Lens guides

[Agent]

Im looking at getting a DSLR when i have the cash, probably a Canon 350, or simlar.
However, im totaly confused by all the different lenses that are avaliable. Anyone got a good guide on what lens is for what. Which brands to buy / avoid, ect.
Basicly a comprehensive 101 to them

Cheers

[Flibb]

I havent really seen an all in one guide, most people tend to buy a camera and then find a website/forum that deals with their brand.

Generally speaking new lenses from the camera manufacturer will fit their current dslrs. They will be classified by focal length in mm (ie 55mm, 70-300mm zoom etc),folowed by maximum aperature, then a fitting (G is current Nikon), then any other letters tend to be extra fetures like optical coatings , image stabilisation. Heres an example of a Nikon lens

70-200mm f/2.8G G IF-ED AF-S VR zoom

So its a 70-200mm lens, with maximum aperature of 2.8, G lens fitting, IF is internal focussing, ED is the type of glass, AF-S is autofucus servo, and finally VR is vibration reduction.

3rd party companys also make lenses for cameras, best known are Sigma, Tamron and Tokina. Most of their current lenses are available with mounts for all the current DSLRS.
Heres a Sigma lens name
10-20mm f/4-5.6 EX DC HSM
So the first bits we can decode the same as te nikon, EX is basicaly exterior finish, DC is thats its built with digital in mind so the lens can be lighter with smaller glass elements, HSM = HSM (Hyper-Sonic Motor) lens has a servo onboard that is quiet.

Here is a link to the current Sigma lens classification system
http://www.sigma-imaging-uk.com/supp...riviations.htm

Heres a link to the nikonians forum, it has lots of lens test links LINKY . Just about al the current DSLRs are cracking cameras, and for me the choice of one over another was based on a few features i thought would be handy, the kit lens is a good quality (would cost around £200 on its own) and ergonomics when I had a good play with themm. Once I had the camera I used the net to research lenses in my budget. I wanted a longer focal length zoom so just purchased a used 70-300mm sigma, is a bit basic, has slow autofocus but optical quality is good if used correctly (took the squirrel pic with it) and only cost £50. Next lens I found from the nikonians forum, everybody loves it used by all, 50mm f1.8 nikon, again £50.

[noah]

im not doing much this arvo, so i'll have a go at writing something basic. i dont claim to be an expert or know it all but i might be able to offer something to those just starting out.

[BlueMagician]

Check out Luminous Landscape and The Canon Camera Museum.
Plus, have a sniff around Fred Miranda's forum - some interesting, but mostly very talented people there, who will give very good advice if you treat them right. Also, a shedload of decent reviews for most of the respected brands.

A good book to buy if you have the cash is Canon Lens Work III - it explains a fair bit about the technology and history of SLR cameras, plus gives comprehensive examples of shooting styles, lens selection, production and theory.

HTH,
S.

[noah]

lenses: what i know...

right then... lets start with the term people hear most: focal length. "The focal length of a lens is the distance along the optical axis from the lens to the principal focus (or focal point)."

the focal point being the film or the sensor on a digicam, and the lens meaning the first lens in the group of lenses that make up a compound lens that we use.

focal lengths tend to be divided up into 3 rough categories: wide angle, normal and telephoto. wide being usually anything less than about 35mm, normal being 40-60mm and telephoto being anything aver about 70mm.

normal lenses are designed to keep perspective the same in the photo as is seen by the human eye. the perfect length on a 35mm camera is around 45mm but 50mm lenses are normally used because traditionally they were sharper due to the slightly longer focal length.

here you can see that the verticals are straight and the scene looks much as it would through your own eye (without the colour of course )

wide angle lenses tend to change persective, they increase the percieved distance between objects but give a larger field of view. a common wide angle lens is the 28mm, but many use wider lenses for landscapes or tight spaces or even just for effect. extreme wide angles like 15-20mm will heavily distort images, especially straight lines, some such as fish-eye lenses offer up to a 180 degree feild of view.

this image was taken at a focal length of 28mm, it strectches the rider out somewhat.


