question about the canon 18-55 kit lens

robertwsimpson · Aug 14, 2009

Do you guys who have this lens think that it's pretty much always just a tad bit out of focus? It just seems like I can never get a perfectly sharp picture with this lens no matter how hard I try. Wondering if I'm the only one. I get great pics with my 55-250 lens, but it has IS and maybe better glass? I dunno. Maybe I just got a dud.

bigtwinky · Aug 14, 2009

Can you post up a picture of what you feel you should of had perfect focus on, and include the camera settings and info on the location (lighting and such)?

robertwsimpson · Aug 14, 2009

ok I shot 6 pictures... 3 at the widest aperture, 3 at the smallest, and the wide ones seem much sharper... I don't know if that's because of the faster shutter speed or what, but it's very noticeable, and I see the same thing even when I'm using a tripod.

All pictures are 100% crops taken at ISO 100, shutter speed, aperture, and focal length listed before each picture.

1/2000
5.6
55

1/3200
3.5
18

1/3200
4.5
31

1/80
29
31

1/60
29
55

1/100
22
18

Josh66 · Aug 14, 2009

Try some around f/8-11. That's usually the "sweet spot" - after that, you're going to start getting some diffraction (which will cause it to lose sharpness).

double5 · Aug 14, 2009

which focus point was selected?

robertwsimpson · Aug 14, 2009

these are giant crops from pictures centered on the hydrant. I just wanted to include a deeper field for reference. The label should be in focus in every photo.

by "after that" do you mean higher or lower aperture value?

Josh66 · Aug 14, 2009

robertwsimpson said:
by "after that" do you mean higher or lower aperture value?

Smaller aperture, which is a higher f/#.

KmH · Aug 14, 2009

Check out the image posting sticky at the top of the the Beginners Forum page. They'd like you to resize your images to no more than 800 pixels on the long side before you post them. It saves bandwidth.

robertwsimpson · Aug 14, 2009

KmH said:
Check out the image posting sticky at the top of the the Beginners Forum page. They'd like you to resize your images to no more than 800 pixels on the long side before you post them. It saves bandwidth.

unless TPF takes my pictures and re-hosts them, it affects my photobucket bandwidth, not TPF bandwidth. These were posted at full resolution for a very good reason.

I just went out and took some f8 pictures and they turned out pretty well. I didn't know that shooting at a smaller aperture had that effect. I used to always shoot with a small aperture for whatever reason, so that makes sense that all my pictures were blurry. mystery solved!

robertwsimpson · Aug 14, 2009

The maximum size should be no more than 800 pixels wide, and 600 pixels high, in order for it to fit on most screens without having to scroll.

lol it doesn't say anything about bandwidth.

and since the forum automatically resizes images that are too large to see all at once... no harm no foul.

Josh66 · Aug 14, 2009

robertwsimpson said:
The maximum size should be no more than 800 pixels wide, and 600 pixels high, in order for it to fit on most screens without having to scroll.

Click to expand...

lol it doesn't say anything about bandwidth.

and since the forum automatically resizes images that are too large to see all at once... no harm no foul.

And you can customize that too. I forget how mine is set up... But it only resizes images that don't fit on my monitor without scrolling, whatever those dimensions are. I used the "2d ruler" widget for Opera to measure it.

Now - back to the topic.

You said that they were all 100% crops... If you start looking at everything at 100%, you won't be impressed easily. Even a 'sharp' photo won't look tack sharp at 100%.

UUilliam · Aug 14, 2009

Plus your most likely shooting wit ha 1.6x crop sensor, what I tend to do when resizing my images is Long side / 1.6 = new long side (but resize in photoshop so the short side is resized by the same amount)

This generally makes my image a tad sharper as it removes the x1.6 Magnification that the sensor causes (and I take it to be the 1.6x is a digital zoom?)

musicaleCA · Aug 14, 2009

The thing is that if you have GIGANTIC pictures, it will be unbearably slow on slower connections (thankfully for the last few months I've been on a university network that is blazingly fast), but worse is that it can wreak havoc with browsers. FF3 chokes a bit and can't scroll smoothly if it has to display 2000 pixel wide images. (Yours get close to that limit; it only skips a little.)

Ditto on what O|||||||O said. It's difficult to be happy when you're pixel peeping all the time. When the problems become an issue at the size you're going to be viewing at, THEN you've got to take care of it. (The quality of the glass plays a huge role in this. In fact, my 50mm f/1.4, which isn't L glass, is sharper at f/2.8 than my 24-70mm L. Go figure.)

Take a look at the MTF tables here. Your 18-55 is sharpest at 35mm at f/5.6. At 18mm it's best at f/8 (note how the borders really suffer here at f/5.6). At 55mm it's pretty soft all around, performing best at f/11. Not the sharpest lens in the world; knowing where it performs best and where it falters will really help you improve the quality of your images. (I've been printing out these tables for all my lenses and carry them with me as a reference.)