Chris help new canon lense

[chris-p]

Yeah, the longer the focal length, the more perspective compression you get and there's no marked difference between either of my primes and a zoom lens at the same focal lengths (with the same apertures).

[cosmicma]

thanks for clearing that up
thought i would mention it anyway not knowing if it was an issue or not

[Cutter]

Originally Posted by chris-p

Hmm, looks fine to me... dunno what anyone else thinks??????

It's pretty sharp from front to back. If anything, it looks sharper at 100% than at 50% (which is what my screen fits it to). It certainly doesn't seem any worse than the Sigma 10-20mm on my D90. In fact the only thing I can see thats technically wrong is the CA against the sky!

Did you shoot in RAW or JPEG (EXIF doesn't tell you that - or if it does, I don't know where)?

Yes chris I shot in Raw then converted to Jpeg. You say the photo is fine and sharp could my problem be that I zoom in to much when viewing? at what magnification should you assess a photo ?

A big thankyou for all the info

[chris-p]

Originally Posted by Cutter

Yes chris I shot in Raw then converted to Jpeg. You say the photo is fine and sharp could my problem be that I zoom in to much when viewing? at what magnification should you assess a photo ?

This is tough to answer actually...

I viewed the photo I saved at 100% and it looks fine. Zoom in any more than that and you're going too far to assess the quality. The problem is that at zoom levels of more than 100% you've got to remember that you're going to start to see the "gaps" (for want of a better word) between the photodiodes on the sensor. 100% is the images native size, so always assess this sort of thing at 100% or less.

The other thing is, the photo I've downloaded from above has an image size of 2500 x 1667 pixels, which is about half the size of a RAW file from a 50D. Also, it's been converted to jpeg, which will have sharpened the image.

At what sort of zoom level are you looking at the shot and deciding the focus is off?

[Cutter]

Qoute At what sort of zoom level are you looking at the shot and deciding the focus is off?

it was 17mm and the focus was 1 third up, is that the correct focus for lanscapes ?

[chris-p]

Sorry Mark, I meant zoom % in PS

A third into the frame is a good rough guide. If you're worried about DoF then get a hyperfocal distance chart - that way you always know it's right. If you have a smart phone of some sorts there are apps you can use that calculate it for you.

[Cutter]

Originally Posted by chris-p

Sorry Mark, I meant zoom % in PS

A third into the frame is a good rough guide. If you're worried about DoF then get a hyperfocal distance chart - that way you always know it's right. If you have a smart phone of some sorts there are apps you can use that calculate it for you.

I do go beyond 100 perhaps 200 %

[chris-p]

Originally Posted by Cutter

I do go beyond 100 perhaps 200 %

The problem with that is you're then asking the computer to show you the image physically larger than it really is. This causes horrible artefacts and jagged edges as whatever software you use has to interpolate the image up. This is an example (click for bigger so you can see it properly):



These are crops from my screen using the image you posted earlier (which is already around half the size of the original file). I've specifically picked an area at the rear of the photo so that it's away from the actual point of focus.
At 100%, considering the short focal length, the depth of field is pretty good and the image looks pretty sharp. As soon as you get above 100% it starts to look soft and at 300% you can really see the "jaggies". But, considering how far away from the point of focus this is, and considering the focal length being fairly (and not very) short, at 100% I don't think it's that bad. A quick bash with the unsharp mask or a high pass filter and it'd be fine.

And anyway, who is ever going to look that closely at it or print it that large?!

[Cutter]

Hey thanks chris that explains alot . Again thanks for taking the time to explain another piece in my puzzle