Focusing problems w/a Digital XT

[monique_evette]

I just switched to digital and decided to invest in a Digital Rebel XT. My main lens is a Canon EF 28-105 (F3.5). I also used this lens on my Canon A2 film camera.

I'm having a focusing problem and since I have never had it with my Canon A2 I am thinking that it’s the Rebel.

I have been shooting weddings and when it comes to group or single body shots I am failing at producing a sharp image. My focusing light says everything is in focus, but when I upload my pictures to Photoshop and zoom in at 100% the picture is blurred (some worse than others) and I find myself having to use unsharp mask on almost EVERY PICTURE. However if I zoom in real close just for headshot the camera seems to do fine. It’s just when I back away to do fully length body shots. Even when I have to be quick to get a candid shot. There was one that I actually made sure to focus in on the bride and then zoom out so I would be sure to get a clear shot of her tossing the bouquet, and it would have been absolutely adorable since she look right at the camera a soon as she did it. I thought I got it, which I did, but she was all out of focus. Really really frustrating.

I know the Rebel has a hard time focusing in dim lighting but this is getting ridiculous. I though maybe I wasn't paying attention to my shutter speed, but everything has been shot at 1/60 of a second or faster. And I usually shoot at my largeest aperture of 3.5 to 4.5. I also use a flash and lately with a bounce card.

So can anyone give me any suggestions or at least let me know if they are having the same problems?

[kenw]

couple of things, just slightly educated guesses:

1/60? I assume a tripod was used? If not, there's a big part of the problem. people need a bottom end of 1/125s or better imho. On the shots you used a flash with, what sync speed did you use? I'm guessing something a bit faster than 1/60?

Zooming after focusing will in most cases un-focus the lens. Some lenses WILL stay focused while zooming, but I don't think that lens is one of them.

Max aperture is most likely the biggest culprit as the focal depth is going to be on order of inches or less. Depending on what the exact focus spot was, more of the pic willl be out of the focal point than in it.

Your Rebel allows you to select various focus/metering points, which one did you use? Was it on the nose of the subject or on the wall behind them? If you use the center spot and take a lot of couples' pics, it will invariably focus on the wall behind them. The camera will tell you it IS focused, hence the light, but on the wall or whatever. Individual body shots being OOF is a bit harder to understand (or to SWAG at.....) unless the aperture is causing the shoulders to focus and the face, at more than a few inches difference in focal point is too far to work.

[monique_evette]

I was taught that a tripod is used once you start getting closer to 1/30th of a second. Anything faster can usually be hand held. I guess not... but I seriously used that rule for my film camera with the same lens and have never had a problem. The flash sync I use is whatever the camera and the flash decides. I have no understanding about how to use my flash manually. I just put it in AV mode and choose my aperture and allow the flash to compensate. It even compensates if the camera is in manual mode as well, so I have never really bothered with really understanding how to use my flash in manual mode.

Ok so even if I keep the same exposure when I zoom in to focus on the eyes and then zoom out it can loose focus? I know that I did that with some group shots and was able to produce some clear pictures, but not in others.

Further, I have been forced to use an ISO of 800 because of bad lighting and with that I couldn't shoot with a faster shutter speed of 1/60. I didn't want to go to 1600 since the Rebel XT already has an issue of producing a lot of noise with an ISO of 800.

Finally I try to focus on the eyes of the subject with anything I shoot. Again outside shots are not a problem, I guess cause there is more light and I can use a faster shutter speed, its just indoors that has really been making me scratch my head.

Another question, I have noticed that the Rebel XT does not compensate its exposure for ISO speeds. My Canon A2 always made the exposure adjustments when shooting inside or outside rather it is with flash or not. However the Rebel XT will over expose or produce a really really bright picture if I go from shooting 800 inside to shooting 800 outside on a bright and sunny day. Why am I shooting 800 on a bright sunny day with flash, well... I didn't have time to adjust my ISO or think about it since it was brief moment that I tried to capture (and failed).

[AndrewCCM]

Something to keep in mind too.. 100% viewing on monitor is not what a print looks like. If you're used to getting film scanned, that could be what you're seeing.. But.. Just throwing that out there.. It very well could be a problem. Is it blurry or just a little soft? Many times, digital can show flaws in substandard glass too..

[NathanJK]

As for the outside bit, if your at 800iso and shooting at f3.5 or so, I could see you possibly exceeding the maximum shutter speed of your camera. I'm not certain, but maybe in full sun. Then it would overexpose. My suggestion...try not to forget

[kenw]

the 1/mm rule is applicable to digital and film and has to do with handshake blur. As a general rule, the shutter speed should be faster than 1/mm, so a 100mm shot should be faster than 1/100s. IS lenses can help lower the needed shutter speed but only by a little bit.

For the ISO issue, does it have an "Auto" ISO mode? that may help.

[monique_evette]

Originally Posted by kenw

the 1/mm rule is applicable to digital and film and has to do with handshake blur. As a general rule, the shutter speed should be faster than 1/mm, so a 100mm shot should be faster than 1/100s. IS lenses can help lower the needed shutter speed but only by a little bit.

For the ISO issue, does it have an "Auto" ISO mode? that may help.

Are you talking about the distance? So if the distance is 100mm than I would need a shutter speed faster than 1/100s?

[crazeazn]

Originally Posted by monique_evette

Are you talking about the distance? So if the distance is 100mm than I would need a shutter speed faster than 1/100s?

yes its always 1/x, x being the focal length

[kenw]

not the distance to the subject, but the focal length of the lens, sorry i was unclear.

A 100mm lens should be used at 1/100s or faster.

A 28-105 zoom lens at 28mm should be used at 1/28 or faster and at 105 it should be used at 1/105s or faster.

[monique_evette]

Oh ok, gottcha. I will keep that in mind. Thanks guys you all are soo helpful.