this image was also taken at 28mm, it givs a nice wide field of view whilst keeping a relatively straight horizintal


here i used a wider lens of 17mm, the field of view is very wide and you begin to see a distortion in the horizon

telephoto lenses give the opposite effect to winde angle lenses in that they have the effect of magnifying objects and bringing them closer. many telephoto lenses are shorter their stated focal length, this is due to them containing telephoto groups which consists of a group of lenses which together act as a single diverging lens causing the lens to focus behind its normal point increasing magnification (i think).

telephoto lenses are used for anything from action sports to portraits. for sports a faster longer lens is needed, usually 200-600mm and for portraits around 100mm is regarded as best. the effect of a telephoto lens on perspective is to compress the image. objects will appear closer together and will often appear slimmer - hence the use for portraits, creating a more flattering image. the depth of feild (area in focus) is also greatly reduced when using a telephoto lens. this may have an attractive effect of drawing the attention towards the focal are of the photo.

a portrait (of the mrs) taken at 100mm, you can see the decreased depth of feild here


a couple of examples of persective compression both taken at 450mm


this is a fair distance out and is taken with a 450mm focal length

there are a few other specialist lenses like tilt and shift lenses that are used for arcitecture and allow perspective correction buy tilting the alignment of the lens, but they are a bit specialised for me to know much about, sorry.

a quick aside to make sure you know what im talking about is the concept of the lens aperture. this is the bit that controls the amount of light that is let through the lens. the shutter then decideds how long the light is let onto the film/sensor for. it looks like this:

nicked from www.howstuffworks.com

the wider the aperture the smaller the f number, eg f3.5 is a big aperture and f22 is a small aperture. therefore the larger the aperture the more light that is let through. the area in focus or depth of feild however becomes smaller with the increasing aperture. the easiest way i find to remember this is that as the f number gets smaler so does the depth of field.

the other factor to consider when buying a lens is the speed of it. when we talk about speed we are referring to the lens' ability to capture an image in low light conditions. if the lens has a faster wider aperture (say f2.8) then we can use a faster shutter speed to freeze the action or prevent camera shake. if a telephoto lens only has an aperture of f5.6 as many cheaper ones do you will find it hard to achieve the required shutter speeds for shooting sports and there will be bags of camera shake visible. the difference between each f stop is double or half the amount of light (depending which way you go), so even a couple of stops can make a large difference to the available shutter speed. unfortunately as a rule fast telephoto lenses are very expensive , fortunately shorter lenses are much cheaper and very good. canon and nikon both make 50mm lenses that are £70-£100 and are very very fast having a max aperture of f1.8 in both cases.

this was taken with a wide aperture of f3.5 you can see the smaller depth of field


here you can see the effects of 450mm telephoto and f5.6 combined to give a very small depth of feild

lens also come in different grades, posh ones and cheap ones. each brand has a different notation for their nicer lenses. nikon use ED, canon use L and sigma use EX. all these leses are made from higher spec glass and give much sharper imges than the cheaper lenses aspcially the telephoto and macro ranges where sharpness really counts. the thing to watch for is nikon slap the ED tag on some cheaper lenses that only use 1 or 2 bits of ED glass, but i'm sure you will soon tell with the difference in price which ones are pro quality and which ones arent. sigma also use the notation APO which is used on all lenses that have a special coating to minimise chromatic abberation (purple or blue fringing) on high contrast areas. HSM and USM are high speed quiet focusing systems used on some lenses. Vibration reduction (VR) or image stabilisation (IS) are used to compensate for lens shake.

with the new digi slrs people are making lenses that cater specifically for them. this is usefull as film is essentially 2D but a digital sensor is 3D. it is like a series of pots designed to collect light and turn it into a signal. because light comes from different angles it doesnt fill every pot equally, as far as i know these digital lenses attempt to correct this. (this is how it was explained to me, its may not be the exact case)

will probably add more later as i think about it hope this helps, let me know what to put in to imrove it. i glanced over some of the acronyms and will add more about them and talk about internal and external focusing. i would talk about the difference in focal lengths using a alens on an aps-c sensor and on film but shiato already covered that very well in another post.

