Lens/aperture/sharpness question

The lens I have is a Canon kit lens. I know I need prime lenses. But I need to ask a question about the lens I have now. It seems to me that no matter what aperture I use, when I have the opportunity to use multiple apertures for the same shot, the f/9 shots are always, without exception, the sharpest. For a cheap lens, is it possible that there is an aperture at which a particular lens produces the sharpest images? Or is there something about f/9 that must be working better for me than other apertures, smaller or larger, because of something about my own technique? Have you ever heard of anything like this? Thank you for any insight.

All lenses have an optimal aperture with regards to sharpness. Typically that aperture is between f/8 and f/11.

For any lens, inexpensive or otherwise, there is always a "sharpest" aperture. It varies with every lens but, "generally", the sharpest apertures are those where the lens is stopped down a few stops - f/8 to f/11 or so. Keep in mind, that is a GENERALIZATION, and your mileage may vary. I test each of my lenses when I purchase them to find out which apertures are sharpest and which are least sharp.

Every lens has its "sweet spot" aperture in which it is sharpest. The specific aperture will differ based on optical design and the effects of diffraction. Most lenses offer their best performance between f/8-f/11.
And no, you don't necessarily need prime lenses. You need lenses that can resolve sufficient detail to match your sensor's capabilities. Even if a given prime can resolve somewhat more detail than a given zoom, if the sensor is not able to distinguish the difference, it is a moot point.

Guy

I used to have many prime lenses when I did film work Barbara (1972 - 2000) but that was then. These days, optics on zooms have improved greatly. I only own one special purpose prime today (a 24mm tilt shift lens). In general, I use between f/8 - f/11 which works well but it depends what you are trying to achieve. I have used f/16 - 32 or f/4 to 5.6 (Macro mostly) in special situations depending on the lens and effect I want to achieve. My advice is to look at reviews of your particular lenses to see where they work best and how that info fits what effect you are trying to achieve or better yet, experiment to get the effect you want. http://www.the-digital-picture.com/Reviews/Canon-Lens-Reviews.aspx is a good start. There are other place for lens reviews as well.

Hi Barbara, whether or not you need a prime lens depends a lot on what you want to shoot. For landscape photography it is common to use zooms in the 16-200mm range. I find that in the wildlife/avian area, it seems that most people seem to use prime telephoto lenses such as the 300mm, 400mm, 500mm, 600mm and 800mm lenses. Landscape and avian/wildlife photography have very different requirements. But that is not to say you can't use a prime in the short range or a zoom in the telephoto range.

I also agree that you don't "need" so-called prime lenses. Modern zooms are excellent. As others have mentioned above, at f8 pretty much all lenses are going to be equally sharp. A true story. Last summer I was taking shots at Dettifoss (largest waterfall in Iceland.) I pulled my 77mm B+W mrc polarizer out of my pocket so I could place it on my Nikon 17-55mm f2.8 lens but it got away from me. It took one short hop and disappeared into the abyss. I was too terrified to even consider making a lunge for it! I love polarizers and use them around virtually all daytime shots with water in them, and Iceland is all about shots with water in them. I put my lens away and pulled out my back up lens, a Nikon 18-55mm VR, and screwed on the 52mm polarizer and kept shooting. My choice was to continue using the Nikon 17-55mm f2.8 without a polarizer for the rest of the trip, or use the 18-55mm VR with a polarizer. I went with the latter. I was mostly shooting during the day, at f8-f11. When I got home I closely examined my shots and just as I suspected, there was no difference between sharpness from the $100 lens and the $1,000 lens.


Kent in SD

Barbara,
I use the same lens, and find that f8-9 gives the best results. I also find that I need to be very certain where I am focusing. If you can find a copy the Spring 2011 issue of PhotoPlus Canon Edition out of England has a test report on 10 lenses in this catagory, rating the 55-250 best value.

Barbara... I echo many of these comments and sometimes,timts there are actually a few acceptable "kit" lenses. I tell my workshop attendees... Look what the pro's use, We use these lenses for a reason. If you can not afford these lenses, as lots of folks can't find the best lenses, as close to the quality these lenses( that the pro's use) and buy them. I know many folks who acquired some used "pro" lenses, used... as well. I would highly recommend KEH for used gear. You might save a good amount of money by buying a used "Pro" lens. For example (I'll use Nikon as I am a Nikon guy)... a new Nikon 24-70 2.8 is a "10" on a 1-10 scale. The previous 28-70 2.8 is , I would say a 8-8.5 vs the newer 24-70mm lens,... on a 1-10 scale. You can pick up the later for about $700-1000.00 less. Yes you sacrifice 10mm and a slight bit of quality( most cases hard to detect) but might save 1000.00 for GREAT glass. The same goes for Canon.
Good luck!............... and I love the last nane!

Jack Graham ( no relation ... I think?)