300D - poor dynamic range w/lights

[Tom Camilleri]

I'm using two Lowell Tota-lights with 500 W bulbs and diffusing umbrellas against a white paper background. GR white card for WB and grey card for AE lock and Photoshop correction. My lens is Canon compact macro EF 50 mm. I have been placing the lights fairly close to small subjects (within three feet) and the camera seems to be able to set a correct exposure (generally at f2.5, which is minimum, sometimes higher at higher than 100 ISO). I'm shooting from maybe 2.5 feet to 7 feet from the subject.

My problem is that although the camera is able to set exposure when locking on the grey card, I am not getting good dynamic range as indicated by the histogram. While not off either end of the scale (if so exposure comp can fix), the enitre distribution is often completely in between, typically extending over 1/4 to 1/3 of the histograms tonal range. The subjects should be recording a normal tonal range. I understand that with a white background (i have tried studio grey with similar but somewhat better results) the histogram is going theoretically going to show abnormally high distribution in high range, but this often isn't happening and the whole distribution is short of either extreme. Even when the white BG shows up on the histogram, the other tones seem compressed somewhere in between instead of appearing across the whole tonal range, as they should. When correcting in photoshop, a washed out contrast can be easily corrected with autocolor, autocontrast, levels or contrast, but mid ranges are very sensitive and become too dark very easily, which is what would seem reasonable when working with an unnaturally compressed dynamic range.

Can anyone offer a diagnoses and prescription? Would using a flash fill (I have a 380EX) help to better illuminate the subject? MAybe backing up the lights and adding spots for the subject? Can flash and lights be mixed? Before I invest in more lights, would flash be easier for a newbie to get working properly?

Thanks for any insights. Any guidance toward directing experimentation greatly appreciated.

(PS- In my completely inexpert opinion there must be a serious flaw in my lighting/background set up. The amount of light seems marginal to actually capture the subject, but enough so that the white background overwhelms the camera. This is the subjective opinion of a very green person, although I have fiddled a while with photoshop.)

[Jon]

If I'm understanding you, your histogram looks like the Little Prince's snake which swallowed an elephant, with long tails and a big hump in the middle. Is this right?

How are you metering on the grey card? Have you considered using manual settings, rather than, as it sounds you're doing, one of the auto-modes? You might also try moving the lights away from the subject, and bracketing your exposures. If you're not showing anything in either the white or the dark ends of the histogram, you'd need to adjust the lighting so the key and fill lights are less evenly matched. Try setting the fill (secondary) light 2-4 times the distance of the primary (key) light, if they're the same intensities. If they're very close to the subject, with diffusion, you're also helping kill off the contrast you appear to want/need. Again, moving them back (or taking off the diffusers) will help.

[PhotosGuy]

Can anyone offer a diagnoses and prescription? Posting a pic would be an obvious 1st step?

[Tom Camilleri]

Thanks for responding. I was away for a day and then had to contend with digging out of a blizzard.

The histogram does look a bit like the snake which swallowed an elephant. It's not compressed entirely within a narrow range, though, but truncated well short of either tonal extreme. The things I've been photographing should show a distribution that extends much closer to both extremes, since they neither basically dark nor light in tone. The way I've been shooting, histograms extend over about 50-60% of the tonal range. I haven't tried manual settings because I really don't understand exposure much beyond "more light-less time."

I've been in aperture priority, mostly, but I have found since my original post that shutter priority seems to give better results. I've been shooting a G-M white card to set custom white balance, then metering by using AE lock with a G-M grey card (it has three stripes' white, grey, black) by just aiming at the middle of the grey stripe. At the distance I'm shooting, the entire card is more than 10% of the frame and I move closer to set AE lock if not. I keep the shutter button half depressed during the entire AE lock process, so if I move in the G-M grey card is not in focus. If I can get the card in the shot I do so for later photoshop correction, but this is usually difficult. With auto white balance my results are similar.


I understand you when you advise moving the lights back to increase contrast. When you talk about increasing the disparity of key and fill lights to increase dynamic range I start to loose you, since I've been just placing lights with an eye to illuminating all details without causing dark shadow areas and not thinking in terms of key and fill lights. I thought I was immersing the entire subject in a fairly even, diffuse light but I did keep one light a little further away. Both lights are positioned to the sides at about 45 degrees from the camera axis.

