Nothing like jumping right in! (focusing question)


TPF Noob!
Nov 27, 2007
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Hello everyone

Newbie here! and I'm not shy, I have a question right away.

I have a 30D, and a Canon prime lens. 35mm 1.4L. It's a really great lens. Sometimes I wonder though if there is a focusing issue and I don't know if it is me, or maybe it needs to be calibrated.

The photos are tack sharp in bright daylight. amazingly tack sharp. love it!
In dimmer light, they aren't always tack sharp and in fact I'm sometimes not sure WHERE it focused. It really doesn't look focused at any point on the photo. Or if focused, it's still kind of a soft focus. Not tack sharp.

I also know how to change the focusing point on a 30D, there is a button that will give you a choice of where to make the focus point and when the camera doesn't seem to be focusing where I want it, I change that so that it forces it to pick the spot I want. It still doesn't always seem to be focusing where I want though. Maybe I'm not looking hard enough at the resulting photo though.

Here is my method: I am almost always handheld. I only have a tiny tripod and rarely is it convenient to set it up anywhere outside. So, I set the shutter speed on 1/50 and let the camera sort out what aperture is optimal. Due to the dim light, it therefore will select a larger aperture which affects DOF. i.e. it may be 2.8, or 3.5, etc. If the lighting is better then of course it will pick a higher aperture which is a better DOF.

what else can I do, if I would prefer to "travel light"? How can you tell if the lens need to be calibrated? Is there something I am doing wrong, other than the tripod issue?

I also rarely change my ISO above 100 because I know higher numbers give noise. bad idea?

many thanks.
I think the issue might be shallow depth of field at wide apertures. As the light level dimishes your camera selects a wider aperture for a given shutter speed. You understand this. DOF also dimishes at closer focusing distances.
Id say its a combination or no tripod and your iso, with a 30d or any newer dslr really, your ok raising the iso. Even at 800 noise shouldnt be a huge issue, but 400 you would notice almost no difference, dont be afraid to raise that iso a bit, after all thats one of the great advantages to digital is you can raise the iso so the image is able to be taken while hand held, or maybe look into a monopod, there a lot smaller, and they even make ones that are basically a gun handle that you press and it extends immediatly, much more convenient and it helps to lower hand shake.
thank you - I will try that higher ISO!

Would you recommend that I just force a smaller aperture, take a darker photo, and then fix it later in Picasa or photoshop (once I learn photoshop!)
Oh and about that 1.4 lens, yes 1.4 aperture will give you virtually no depth of field. And no i dont reccomend forcing a smaller aperture, after all theres only so much you can bring back in photoshop, when it hits a certain point its gone. The iso will also help with the aperture issue i believe, raise the iso and you can use a smaller aperture so that would alleviate that problem as well . :)
most lenses have trouble focusing in the dark. If you want, you could use a focus light or something (a flashlight) but that'd throw off your metering if you don't do it properly...

Use the center focus point only, and then you won't have to worry about which point is working. You just focus on the center and then move the frame after it's locked.

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