Troubles with Exposure Setting

[throbinson]

I have had this camera (Canon Rebel 300D 6.3MP) for about 8 months now and its

worked great.

 

However.... past 3 weeks I have been having a problem with the quality of the

image and it being too dark.

 

If I take a photos and the light meter (built in) is set dead center, the image

seems to come out a bit darker than it use to.

 

Weirder still... I had a buddy come over and help me test the new lights I just

got (55w 5000k Fluorescents 250w equivalents) and I took the picture, and I

checked the LCD display and they looked ok. I zoomed in on the LCD to check

focus and light and still seemed ok. I dump the files to my computer and they

were too dark to use. Can only lighten so much because they lose detail and look

like poop.

 

When I shoot, 1st thing I do is clear all camera settings, so when I shoot, no

weird settings are in place from the previous shoot.

 

I've checked the LCD brightness and it's at default, shooting mostly high

quality JPG, and a few RAW since the problem occurred. Inside and outside.

 

Any ideas? Do the sensors on these need 'tuning' ever so often?

 

Thanks

[rainer_t]

Can you post a (reduced in size) sample with exif data intact?

[throbinson]

exif data... is that all the stuff like iso, f, lens etc? I can give it a try....<div></div>

[throbinson]

Ok... the photo, as you can see, done at about noon, and not a single cloud in the sky. I was doing (in this case) HDR shots for practice because just learned about them. 3 shots, 1 under, 1 over and this one which should be right in the middle.

[adam_gifford]

have you checked them with a different computer? It doesnt look terribly dark to me, maybe

only slightly.

 

and have you checked that you didnt inadvertantly nudge the EV settings?

[rainer_t]

Ok, so the image was taken with f/5.6 1/800sec 100iso. This is exactly the exposure the sunny-16-rule would give for this situation.

 

Personally I don't think the exposure is wrong ... it could have a bit more contrast, but thats about it. Any chance you played with the parameters (especially contrast) lately?

 

Oh, btw ... the internal LCD display isn't a good tool to check exposure ... look at the histogram instead.

 

Another thought ... any chance settings on your computer have changed?

A miscalibrated computer display can cause exactly the problems you describe.

[throbinson]

Ah, tried on 2 computers, MAC and PC as well as used the same computers to check older photos I took to see if they looked darker.

 

Hmm... I have a few from that shoot where they were fine on the LCD but not the computer by a long shot. Was using strobes though with 2 lights aimed at the subject (250w equivalent 5000k). I don't have the budget yet for a flash meter, so took about 12 practice shots which is why I was zooming in on the LCD to check exposure... but didn't post it because the exif data would probably look 'off' as a result.

 

The image I attached, for direct sunlight at noon, seemed grey and flat for sure. As I mentioned, I do a full camera reset before every shoot and format the memory card as well... just doesn't seem 'right' the way it looks.

 

... the HDR I created looks pretty darn good but... thats another thing. :)<div></div>

[rainer_t]

Your 2nd sample is f/5 1/60sec 100iso Manual-Exposure.

 

So in this case, you were in command (not the camera). As said ... judging exposure by camera LCD isn't a good idea. Use the cmaera histogram instead.

 

If you have used a flash for the 2nd sample, it might have fired too late eventually.

[trebor_navilluso]

Thomas:

 

Your first posted shot is perfetly exposed. It's a middle grey subject adn the meter tries to make everything "well middle grey". And the blue sky is so close to middle grey luminance that we used to use it to meter off of with slide film. So yeah you have a shot with no contrast but it's exposed properly.

 

Now the second shot appears to be about 3 or 4 stops underexposed. Here's the thing, you can't look at the LCD to determine correct exposure, just framing. Use the histogram for determining exposure. If the histagram shows properly exposed shots and the monitor shows underexposed then start troubles shooting the monitor/calibration.

[throbinson]

Well, like I said, no flash meter... hence the LCD... I'm still learning how to read that histogram thing.

 

But... for example #2... I know the LCD isn't overly accurate, but, looked way way better than the image when on the computer, that's what confused me totally.... I could see a bit darker/lighter than the LCD but as you can see... very unusable shot on this one. He's East Indian so was expecting him to be dark, but... bit too dark.

 

Well.. I will look into histograms more to figure that stuff out and give it another try... hoping the strobes aren't firing too late... if they are is there a way to compensate for that without letting too much light in?

[rainer_t]

This thread has some nice links on histograms ...

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=003tZE

 

also, a Pnet search with the term "understanding the histogram" will

dig up a lot.

[JeffOwen]

You are right the histogram says you have well underexposed the shot. My guess is that there is a custom setting you have altered.

 

I have taken your shot and displayed some of the details and also done some quick correction using levels and 'shadows & highlights'.<div></div>

[throbinson]

Thanks for the help/link... I'll go read up on Histograms.

 

I'm still going to keep an eye on that LCD issue... again I know it's not accurate, but, it's never been THAT off. Like I said... I have no flash meter so couldn't really set the exposure like I normally would, just took test shots until the LCD showed a decent looking pic... but wow... very off. :)

[jason_hall4]

Never Never use the LCD for exposure, no exceptions. Only the histogram will do. BTW, the amount of ambient light changes how bright the image on the LCD appears.

 

Jason

[alan_myers]

Hi Thomas,

 

Everyone is absolutely correct here. You *must* simply forget about the LCD image review when it comes to checking exposure. It's next to useless, no where near accurate enough to judge exposure and way too prone to being influenced by ambient light. You *must* learn to use the histogram. It will tell you a great deal more accurately what's right or wrong about your exposure settings.