From what you are saying it seems I might be shooting with all fill and no key lighting, but I don't want shadows on my white paper background. Perhaps I need more lights than the two I'm using.



If I'm understanding you, your histogram looks like the Little Prince's snake which swallowed an elephant, with long tails and a big hump in the middle. Is this right?

How are you metering on the grey card? Have you considered using manual settings, rather than, as it sounds you're doing, one of the auto-modes? You might also try moving the lights away from the subject, and bracketing your exposures. If you're not showing anything in either the white or the dark ends of the histogram, you'd need to adjust the lighting so the key and fill lights are less evenly matched. Try setting the fill (secondary) light 2-4 times the distance of the primary (key) light, if they're the same intensities. If they're very close to the subject, with diffusion, you're also helping kill off the contrast you appear to want/need. Again, moving them back (or taking off the diffusers) will help.

[Tom Camilleri]

Posting a pic would be an obvious 1st step?


You're right. I'll post my next shot.

[Longwatcher]

From my experience the fastest way to get rid of shadows from backgrounds is
1. move the object away from the background.
2. diffuse the light (use a softbox or umbrella)
3. put a third light behind the target and illuminate the background itself.

#2 works better then #1 if you don't have any room. and #3 only works if you can get the light behind the target without the light itself showing.


Just my experience.

[Tom Camilleri]

Here's an example of one of my photos which shows a lack of contrast. The histogram shows pixels distributed over only the lower 65% or so of the tonal range, but it does not go off scale in the lower range. The upper 35% or so is empty.

[kb244]

Hrm You may not realize this but most Digital SLR cameras require post-processing , unlike consumer cameras which tigten the histogram to make things *pop*. Also what color space are you shooting with. AdobeRGB will seem dull on your screen, and you may want to shoot in Parameter 1 for a lil more vibrance. I usally have to add least a +15 contrast in photoshop to some pictures, and usally doing some leveling.

[PhotosGuy]

The histogram shows pixels distributed over only the lower 65% or so of the tonal range, That's because it's underexposed. The whites on your card only read 179 instead 250+.
but it does not go off scale in the lower range. That's common, at least I see it all the time. I'd rather have that & be able to correct in Levels, than have it go off the scale & be unable to bring it back.
This shot doesn't look bad after an adjustment in Levels.

[slejhamer]

Let's guess ... camera was in "evaluative" metering mode. So when it saw a mostly white scene, it did what it is supposed to do - exposed it as gray. :)

When you shoot something with lighter tones, you need to add some exposure compensation or it will underexpose. With the all-white background you probably need at least a full stop of +EC. Try that and see if it helps.

I assume your Lowell lights are continuous, but if you were using flash instead you might also need flash exposure comp.

Hope that is helpful.

[Tom Camilleri]

Thanks for your comments.

I didn't realize I could vary the color space. What setting do you recommend? I will try Parameter 1. The post processing I do on many of my shots is pretty similar to what you describe. As I mentioned, even after post processing this shot there will be problems such as a slight ruddiness on parts of the face and limbs being turned into a more saturated orange tone.

[Tom Camilleri]

Thanks for responding!

I thought it might be underexposed, but the camera was in Av and I was setting exposure lock on the grey card. Why didn't the camera come up with the correct exposure?

I suppose I should buy some more lights? I guess I'm always underexposed if the white strip is under 250? Maybe I'll try a series of manual exposures starting with a standard exposure and just walking up until I get a true white.

From playing with the camera, I suspect that if I increase the exposure rather than the light I will get overexposed shots.



That's because it's underexposed. The whites on your card only read 179 instead 250+.
That's common, at least I see it all the time. I'd rather have that & be able to correct in Levels, than have it go off the scale & be unable to bring it back.
This shot doesn't look bad after an adjustment in Levels.

[Tom Camilleri]

Thanks for your inputs.

Since I was using AE lock and aiming at the middle strip of the grey card, it should have been in partial metering mode. Maybe the metering area went off the grey stripe.

I will try a full stop +EC with evaluative metering and see what happens. My lights are continuous. Do you think I need more? Can I mix the Lowell lights with clamp mounted incandescent bulbs (I have a few lying around from previous experiments) or should I get some more lights?


