Digikurage wrote:.

I would like to understand when do you need a fixed focal length lenseg. a 40mm, when there are 14-50mm available ? Thank you..

You wil never *need* it, but the advantages of fixed (or prime) lenses are that the lack of zoom mechanics in the lens generally means better image quality, and (more importantly) they are usually faster, i.e. their maximum aperture is wider, often f/1.8 or 1.4, which zooms cannot match. This is crucial for low light shooting for example..

Alex..

It's easier to design and build a practical fast lens if it's for a single focal length. Even the priciest zooms in the normal range tend to be no faster than f/2 or (more commonly) f/2.8, and those can get fairly pricey; compare a Canon EF 24-70mm f/2.8L USM. If you just want to shoot shallow DOF shots at 50mm with the Canon EF system, the 50mm f/1.4 is probably a far better buy (the f/1.2 is not cheap, 'tho). Smaller, cheaper, lighter, faster..

Brighter viewfinder this way, too, since the view is prior to stopping-down unless you're using an old lens or an adapter that forces stop-down operation...

Digikurage wrote:.

I would like to understand when do you need a fixed focal length lenseg. a 40mm, when there are 14-50mm available ? Thank you..

Fixed focal length lenses can be made BETTER performers, the design being optimised without the compromises necessary in a zoom. Indeed, some people specifically choose to use "prime lenses" [fixed focal length lenses] exclusively. They might enjoy....

I) Wider maximum apertureii) Higher definition at all aperturesiii) Less pincushion or barrel distortion.

Iv) or an alternate trade off between benefits listed above, including and in addition to a lower price than a [less well performing?] zoom.Regards,Baz..

There is also an emotional component involved. I use some old AIS prime lenses because they are of superior materials and feel smooth and well damped during focusing. If you handle some of these old lenses, you will understand. My 105mm F2.5 is probably my sharpest lens, and I have plenty of modern lenses...

The choice between zoom and fix focals is very much an individual need issue. For a start, todays zoom is quite good and all of them do a decent work, Read that decent, not quality. While fix focals of similar vintage or even older ones usually put them to shame especially when used at those wide open speed..

There is of course disadvantage to a fix focals. Namely the inability to varies framing from a fixed position. To some this might be handicapped enough. To others, it's not a problem..

Me myself, I always prefer fix focals over zoom. The quality gain and the extra speed open up imaging potential that is not possible with the zoom and I really prefer the more compact size and lighter setup. Inability to frame is not a issue with me as I am not out to machine gun everything ....

In the end, one must decide if one need or prefer which type of lens for a specific need and specific occassion. Franka -..

Thank you so much guys. I am new to photography, currently using just a Panasonic FX9, but lately became interested in the DSLR world, so much to learn  But this site is so nice, full of experienced people who are willing to come to the beginner's forum to share your knowledge with novice like me, really appreciate .

I don't have a DSLR yet and most likely won't get a fixed focal length lens, but I just want to understand why people would go for that, I knew there must be a reason...

Fixed focal length lenses (primes) are also very good at avoiding lens flare...

I can understand. A lot of people just think of range and why bother with a fixed focal length? I found fixed focal length lenses are not only smaller and sometimes faster, but can give a much better photo quality. It does go beyond sharpness/resolution. A fixed focal length may have better bokeh (a smoother look to the out of focus areas) and better capture the smaller differences in color and contrast...

So much about image quality..

I prefer the feel of the smaller, lighter fixed-focal length ("prime") lenses, AND when I make myself leave the zoom lens at home, I compose better, because I'm not constantly changing my angle of view!.

You will think about your photos more. It's a sort of "basics" approach to photography. This topic is common, and people like to point out that some of the best photographers ever used just one or two focal lengths..

There's no question that a zoom is handy, but it just takes a few minutes to say, ah, I need to get a wider shot here. Let me unscrew this one, and put on my wide-angle prime, or step back!..

Clint Sanders wrote:.

Fixed focal length lenses (primes) are also very good at avoidinglens flare..

Primes have fewer elements than zooms; they don't need so many. Even with today's coating technology, each lens surface adds stray light and reduces the contrast. Since there are fewer curved surfaces inside the lens, there is less opportunity for flare..

Tom Rogers' 105 f/2.5 Nikkor, his (and my) sharpest lens, has only 5 elements. Zooms tend to have 10 to 15 elements. This has, in my opinion, a significant effect on the appearance of a picture. The 105 is so crisp, it's too harsh for portraits. Most people don't look good enough for this lens. I have pictures of cats where you can cut yourself on the whiskers...

Not always a problem but definitely an effect..

Leonard Migliore..

Zooms tend to have very small apertures at the narrow end, unless you buy one of the super grade ones that are (say) f/2 throughout, but look at the price of them. Then look at the price of a prime tele with f/2 available..

Regards, David..