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smaller aperture better IQ?
Reading comments on lenses (which I'm looking to purchase), people mention often when talking about the 350/400d kit lens) that you get better IQ when taking it a few stops down to f8 for example. does that mean the smaller the apature ,the better IQ you can get?.

I normally shoot with a wide open aperure, and havent been too pleased with the quality of my photos so far....

Comments (6)

DanGB wrote:.

Does that mean the smaller the apature ,the better IQ you can get?.

No. Stop down too far (and how far that is depends somewhat on the lens) then the IQ suffers again..

I normally shoot with a wide open aperure, and havent been toopleased with the quality of my photos so far...

What quallity have you not been pleased with? Post a few samples?.

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #1

Thanks..

Its probably the fact I'm a beginner with SLR's so havent got the settings right yet. i'll post pics if I get the time...

Comment #2

Depends on the lens, and what you mean by IQ..

Almost all lenses have a sweet spot somwhere in their aperture range. Either end of the spectrum will introduce problems, albeit different ones. Unfortunately you can't just assume that it's right in the middle either. The lens has to be tested to see where it's best performance comes..

Remember though that everything is a trade off. As an example, say your lens' particular problem is vignetting (darkness in the corners) at large apertures. Stopping down some will most likely help that problem, but you'll also be increasing the depth of field in the resulting image. You'll also have to use a slower shutter speed which can result in motion blur depending on you and the subject. Which one of these things is worse depends on the composition of the shot. Maybe you could zoom out (or step back) and crop out the vignetting instead, but now you're losing resolution.



If you could post a sample or two I bet the group could give you some more specifics on what your options are...

Comment #3

By the way, the Lens I am using is the 18-55mm f3.5-5.6 kit lens you get with the Canon 400D...

Comment #4

DanGB wrote:.

By the way, the Lens I am using is the 18-55mm f3.5-5.6 kit lens youget with the Canon 400D..

According to testing, at 18mm it's sharpest at f/11, at 35mm and 55mm it's about the same f/5.6 through f/11, although vignetting is an issue at apertures wider than f/8..

Http://www.photozone.de/8Reviews/lenses/canon_1855_3556/index.htm.

Seen in a fortune cookie:Fear is the darkroom where negatives are developed..

Comment #5

Short answer : No..

Long Answer : ( and very generalized ).

Very generally most lenses work less well at and near their extreme settings..

This means that at the very wide and very long ends of a zoom, for example, the image is less sharp, more distorted and may have vignetting and other issues. Somewhere in the middle there is usually a peak sharpness..

Likewise with aperture. At very wide apertures lenses are ( often but not always ) "softer". There is more distortion and CA and vignetting. As you move down a stop or two you get an improvement..

However above f11 the effects of diffraction degrade image quality a lot. f16 is really too high for most lenses..

Note also that the quality of image is different across image. Corners and borders tend to more affected by softness and so on..

Prime lenses are (generally) designed to be more optically precise over a larger range of settings..

StephenG.

Pentax K100DFuji S5200Fuji E900PCLinuxOS..

Comment #6

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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