Newbie Aperture Question

[NateNLogansDad]

This may be a stupid question but I know it'll probably have a complicated answer.

Hypothetically, if you had 2 lenses made by the same company both fixed at say 35mm but one was a 1.8 and the other was 2.8, would you get the same quality if you set your camera to 2.8 for both?

[Chikabowa]

Not necessarily.
There can be massive differences in quality of the glass inside the lens, the focus mechanisms, sharpness, etc. They both will, obviously, give you a f2.8 aperture, but depending on the make and quality of the lens itself, you may or may not notice other issues between the two side-by-side comparisons.

If you shoot Canon, take a 50mm lens and try the same shot out with the 50mm, f1.8, the 50mm f1.4 and then the 50mm f1.2L. You'll notice a ton of difference I'm sure. And that is based on the fact that the 50mm f1.2L uses more quality glass, has a sturdier build, and has razor-sharp focus. It's a $1200 vs. the 50mm f1.8 that is ~$100. There is a reason for that extra cost! :)

[GrillMouster]

Ditto what Chikabowa said. When it comes to exposure, both lenses will transmit the same amount of light to the sensor if they're both set to the same aperture and they both will have the same depth of field at that aperture if everything else is the same (same camera sensor size, same distance to subject, same focal length, etc.). However, they the sharpness/clarity and contrast of the image may be different, because of other factors. lenses tend to be at their sharpest a few stops down from their maximum aperture. So, the lens that opens up to 1.8 may be sharper at 2.8 than the lens with a max aperture of 2.8 would be. The quality of the glass elements, the number of glass elements, optical coatings, build quality, etc.. may be different between lenses and those can have an effect on the image.

So, in terms of overall exposure, no difference. In terms of image quality, possible difference. Will you notice the difference in image quality? Hard to say without looking at actual samples from both lenses. You might wanna check out image samples by doing google searches. Also, on some image sharing sites, like Flickr, you can do searches by specific equipment to see images with those lenses.

[disneyboy2003]

Here's a thread that might provide some additional answers:

http://www.disboards.com/showthread.php?t=2312562

[Kevitivity]

This may be a stupid question but I know it'll probably have a complicated answer.

Hypothetically, if you had 2 lenses made by the same company both fixed at say 35mm but one was a 1.8 and the other was 2.8, would you get the same quality if you set your camera to 2.8 for both?

Assuming the glass is the same in both lenses..

Most would prefer the lens with the 1.8 aperture. A wider aperture means more light gets through, allowing you to use a higher shutter speed or a lower ISO.

But the complete answer is really more complicated. I highly recommend this book...
http://www.amazon.com/Digital-Photography-Book-Scott-Kelby/dp/032147404X/ref=sr_1_3?ie=UTF8&s=books&qid=1261473376&sr=8-3