Camera Lenses and Vignetting

[Radar]

I'm thinking that longer focal length (or slower) camera lenses have less vignetting than camera lenses that are say widefield? Can anyone add to this?

[Tenacious Del]

Obviously I'm not an expert, but it sounds right. Widefield takes images at an increased angle, so it is feasible that this causes more vignetting.

[AstroTasmania]

This is not really a problem related to focal length, it is the quality of the lens design/manufacture. Suffered mainly by most low cost lenses because they are made to very minimum specs. Put two lenses of the same focal length side by side, one costing $200 and the other $2K, one will and one won't. However, in the low cost lens the effect will be more pronounced in the wider angle lenses say 50mm. It is one of the reasons that all high quality lenses generally cost so much more.

Clear skies...

[Radar]

I know this next question is a long shot, but is there a way to tell by looking at a lens if it has cheap lenses or a possible vignetting problem?

[Craig]

I know this next question is a long shot, but is there a way to tell by looking at a lens if it has cheap lenses or a possible vignetting problem?

In short I beleive the answer is no. If however "you have depth of field preview on your camera you can test by looking at a uniform light such as day sky or white paper you can see if vignetting occurs."
Grimms Pgotography.

I've tried this but my lenses are fine so not sure how effective it is.
It is also a good test to take the photo of white sheet against another white sheet or wall to ascertain how sharp lense is. If you can't pick out line clearly across whole length or if uneven you can do better.
Hope that helps.

[Radar]

Interesting stuff Craig. Thanks, I'll check it out.

[AstroTasmania]

Here is a link which very nicely explains all you need to know about this topic. It is in plain simple language with diagrams.

In general terms, these problems are overcome by making lenses larger than they need to be, hence much much higher costs. A compound camera lens has multiple lenses, however, we refer to it as a lens. (not lense)

In astrophotography the effect is seen more often because the lens is often used wide open. Stopping down the lens reduces the effect. As I have mentioned previously, a 50mm lens costing say $150 will not compare with a 50mm lens costing $500, which will be sharp and fully illuminated at maximum aperture.

If the diagonal in a Newtonian is too small it will not fully illuminate the field it is supposed to and fall off of light at the corners of the film frame will be noticeable.

Hope this helps,

http://www.vanwalree.com/optics/vignetting.html

Clear skies & fully illuminated optics.