Groups and Elements

jamism

so i know what groupes and elements are, but what do more groups and elemnts do vs. fewer. and when dose many groups/elements become to much? thanks.

ian408

Are you talking about how lenses are made?

pathfinder

Th simple answer is that simple lenses - two surfaces only - front and back cannot be be in focus for all colors - They will suffer from badly chromatic aberration.

Prime lenses are generally sharper and have higher contrast than zoom lenses, and they TEND to have fewer elements and groups than zooms. Prime lenses are usually simpler than zooms, which results in fewer reflecting and refracting surfaces inside the lens to scatter and reflect light. Hence, their better image quality.

Zooms usually have more elements and groups to allow color correction across the range of focal lengths of the zoom. This usually requires more elements and groups than prime lenses. ANd more internal reflecting, refracting and scattering, and hence, lower contrast and sharpness.

However, lenses should NOT be evaluated by the number of elements and groups, anymore than physical fitness can be evaluated by someone's weight in pounds ( unless you know their height, weight, age, sex, training, etc)

Some rather simple lenses are used in view cameras with stunning results with only a 2 or 3 elements and no groups, like the Cooke triplet.

To evaluate lenses, it is better practice to read reviews and posters opinions, and then take a grain of salt with them too. Some posters feel their is significant variation between the same lenses of the same design whether made by Sigma, Canon, Nikon, Tamron, etc.

My personal feeling is that most PRO lenses are pretty good if used properly. Primes are usually better than zooms, but PRO zooms are very good. I see more images with poor quality due to uses error than lens quality issues. No tripod, poor focus, way too slow a shutter speed, etc.

I do not expect a 28-200mm f4.5-6.3 lens to be a great optical device, but rather a convenient lens for a tourist. I had a 28-200mm Tamron lens, and it did suffer badly form chromatic aberation as I expected. Still, I got many very nice shots with it, it used appropriately.