Zooms!......why?

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cherokee1111

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Help me understand here please people as I'm new to DSLR's and having researched to death what I need and should use etc etc heres an overall conclusion that I've arrived at while researching "What new lens to get"....

Apart from the obvious large zooms ( 200+) to enable closer or covert picture captures and taking 'L' lenses out the scenario I just dont see the overall value of zooms like 17-40, 17-55, 15-85 etc etc as its only a few steps to 'zoom' in physically -..theres still an advantage I'll give you that- ....... however.....we all want sharp pictures YES? well when I read up on every lens I was interested in it said to get tack sharp you need to stop down a bit, plus I read the fairly unanimus views across many forums which says "most lenses perform best when stopped down"....which to my mind means I'll never be able to use the 'complete' lens at its best ie sharp pictures throughout the range and I should settle for second best and just shoot in the middle so to speak.......

So whats the point of zooms when a Prime will give more consistent images?

Have I got this all wrong? Have I missed something obvious? Be gentle as I am very new to this and still wanting to learn
 
think you would be better posting this in the correct forum rather than classifieds section???
 
A zoom is a lens used for flexibilty though it is a compromises in quality (in some instances)

A prime lens is going to give better quality though is comprimised by it's lack of flexibility

Hope that makes sense

Most people have short range zoom in their kit for a walkabout so you don't always have to lug equipment round and just use the single lens. A wideangle to short telephoto for instance 28-105 being a good example of a general use.
 
Quite simply framing. For example, I recently shot Salford Quays in Manchester and that's exactly the kind of location a zoom is invaluable because you can't just move your feet, you'd be in the canal!

Zooms are also great when working quickly. At a wedding I need to work quite quickly and zooms are a great way of being able to get the composition right with the minimum of disruption. In a church I often don't have the luxury of moving about so again a zoom does rather a good job of being able to shoot a variety of shots without me moving from my allocated position.

It very much depends what the application is. I'm a huge fan of primes and love shooting with them but zooms are always first on my list.
 
primes are great if you've got all the time in the world but as ali and chivers say zooms are more flexible
 
Good replies :) Flexibility is a good point, its one of the main reasons Im planning on getting a 70-300 VR :)
 
Sometimes you can't physically move.
Think press-work - often Press toggers are coralled into pens they cannot move from. A zoom is invaluable in those situations.
Or take my current line of work - moving off a safe-route could initiate an IED resulting in not only my being a lot shorter all of a sudden, but damaging the cameras too!
 
Thanks for the replies so far...

I really DO GET the scenarios where you can't move etc etc so thats a given..(y)
It's the very small zooms I referred to ie 17-40, 18-55 etc etc that if you use the zoom you'll degrade the picture quality so why not just do a crop and keep the sharp picture as surely a 13mm 'zoom' really isnt that much closer to justify a poorer image?
 
Are they really poor though?

I've no doubt that some modern zooms benefit from the very best computer aided designs, exotic optical glass and optical coating and that some primes were designed long ago and don't.

The shorter zooms incorporating something like x3 zoom probably suffer from fewer compromises and therefore offer the best possible image quality that you can get from a zoom or from a percentage of primes too.
 
cherokee1111 said:
Thanks for the replies so far...

I really DO GET the scenarios where you can't move etc etc so thats a given..(y)
It's the very small zooms I referred to ie 17-40, 18-55 etc etc that if you use the zoom you'll degrade the picture quality so why not just do a crop and keep the sharp picture as surely a 13mm 'zoom' really isnt that much closer to justify a poorer image?
Click to expand...

How will you degrade the picture quality exactly...?

You're suggesting that framing with the lens is somehow going to be worse than cropping a full-frame image?

errr... no....
 
cherokee1111 said:
Thanks for the replies so far...

I really DO GET the scenarios where you can't move etc etc so thats a given..(y)
It's the very small zooms I referred to ie 17-40, 18-55 etc etc that if you use the zoom you'll degrade the picture quality so why not just do a crop and keep the sharp picture as surely a 13mm 'zoom' really isnt that much closer to justify a poorer image?
Click to expand...

They're both pretty decent zoom ranges, especially 18-55. Remember at short focal lengths, a few mm can make a big difference.

You don't change focal length just for 'getting closer' (or further away) either. Your choice of focal length in any given situation will alter the relationship between things in the frame.

Quality difference throughout the range on a decent zoom is negligible. And certainly you'll be better off zooming than cropping.

WRT your first post where you mention stopping down for quality, this relates to the aperture, and is in no way related to the focal length. Most lenses, prime and zoom, perform better stopped down, ie at a smaller aperture, than they do wide open. eg a 50mm 1.8 will be sharper at f/4 than it is at f/1.8. (y)
 
Jayst84 said:
Most lenses, prime and zoom, perform better stopped down, ie at a smaller aperture, than they do wide open. eg a 50mm 1.8 will be sharper at f/4 than it is at f/1.8. (y)
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Which was the point I was about to make then finally came to it. (y) Yes, most zoom lenses will be better stopped down, and most lenses have a sweet spot somewhere between f8 and f11, but the difference between stopped down and wide open [or indeed, stopped way down] will be more and more negligable, the better quality the lens is. Same applies to primes, there will be variation across the aperture range - I have a 28mm Nikkor that is beautiful at f2.8 and stunning at f8...difference is tiny, only just detectable, and its not even top of Nikons expense range. I think you have to remember that it is all relative, and in the case of good quality zooms and prime lenses, the 'differences' are fractions, only really significant to pixel peepers.
 
