whats the benefit??

[Ms Monny]

Hi all

This is a real amateur question I am about to post....

What is the benefit of having a fixed lens like the 'nifty fifty' 50mm, or the 135mm lens? Is it because they are fast with a large aperature?? Doesn't it make the lens less useful and versatile?

Love to know your ideas on this.

cheers
MM

[andylo]

In my understanding they are usually:

Faster/Larger Av
Sharper
A lot lighter (less glass)
In some cases - provide a little more creativity (larger Av = shallow DoF = better Bokeh)
Cheaper

I have both the 24-70 zoom and a 50 1.4 fix focal.... when I go out at night, the 50 1.4 is usually the one on the body if I don't want to use flashlight.

[Ms Monny]

hmm, I guess the 1.4 is pretty sharp! I am thinking of buying a good lens and was wondering why so many go for a fixed lens. Nifty fifty seems to be on alot of people list.

What about composing the shot? I guess it just means walking up and back to get the right frame!!

[PH005]

Less moving parts = less likelyhood of trouble.

[Kym]

Lens design and construction is a physics and engineering compromise.

Zoom gives flexibility at the loss of IQ and aperture. The IQ loss is quite small on expensive lenses (top range L in the case of Canon).

By not having as many moving parts or optical compromise a prime is generally faster, lighter and cheaper than a zoom lens.

All lenses have a sweet spot which is usually at a particular zoom and aperture.
Typically 2-3 stops down from wide open in terms of aperture, often at around f/8.
On a zoom the sweet spot is somewhere in the zoom range.
My 50-500 is best at around 440mm and f/8.

Prime lenses usually have less lens elements and groups for a whole bunch of technical/optical reasons which means less stuff between the sensor and the subject, hence better IQ.
This is the reason they are lighter.

That said, modern zooms produce more than acceptable results.

Keep in mind when using a prime lens that you can zoom ... with your feet
(Safety: Always look first before stepping backwards!)

A 50mm lens on a 35mm sensor/film gives a field of view similar to the human eye.
On a cropped sensor it becomes a good portrait length. I have a 50/1.7 which works well.

For the human eye field of view on a cropped sensor you need around a 35mm lens.
I have a 35/2.4 which is a lot of fun.

[fabian628]

good answers.my idea is

less moving parts/complextity = smaller, size weight. Optics are 'optimised' for a certain focal length. As a consequence you can fit more glass and have a wider aperture in the lens.

the 18-55 is similar size to the 50 1.8 but the 18-55mm at 50mm = f/5.6 is letting in ~ 4x less light

[Arg]

In the old days you definitely wanted fixed-focal-length (so-called 'prime') lenses if you were interested in accurate image reproduction, corner sharpness, wide aperture (shallow focus) effects, or shooting in marginal light conditions with no tripod. Zooms were mediocre (inadequate, even) in all these areas.

Manufacturers have put a lot of effort into zoom lens development since the 80's and narrowed the gap a lot in all the above areas, to the point where the best zooms have no significant deficiencies. Non-specialised professional photographers typically choose an all-zoom kit and get outstanding quality results.

One area prime lenses still rule is if you want quality above all else, and you don't have money. In the $100-$400 range a number of excellent primes can be had, including used (therefore cheaper) specimens from earlier eras that had much the same design and capability as many current model prime lenses. The only optically good zoom I know in that price range is the Canon EF-S 55-250 IS, which is quite cheaply built and only fits a crop sensor camera.

I keep a nifty fifty on my camera on week days for occasional use when commuting and not in 'camera enthusiast mode'. It makes the camera more compact and light and I carry it in a normal bag without worrying about lens damage and expense.

I also have a 100mm macro lens that I consider to be 'special purpose'.

[Ms Monny]

ok, I think I am getting it now. Thanks for all the indepth info on these lenses. I guess if you can always crop a photo down to what you think would look better and if the IQ is better and the lens faster PLUS being cheaper, than I think this may be a good investment for me at the moment. Fabian also showed a good point....a 18-55 is only 5.6f where as the nifty fifty is 1.8f....BIG DIFFERENCE! and being lighter is a bonus!

Might check a few out that are second hand!

[Ms Monny]

Also, Kym, I have heard about this sweet spot on zooms! I guess a fixed lens is ALL sweet?