 

Let me give you an example. Last Sunday I was shooting out doors all afternoon. Throughout the day I used the LCD a few times to change menu settings, check histograms, etc. It was a bright day, so I had to change the LCD to maximum brightness to read the menu at all, or to have any chance of seeing the histogram. I did not use image review to judge exposures.

 

Last evening I was using the same camera in exactly the opposite situation: Indoors, by rather low available light. Following up on the first handful of shots I glanced at the image review and was immediately concerned I was greatly over-exposing. Well, that wasn't the case. I'd merely forgotten to turn the LCD brightness back down after the outdoor shoot.

 

In the dim lit conditions, it probably should have been -1 or -2 brightness instead of +2 where it was set, to have any hope of even approximating the exposure during image review. But even if it were set ideally, I knew from experience I still couldn't trust image review to give me any sort of feel of exposure accuracy.

 

So, I switched on the histogram and breathed a sigh of relief that the exposures were actually good. I'd used a gray card to set exposure, which is about the most accurate way short of a good incidence meter.

 

So, simply forget about using image review on the LCD to make any judgments about exposure. Learn to use and stick with the histogram for feedback. Your life will be much simpler.

 

By the way, go get a gray card. They only cost a few bucks. Since you are using constant lights, you can just have the subject hold it pointing toward you and move (or zoom) in to meter off it. You can also use it to set an accurate custom white balance, at the same time.

 

Which brings me to another thing. With constant lights you don't need a flash meter. Any meter will do.

 

However, I also gotta ask about the fluorescents you are using... Are they made specifically for photography? The reason I ask is that standard fluorescent bulbs actually flicker constantly, which makes them a pretty poor choice for studio lighting. It's fast enough that our eyes can't see it, but still manages to mess with camera meters. Even if using non-photo fluorescents, though, it should cause so much of a missed reading as the second and third image examples you posted. Fluorescent bulbs specifically for photography are now offered that eliminate this flickering effect.

 

The linked photo also doesn't look very much under-exposed to me. At least it's nothing a little tweaking in Photoshop couldn't improve. I would judge it to be maybe 1/3 to 1/2 stop under exposed, is all. (In fact, it's a good example where "expose RAW to the right" theory would solve the problem... Google for that if you want to know more. In fact, if you Google for "histogram" you will likely find a lot of guidance for using that tool to it's fullest, too.)

 

Which brings me to another thing. Are you shooting RAW files? If so, you have more latitude to correct exposure during post-processing, than you do if shooting JPEGs. Still, it's best to get accurate exposure to start with, since that will help keep noise to a minimum.

 

Another place where things can go astray is during RAW processing. If your RAW converter default accidentally got set to reducing exposure the on all your shots, you could be fooled into thinking you are frequently under-exposing the images.

[throbinson]

I was thinking of getting a grey card... though you mentioned setting custom white balance with it, I always thought you did that with something white, no?

 

From my above example, I was using constant lights, plus, strobes... thats why I was using the LCD because I don't know how to use the histogram yet... actually after reading a few articles on it I'm still not overly sure how. :) Think I need to find a few better articles.

 

Light wise, I have a pair of fluorescent 55w 5000k photo bulbs, 250w equivalent. I had a pair of umbrellas, but diffused the lighting too much so just ordered off eBay this week a pair of 10" Aluminum reflector pots. Should help with a harder light source since I'm a fan of the harsher shadows.

 

RAW vs JPG wise... I shoot RAW for still lifes, but anything where its people or oudoors I tend to shoot JPG more often just because after doing a few shots I have to wait for the memory card to write... it's a Sandisk Extreme III 2GB so a pretty fast card, but I hate when I go to take a shot and its still flashing away.

 

RAW converter... hmm, I use Photoshop CS3 for everything, and I have a MAC and PC... though, then again those shots were JPG so I guess not the issue... hmm, well, I am going to read more on the Histograms, and yes a grey card was next on my list because well... those light meters are WAY more $ than they should be... seriously... my iPod has more features and costs less. :)

[jason_hall4]

For many photogs the histogram has replaced their lightmeter altogether. There are those who are dyed in the wool lightmeter users. Its all in what you get used to using and you fill comfortable with. Some folks just feel the shutter should never open until every thing is as close to perfect as you can get it.

 

I have a lightmeter and carry it in the bag with a good battery in it. It gets used once every couple of months. The most I use it for is to walk around a room to get an idea what the ambient light is giving me.

 

 

As far as the grey vs white card goes, the grey card is used for exposure. Either one can be used for white balance as long as they are neutral. Some will say you need grey for white balance so that the exposure is correct on the shot taken for the WB setting. but all I can say is that in my experience is that white works just find. The meter in the camera will underexpose it if it fills the frame. Personally I shoot the card as a smaller portion of the frame and then use the "eye dropper" to set WB in post processing. Then I sync the setting with the rest of the photos with the same lighting.

Your LCD can and does work to get lighting ratios, but takes some practice to get that right to. Lighting ratios is where the lightmeter is handy; personally, I still do well with the LCD. However the LCD on the camera I am using is a bit larger than yours.

 

 

JPEG V RAW,

All depends on what you are comfortable with and what meets your needs. I use RAW only now that I have Lightroom. Just be SURE you practice NON Distructive editing.

 

 

Histograms,

yeah, it took me about five or six articles before I really got it. Now its like reading my own name. James...Jack...Jim...well it starts with a J.

 

:o)

 

 

Jason