Histogram in 20d-help please

[gmulb]

Is there a way using the 20d to view a histogram of a scene prior to shooting it? I know how to view a histogram of a picture I have taken.

I have looked thru the manual but haven't found an answer,hope some one can set me straight on whether or not this can be done.

[morehtml]

No you have to take the picture then review the pic. If you don't like the histogram (ie exposure), then change the settings and shoot again.

The camera doesn't have the info for the histogram until you take the pic and record it in the camera's memory.

[lostdoggy]

Well let me start by saying this, you're shooting in digital format and CF are getting cheaper. Take the picture and then check the histogram.

And to answer your question, NO you can't. DSLR's sensor are hidden behind a shutter and is not exposure until that shutter is open. As such it can't generate a histogram of what it can see.

[Jaymz]

It would be really sweet if the 20D had a live histogram in the view finder.

[mikegoat]

It would be really sweet if the 20D had a live histogram in the view finder.

That would require an open shutter with a live sensor...

[RichardtheSane]

That would require an open shutter with a live sensor...
I'm sure they could find a way of doing it without using the main sensor
But it would require another sensor just for histogram viewing that moved out of the way at the same time as the mirror.
Possible, but impractical :)

[foxbat]

I'm sure they could find a way of doing it without using the main sensor
But it would require another sensor just for histogram viewing that moved out of the way at the same time as the mirror.
Possible, but impractical :)It would only ever be a very rough guess as the histogram depends on light received at the actual time of the exposure. No electronics can see into the future.

[PacAce]

It would only ever be a very rough guess as the histogram depends on light received at the actual time of the exposure. No electronics can see into the future.

If the histogram is real time, then it should be accurate enough. AAMOF, it'll be as accurate as he image you see in the viewfinder a split second before pressing the shutter button is.

As for a camera having a separate sensor for a live histogram display, the new Olympus E-330 EVolt is such a camera and it's a DSLR camera. I'm not sure if it displays the histogram in real time (it does display the live image on the LCD screen) but if it doesn't, there's no technical reason why it couldn't. Kodak has a P&S camera that can displays the histogram before the image is actually captured.

[pault107]

If the histogram is real time, then it should be accurate enough. AAMOF, it'll be as accurate as he image you see in the viewfinder a split second before pressing the shutter button is.

As for a camera having a separate sensor for a live histogram display, the new Olympus E-330 EVolt is such a camera and it's a DSLR camera. I'm not sure if it displays the histogram in real time (it does display the live image on the LCD screen) but if it doesn't, there's no technical reason why it couldn't. Kodak has a P&S camera that can displays the histogram before the image is actually captured.

Check this:

http://www.dphoto.us/news/node/2051

[mcmustang]

To do a histogram of the shot, the camera needs to "see" the entire scene, which changes with zoom, lighting, distance, etc. I think you should just take a test shot and make adjustments from there. I mean, it's not like you're wasting film or anything...

[2manyPix]

Talk about histograms.....

I've had to edit almost all my indoor shots 'cause they've come out too dark. It's the same thing each time: Mids slide to the right, highlights to the left to lighten up the picture. After the adjustment you can see more vibrant colors, better details....a lot of stuff that was "missing" in the original.
Here is a resized crop before and after just as an example:
http://claireandjoe.com/potn/before-adjust-histogram-small.jpg http://claireandjoe.com/potn/after-adjust-histogram-small.jpg
and the original histogram:
http://claireandjoe.com/potn/histogram.jpg

Exif says:

Image:
Flash fired
1/60s
f/5
iso 400
exposure bias value 0.00 EV
Metering mode Pattern
colorspace sRGB
Exposure program: normal
Exposure mode: Auto
White balance: auto white balance

Canon Maker Notes:
Focus Mode: AI Focus
Easy Shooting mode: Full Auto
contrast: high
saturation: high
sharpness: high
Metering mode: Evaluative
Flash bias: 0 EV

How can I correct this in my camera's settings so I don't have to go through and post process 300+ pictures?

Joe

p.s. Just a thought, but could my UV filter (clear, no shading) cause metering to get confused? :)

[Jon]

Your example is metering essentially caucasian skin tones, which are lighter than the "average" tone a camera's expecting. To allow for that you'd need to open up a stop or so.

[2manyPix]

"Your example is metering essentially caucasian skin tones, which are lighter than the "average" tone a camera's expecting. To allow for that you'd need to open up a stop or so.



Thanks for your tip, Jon. I've not messed around with metering too much--that's sort of the forgotten function for me 'cause I don't understand it. If I were to turn the settings to P (for example) instead of Auto, which type of metering would be optimal for indoor snapshots of persons with similarly light complexions :)? The pic I posted here was shot w/the EF-S 17-85mm 4.0-5.6 lens so it's not going to open up much more, and the camera was set to auto mode giving me almost no control of the metering. Is there a way to trick the camera into metering a darker portion of the room, say exposure lock on a darker section of the room? EXIF says 1/60s, f/5, iso 400 + flash fired, which would otherwise seem open/slow/bright enough for an indoor snapshot. :-/

Along the same lines, can someone please explain the little flash exposure slide bar? Does it only come into play when the flash fires? Does it make the flash brighter/weaker? Is it a function of the camera's built in post-processing? And is it somehow tied to the aperature/shutter speed?

EDIT: Found this link on Exposure Compensation to answer that last question: http://www.photography-on-the.net/forum/showthread.php?t=122609

In addition, Canon has this example in their tutorial:
http://web.canon.jp/Imaging/enjoydslr/p_4_001.html

Maybe I should change my username to 2manyQuestions. ;)

Joe

[Jon]

That's the type of situation Exposure Compensation can be useful in. Whatever auto mode you're in (assuming not Basic Zone), dial in '+' some when you're shooting something light and the camera will adjust. Also take a look at the histogram for your first shot (while in "Review", press "Info" until you get a histogram along with the picture and you'll get histograms with all reviews and chimp shots) and dial in EC as needed ('+' to move it to the right, '-' to move it left) to get good exposure.

If you want to meter one place and expose for another, the little '*' on the back locks exposure (unlessyou've begun playing with CF 4-1). The "flash exposure slide bar" is also a regular exposure slide bar - it shows the exposure compensation or flash exposure compensation you're using, and it affects the shooting conditions (changes aperture/shutter/flash strength) based on how much you tell it to use.

[foxbat]

You could also try partial or spot metering modes. In this type of shot the exposure is being metered from a pre-flash and evaluative mode will take into account the darkness surrounding the subject. Partial/spot will meter from the face of the subject if you keep it centered.