[arthurking83]

..... I guess a fixed lens is ALL sweet?

Ummm .. not always!

I'm still unconvinced of this 'notion' that primes are generally sharper than zooms .. but then again, and in general, I'm not easily convinced.

One thing's for sure tho.. they do usually have a faster aperture if this is important in your photography.

Other points of noteworthiness with respect to prime lenses, over zooms, is the term Macro. Macro can encompass anywhere between 1:1 magnification, down to 1:3(ie. 33% magnification) and the difference is quite marked when you;ve seen it(if Macro rocks your photographic boat). Where a zoom lens will almost certainly be a 1:3 macro(and hence not really as macro as a proper macro lens!!), there is a 99.9% surety that your prime macro lens is going to magnify all the way to 1:1(very few only go to 1:2 nowadays, and from memory these are very expensive manual focus lenses anyhow).

In general, it's the faster aperture that you really want from that prime lens.

[Ms Monny]

I certainly would love a nice bit of bokeh sometimes!!!

I do get frustrated with the f4 as it doesn't blur enough of the background for my liking, so I guess a prime lens is for me in that situation.

[andylo]

I certainly would love a nice bit of bokeh sometimes!!!

I do get frustrated with the f4 as it doesn't blur enough of the background for my liking, so I guess a prime lens is for me in that situation.

I think you probably knows it already but I might as well mention - you can still create boken even at f4, 5.6 or even f8.

As long as the distance between the lens and the main subject is as close as possible AND THEN the distance between the main subject and the background as FAR as possible, boken still would able to be created, using a telephoto lens help that too.

I got a portrait pic of my missus taken at f/8 at 200mm focal length, boken behind still nice and creamy

[Ms Monny]

Thanks Andy....yes, would you believe I actually only found that one out about a month ago! LOL. Just have to get as close as possible, like you said.

[Kym]

Also, Kym, I have heard about this sweet spot on zooms! I guess a fixed lens is ALL sweet?

NO! Even primes has a sweet spot in terms of Aperture. Typically 2..3 stops closed down or very often around f/8

[Arg]

<snip> I guess a fixed lens is ALL sweet?

Note on nomenclature: a "fixed lens" is normally meant to be one that cannot be removed from the camera body.

"Prime lens" is the normal short form term for a fixed-focal-length lens.

[Bennymiata]

A prime Lens is also know as a Fixed Focal Length Lens - hence "fixed" lens in the context of a DSLR.

Semantics.
It's what keeps these threads going.

[Ms Monny]

Thanks for clearing up the terminology!!

[Brian500au]

Normally the one thing a prime lens will have over a zoom is aperature value - you cannot buy a zoom under 2.8 (and even they are relatively expensive compared to a prime lens). Currently on the market in Canon you can buy a 85 and 50 f1.2, and all the way to 50 f1.4, f1.8, 85 f1.8 etc. At this stage this aperature is unheard of in zooms lens and if it did exist I am sure it would be worth zillions compared to the primes lens in the range.

As for the quality of the zoom - many will testify the Canon 70 - 200 f2.8 MKII zoom is as sharp as any prime lens on the market. Bear in mind the quality of all lens will improve over time - and the quality gap between zoom and prime is narrowing fast.

[ricktas]

They are great for focusing! Everyone seems to be talking about all the benefits of them, except for this one. When a camera uses AF to find focus, it does so at the largest aperture. An f1.8 lens should obtain focus faster than, say an f4 lens, as more light hits the AF system due to the bigger aperture. AF works by seeing the contrast between different elements of the photo, which is why you cannot AF sometimes on a plain blue sky, a dark background, or a subjest with a flat even colour. Using an f1.4 lens means you should be able to get focus, when other smaller aperture lenses will 'hunt' and maybe not lock on focus.

So there are lots of benefits of wide aperture lenses, over those that aren't

[Ms Monny]

Thanks again. The other night I was photographing my family over a birthday cake....well, this is when I thought how much a 50mm f1.4 etc would be PERFECT as I had to really up the ISO just so it wasn't too long an exposure....I could only get my lens down to f4 or f5!

I have noticed the AF part, Rick. If the camera keeps trying to 'find' the focus, I put it into manual and hope my eyes can focus just as good LOL!!

I am really considering this now!