histogram and exposure question

[Volatile]

I tried to take some outdoor portraits of my wife and son today, and the highlights are blown to smithereens. It was a bright, no cloud, full on sunny day, I was was shooting Av mode on my dRebel. Had aperature at 5.6 on my 50mm f1.8 lense, and the camera picked out 1/1600 shutter speed at ISO 100. The histogram showed a solid spread from top to bottom, with the bulk of data in the middle.

So, two questions

1. Should I have known that the highlights would be overexposed? If so, how?

2. I was using f5.6 to try to put some bokeh on the bush that was a foot or so behind them, but should I have been stopped down to f8 or f11 or more?

Thanks in advance for your help.

[dtrayers]

Bright, cloudless, sunny days are very high contrast and risk having blown highlights.

Next time look for the flashing in the LCD review screen for the blown areas. Sometimes it's ok and they're supposed to be blown to white, like bright reflections or the sun. But if you don't want it blown to white, then either dial in some exposure compensation or meter off a brighter subject.

Sometimes it's easier shooting in manual mode and look at the bar graph as you move the center focus point around the scene. You can watch it change and get an idea of the dynamic range of the scene.

[Roger_Cavanagh]

Apart from the flashing pixels to indicate blown highlights, another warning sign to look for is the histogram curve "running into" the righthand end rather than gently tapering off. The curve hitting the right (or left) end is often an indication of clipping giving blown highlights (or blocked shadows).

I believe the 300D makes its own mind up about what metering mode to use. In bright shooting situation, the 10D using evaluative metering (which I'm guess the 300D would choose in this situation) would easily blow highlights, so dtrayers advice of using exposure compensation is good.

Regards,

[Volatile]

thx for the replies. I will try exposure comp next time, and fall back to manually stopping down for added control.

Just a few months ago I was a P&S guy, and had no idea what an f number was...

is there any issue with using faster shutter speeds, analagous to using higher ISO and adding noise?

[evilenglishman]

2. I was using f5.6 to try to put some bokeh on the bush that was a foot or so behind them, but should I have been stopped down to f8 or f11 or more?


no, you should go the other way, lower number = more blur

[G3]

In addition to what everyone else has already said...

There is no "perfect" Histogram that fits every subject. The spread of data in the Histogram is going to depend entirely on the tonality of the image. What is normally referred to as a "perfect" Histogram would be one in which the entire scene averages 18% gray, with some pixels being nearly completely black and some being nearly completely white but the bulk somewhere between white and black and the largest number of those right at middle gray.

If you have a subject that is mostly white, such as a closeup photo of a bride in a white gown and veil, most of the Histogram is going to be to the right. You want to try to expose so that you don't have a "wall" up against the right or left edges, because that means that some of the data fell outside the dynamic range of the image sensor for the ISO setting. The tallest part of the Histogram indicates that the most pixels in the image were in that part of the tonal range.

If you get a meter reading from a gray card before the exposre and set your exposure according to that reading, you should be in good shape in most cases. Bracketing is still a good idea, though. Bracketing can present it's own problems, however. For instance, if you are shooting a wedding you will average shooting 250 or so pictures for an event (or more). Without bracketing, shooting RAW, that represents over 1.5 gig. I can count on getting about 70 images to a 512mb CF card in RAW, depending, of course, on the subjects. Shooting RAW and bracketing every shot, that would translate to about 4.5 gig considering that you shoot 3 shots for every one when you bracket. Plus, bracketing is slower. Still, under most circumstances bracketing would be adviseable if you aren't sure you have the exposure dialed in.

[Volatile]

2. I was using f5.6 to try to put some bokeh on the bush that was a foot or so behind them, but should I have been stopped down to f8 or f11 or more?


no, you should go the other way, lower number = more blur

I was asking if I should have sacrificed background blur for a smaller aperature in order to avoid overexposure of the highlights.

Since I still am not good at picking manual settings out of thin air, I think I will shoot Av mode, chimp and read histogram, then use those settings as a starting point for adjustment. I hope that's not considered cheating...

[benyl]

Maybe my logic is flawed, but I always try to shoot at the largest aperture possible for the given amount of light. Remember that a quick shutter speed also helps to shrink the depth of field.

[dtrayers]

Maybe my logic is flawed, but I always try to shoot at the largest aperture possible for the given amount of light. Remember that a quick shutter speed also helps to shrink the depth of field.

The shutter speed has nothing to do with the DOF. DOF is controlled by the lens aperture and the focal lenth. It just so happens that at larger apertures you tend to have faster shutter speeds, but that's because the camera it trying to maintain a consistant exposure value.

[Roger_Cavanagh]

Maybe my logic is flawed, but I always try to shoot at the largest aperture possible for the given amount of light. Remember that a quick shutter speed also helps to shrink the depth of field.

The shutter speed has nothing to do with the DOF. DOF is controlled by the lens aperture and the focal lenth. It just so happens that at larger apertures you tend to have faster shutter speeds, but that's because the camera it trying to maintain a consistant exposure value.

In addition to what Dave has said, making decisions about controlling DOF using different apertures is part of the creative process. Large apertures (low numbers) mean less DOF and more separation of the sbject from the background, which is desirable in some situations, e.g., portraits, but not in others, e.g., landscapes. close-ups.

But Tv can be a good mode if you are "rushing about" - narrow DOF is usually better than blurry pictures. :)

Regards,

[touchup]

I have an s45 with minimal camera experience. What I am wondering is, how did you guys tell how well pictures were exposed when using non digital cameras? I have never used or seen any slr cameras, digital or film, so please pardon me if the answer is very basic! Do film slr's have histograms??

Adam

[dtrayers]

Get to know your meter (in camera or otherwise), meter different parts of the scene, and bracket!

Here's a link about it: http://www.camera.canon.com.my/archive/photography/art/art2/metering.htm

And here's an excellent exposure exercise whether shooting digital or film:

http://www.vividlight.com/articles/802.htm