suggests.

Anyhow, baby steps tonight & this is what I came up with. I used one
of the other underexposed shots I had. This one is shot at 320 ISO at
1/80s f/8. Any better?

IMHO these exposures are way better than the 7 exposures you first showed. With these last exposures you "smacked two flies with one hit", you saved the red channel and you emphasized the flower with the darker background.

Here is one of my examples of a red flower in the sun. I was in Manual exposure mode using Matrix metering and the first picture I made, I used the suggested F5.6 1/160s ISO100 exposure. The red channel blow a little so I reduced the exposure to F8 1/160s ISO100 and voilá

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Ole Thorsen
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Mike Horyn
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Re: Bracket the exposure
In reply to LilKnytt, Jul 9, 2007

Lil:

The Red channel tends to overexpose before the Green or Blue. You know that. So, when framing an image with a lot of red, the easiest way to obtain a great result is to "bracket" the exposure. Your Nikon has a button for this function. And while a digital exposure normally needs to be within a 1/2 stop, don't be afraid to underexpose an image like yours even more; whatever it takes to obtain the result you want. Thus, if the spot meter exposure called for 1/30 shutter, use a manual setting of 1/60 (allowing less light) in order to preserve the sensitive Red channel.

Mike

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LilKnytt
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Tack Ole Thanks for the help Ole
In reply to OleThorsen, Jul 9, 2007

Tack for helping Ole, or is it Tag in Danish? I don't remember right now....

OleThorsen wrote:

so even though your camera histogram shows the channel as blown, it could be
fine when you open the NEF in NX.

OK, so I'm back at the fact that the camera histogram is really only a good indicator.

Lil, you doesn't necessarily underexpose just because you choose
another exposure than your camera's exposure meter suggests.

I was basing that statement on the histogram's look.

IMHO these exposures are way better than the 7 exposures you first
showed. With these last exposures you "smacked two flies with one
hit", you saved the red channel and you emphasized the flower with
the darker background.

Good, cause I liked the darker ones where I can emphasize the flower -s better anyhow.

Very beautiful flower Ole. Far better than any of mine. But you've been at this longer than I have. I keep forgetting that I've actually only been at this since somewhere around January & my learning curb has been steep. Add to the fact that I'm not only trying to learn the camera, how to work exposure etc with it & pp all at once. Add the fact that I'm now trying to get myself used to CS3 as well. No wonder I have no time for the horses nor my e-mail friends any more.

Thanks for you help & advice Ole.

Ha en bra dag - I don't know enough Danish to write it in Danish. So sorry for the Swedish..... maybe you'll forgive? It's fun to be able to write a little in Swedish now & then.

Lil - the displaced Swede

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LilKnytt
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Re: Bracket the exposure
In reply to Mike Horyn, Jul 9, 2007

Mike Horyn wrote:

Lil:

when framing an image with a lot of red, the easiest
way to obtain a great result is to "bracket" the exposure.

OK, so I'll bracket red flowers from now on. Good suggestion. I don't use the bracket enough. Need to.

don't be afraid to
underexpose an image like yours even more; whatever it takes to
obtain the result you want.

Thanks Mike, I am so concerned not to do well I forget that it's not the histogram that decides what's right. It's not even anyone here - it's ME - MY VISION. If I like dark backgrounds, then I should go for dark backgrounds. Main thing is that the subject, in this case the flower, is not blown. I have some shots to go through. I keep attempting to get a wide histogram instead of looking at the individual channels.

I will rethink this & do some shots differently in the morning.

Thanks for the help & support.

Lil

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sclamb
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You are discovering the balancing act named 'Exposure' :-)
In reply to OleThorsen, Jul 9, 2007

It is worth bringing into this mix the fact that you were shooting at a higher ISO. As has been previously recommended, lower your exposure to make sure the red channel doesn't blow out, and then bring the exposure up in post processing, perhaps with some Shadow/Highlights in PSCS or D-Lighting in NX. Do remember though that the higher the ISO the more noise you will see when bringing up the underexposed areas, so you may then need to apply some NR or blur to selected show and dark areas.

Isn't digital fun though! Much easier to learn with digital that it was with film/slide.

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LilKnytt
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Re: You are discovering the balancing act named 'Exposure' :-)
In reply to sclamb, Jul 9, 2007

Hi Simon,

the higher ISO was chosen this way. I started at 200 ISO, went to 320, 400, 500, 640 all based upon what I saw as not correct histograms. It is obvious that I'm still reading the histograms a little wrong & also a tad "set in stone". Instead of going by my gut instinct, I try to appease the histogram. Not working.

The second set of shots in the thread are shot at 320 ISO I believe. The reason this came up was because someone visited my web site & pointed out that I had clipped my red channel & that fixing my red channel would help. That it would become less pp for me. OK, so I set out to fix my red channel, while trying to keep my idea of a histogram. I failed to achieve what I wanted the way I though I should do it. Instead it comes down to doing what my gut tells me to do. So I need to learn to think of histograms differently yet again.

sclamb wrote:

Isn't digital fun though! Much easier to learn with digital that it
was with film/slide.

Yes Simon, digital is fun. It's easier, yet harder. It's easier as I don't have to worry about getting film developed & don't have to worry about remember settings. Now the camera records everything for me. Film, I shot slides, cause I had no money to develop film rolls. The slides I got developed & then I only printed - as I wanted - only the shots I wanted & the way I wanted them.

Thanks for your help

Lil

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