Let's guess ... camera was in "evaluative" metering mode. So when it saw a mostly white scene, it did what it is supposed to do - exposed it as gray. :)

When you shoot something with lighter tones, you need to add some exposure compensation or it will underexpose. With the all-white background you probably need at least a full stop of +EC. Try that and see if it helps.

I assume your Lowell lights are continuous, but if you were using flash instead you might also need flash exposure comp.

Hope that is helpful.

[PhotosGuy]

Expose to the Right
http://www.luminous-landscape.com/tutorials/expose-right.shtml
A PRACTICAL GUIDE TO INTERPRETING RGB HISTOGRAMS
http://www.sphoto.com/techinfo/histograms/histograms.htm
Understanding Exposure - A Complex Subject Made Simple for Beginners
http://www.luminous-landscape.com/tutorials/understanding-series/understandexposure.shtml
Accurate Exposure with Your Meter
http://www.kodak.com/global/en/consumer/products/techInfo/af9/
The Grey Card:
http://home.nc.rr.com/tspadaro/The_Grey_Card.html

[Jon]

Thanks for responding. I was away for a day and then had to contend with digging out of a blizzard.

The histogram does look a bit like the snake which swallowed an elephant. It's not compressed entirely within a narrow range, though, but truncated well short of either tonal extreme. The things I've been photographing should show a distribution that extends much closer to both extremes, since they neither basically dark nor light in tone. The way I've been shooting, histograms extend over about 50-60% of the tonal range. I haven't tried manual settings because I really don't understand exposure much beyond "more light-less time."

I've been in aperture priority, mostly, but I have found since my original post that shutter priority seems to give better results. I've been shooting a G-M white card to set custom white balance, then metering by using AE lock with a G-M grey card (it has three stripes' white, grey, black) by just aiming at the middle of the grey stripe. At the distance I'm shooting, the entire card is more than 10% of the frame and I move closer to set AE lock if not. I keep the shutter button half depressed during the entire AE lock process, so if I move in the G-M grey card is not in focus. If I can get the card in the shot I do so for later photoshop correction, but this is usually difficult. With auto white balance my results are similar.


I understand you when you advise moving the lights back to increase contrast. When you talk about increasing the disparity of key and fill lights to increase dynamic range I start to loose you, since I've been just placing lights with an eye to illuminating all details without causing dark shadow areas and not thinking in terms of key and fill lights. I thought I was immersing the entire subject in a fairly even, diffuse light but I did keep one light a little further away. Both lights are positioned to the sides at about 45 degrees from the camera axis.

From what you are saying it seems I might be shooting with all fill and no key lighting, but I don't want shadows on my white paper background. Perhaps I need more lights than the two I'm using.

If you want contrast, you've got to allow something in the picture to go dark, and something to go light. But changing the relative intensities of the key and fill lights to be 1-2 stops different wojn't create massive shadows. It will help give a sense of depth to the subject. If you don't want shadows on the background, you need to move the subject away from it some, and to get a brighter background, hit it with its own light (which will also help backlight the subject). That will mean adding a light.

[slejhamer]

Thanks for your inputs.

Since I was using AE lock and aiming at the middle strip of the grey card, it should have been in partial metering mode. Maybe the metering area went off the grey stripe.


It's only in partial mode if you tell it to be. :) If you check the shot's EXIF data you will know for sure, but the default is evaluative so unless you've changed it, it's still there.

You mentioned that the gray strip was 10% of the frame; that's probably not enough when most of the frame is white, if you were in evaluative. But check your EXIF data; if it says evaluative then you'll know what the problem is. If it says partial, then it's possible that the meter missed the card.

The articles that Photosguy recommended are excellent resources.

[Tom Camilleri]

Thanks for the links! BTW, I see you use RAW format. Does it offer big advantages?

[PhotosGuy]

RAW is a "digital negative", & for me the difference is huge. I grew into photography wet processing negs & prints & the tiny amount of extra work is insignificant. Other people prefer the convenience of JPEGs. Maybe you should also take a look at this:
"Gray card: Why your meter may be lying to you!"
http://photography-on-the.net/forum/showthread.php?t=54281
In it I posted a link to:
"Why I love RAW - '53 Ford Sunliner"
http://photography-on-the.net/forum/showthread.php?t=43761&highlight=sunliner

[Tom Camilleri]

Thanks. I'll check them al out. Do you happen to know if the histogram in the D300 is luminosity or RGB?

[PhotosGuy]

Don't know.