ALL FOCAL LENGTHS ARE QUOTED IN 35MM EQUIV TERMS

ALL PICTURES ARE FROM MY LIBRARY ARE MY COPYRIGHT

[shiato storm]

edited... made an error, will correct it in a bit, though maybe we could get a mod to make noah's post a sticky...a sort of 'lenses the basics'

[Funkstar]

not read it yet, but that looks like a lot of help here noah

[BUFF]

ALL FOCAL LENGTHS ARE QUOTED IN 35MM EQUIV TERMS

This is very important as most DSLRs have a crop of 1.5-1.6 i.e. a lens with a focal length of 50mm on a 35mm film camera will have an efffective focal length of 75mm on a DSLR (50x1.5 assuming 1.5 crop)

[noah]

yeah i thought about covering that, but shiato did a great job of it here ...

http://forums.hexus.net/showthread.php?t=59786

iirc nikon has 1.5x and canon 1.6x and olympus 2x

[BlueMagician]

..iirc nikon has 1.5x and canon 1.6x and olympus 2x...

Indeedy, but Canon bodies vary.
The 1ds, 1dIIs and the new 5D are full frame, the 1d and 1dII are x1.3, and the 300D/350D/20D/20Da are all x1.6

S.

[menthel]

And for when you work out what you want, look here for some excellent reviews of various lenses:

http://www.fredmiranda.com/reviews/index.php

[noah]

Indeedy, but Canon bodies vary.
The 1ds, 1dIIs and the new 5D are full frame, the 1d and 1dII are x1.3, and the 300D/350D/20D/20Da are all x1.6

S.

a very good point, i wasnt thinking above my price range!

im not sure why canon keep changing their sensor sizes tbh, seems a little odd, im sure they have a plan there somewhere...

[BlueMagician]

...im not sure why canon keep changing their sensor sizes tbh, seems a little odd, im sure they have a plan there somewhere...

I'm pretty sure it's just a cost of production issue on the sensors. Full frame is there for people who've got £3500+ to blow on a body that'll be superceded in 15months, where as the crops are there for the prosumer, keeping costs in the un-scary region.. Nice guide, btw..

S.

[fuddam]

just remember, the quality of the GLASS you buy is all important. You will prob change bodies / upgrade sometime down the line, but you want to buy good lenses to last a lifetime.

You should run around some dedicated photo forums, but essentially the following holds true:

the larger the maximum aperture, the more costly it will tend to be but also the better quality it will be. And if you have zoom then a constant aperture (one that doesn't change) will be better quality than one that does change

eg 80-200mm 2.8 is better than 80-200mm 4 - 5.6

I'd say generally, if you can afford it, stick with top brand lenses, and the rest will fall into place. Some 3rd party manufacturers produce good lenses, but none seem to do it consistently. Eg Tamron has a 90mm portrait lens that drew a LOT of praise for years IIRC, but some of their other lenses are average. I like some of the Tokina lenses, but that's just my experience.

If I was buying lenses to start out, I'd go with the following (assuming either Canon or Nikon DSLR bottom end):

1) kit lens approx 18-70mm
2 ) zoom 80-200

if you have the cash, the nikon 12-24mm is sweeeet, and covers the wide angles, and the new 70-200mm VR is even better but in major demand and not cheap

try to avoid those 28-200mm lenses, unless you sticking to solely amateur ambitions, IMHO. There's always a compromise to get such range.

[BlueMagician]

...just remember, the quality of the GLASS you buy is all important. You will prob change bodies / upgrade sometime down the line, but you want to buy good lenses to last a lifetime...

I couldn't agree more with this. Just be careful when visiting forums like FM. You'll get sucked into an alternate reality - into a world where the smell of melting credit cards is around every corner... <hangs his head in shame>

S.

[BUFF]

(assuming either Canon or Nikon DSLR bottom end):

Don't forget the Konica-Minolta Dynax 5D as it's a very strong contender against the 350D or D50.