Why zooms? To some extent at least, because I can't carry as many primes as I might want to use. In just 3 lenses, I have all focal lengths from 12mm to 300 covered and I dread to think how many primes I would need to cover the lengths I actually use on a day out with the kit! Of course, I do also use a few primes - a 90mm Macro for Macro, a 50mm f/1.8 for low light and an 8mm fisheye for fishy shots.

Sometimes, it's quite simply impossible to footzoom - there may well be a 1,000 foot drop between you and the subject and a similar sheer face behind you not to mention Arkady's examples (although I can't see an IED doing much damage to his kit...)
 
I would have thought, forgive me if I'm wrong, that the primary advantage above all else, is that a zoom is one lens - it means you can cover a range of focal lengths without having to carry an array of primes around with you :shrug:

Most photographers I would also assume, would prefer this?
 
cherokee1111 said:
Apart from the obvious large zooms ( 200+) to enable closer or covert picture captures and taking 'L' lenses out the scenario I just dont see the overall value of zooms like 17-40, 17-55, 15-85 etc etc as its only a few steps to 'zoom' in physically -..theres still an advantage I'll give you that- ....... however.....we all want sharp pictures YES? well when I read up on every lens I was interested in it said to get tack sharp you need to stop down a bit, plus I read the fairly unanimus views across many forums which says "most lenses perform best when stopped down"....which to my mind means I'll never be able to use the 'complete' lens at its best ie sharp pictures throughout the range and I should settle for second best and just shoot in the middle so to speak.......

So whats the point of zooms when a Prime will give more consistent images?

Have I got this all wrong? Have I missed something obvious? Be gentle as I am very new to this and still wanting to learn
Click to expand...

cherokee1111 said:
Thanks for the replies so far...

I really DO GET the scenarios where you can't move etc etc so thats a given..(y)
It's the very small zooms I referred to ie 17-40, 18-55 etc etc that if you use the zoom you'll degrade the picture quality so why not just do a crop and keep the sharp picture as surely a 13mm 'zoom' really isnt that much closer to justify a poorer image?
Click to expand...

Can I just clarify what you think 'stopping down' means? From your posts I get the impression that you think stopping down has something to do with the focal length of a lens.

Are you clear about what the focal length and aperture are and why the aperture might be stopped down to get better image quality?
 
Ste Manns said:
I would have thought, forgive me if I'm wrong, that the primary advantage above all else, is that a zoom is one lens - it means you can cover a range of focal lengths without having to carry an array of primes around with you :shrug:

Most photographers I would also assume, would prefer this?
Click to expand...

I agree. Also if you are forever changing primes to get the correct focal length the chances of getting dust on the sensor is far greater.
 
Why not Zooms? With a Sigma 10-20, a 17-55 and a 70-200 f4 IS I have most bases covered for all types of photography and I can carry them around comfortably and quickly in a Crumpler shoulder bag. The fact that zooms make for such portable photography means I'm far more likely to take my camera when out climbing/mountaineering/mountain biking than if I had to lug about a backpack full of primes. I've decided to invest in quality zooms so I don't massively lose out on image quality.
 
By moving your feet you change your perspective (i.e the relationship between objects and how they fit together). By zooming, you change the crop factor (and depth of field).

In an ideal world I would carry 20 prime lenses carried around on a golf buggy, but I can get by with 2 decent zooms.

If you add up the price of these prime lenses - then you can afford L grade glass in the zooms that are pretty good wide open - even if almost every lens made has a sweet spot around f8.
 
"By zooming, you change the crop factor (and depth of field)."

As far as I know the two things that affect DoF are format size and aperture. As far as I know zoom length and crop don't. A crop is just a bit cut out, unless you mean format size and that will affect DoF but zooming doesn't change DoF.
 
woof woof said:
As far as I know the two things that affect DoF are format size and aperture. As far as I know zoom length and crop don't. A crop is just a bit cut out, unless you mean format size and that will affect DoF but zooming doesn't change DoF.
Click to expand...

Both focal length of the lens and the distance between the point of focus and the focal plane (i.e. how far away the subject is) also affect DOF.

So changing the focal length on a zoom lens does affect DoF.
 
The zoom length and magnification within the frame are different things. If the size of the subject in the frame is the same then the zoom length doesn't affect DoF. But I'd still say that zoom length (by itself) doesn't affect DoF.
 
Like someone else mentioned above, focal length isn't only about reaching a far off subject or getting everything close in frame. Lets say you put a 50mm on your camera and walk closer or further away from your subject to take the shot. Your images will be very different from those taken if you zoomed in to 100mm or out to 14mm.

An example of where the images would differ would be compression, where a longer focal length brings the apparent distance of all the elements of the image (foreground and background) closer together. This can be very flattering for portraits. The opposite is true for a short focal length.

To take advantage of these extra creative elements your going to need a short, medium and long lens in your bag, and the time to change them.

Or, just take one zoom!
 
Primes are great but i for one hate lens changing, not only am i lazy but hate to miss a shot and also fear my sensor will be covered in foreign bodies the more i change lenses.

I use a 24-70 f2.8 which i will stop down to f16 for landscapes and f8 for portraits, should i find myself with poor light or wanting a shallow DOF, i can always come back to f2.8 or f4.

Different lenses suit different folks, you make your choice on what you like and how you like to do it.
 
woof woof said:
The zoom length and magnification within the frame are different things. If the size of the subject in the frame is the same then the zoom length doesn't affect DoF. But I'd still say that zoom length (by itself) doesn't affect DoF.
Click to expand...

DOF is a function of focal length, Aperture and subject distance. So 'zoom length' will definitely alter DOF.

A 5D mark II with 70-200 lens at 70mm, f2.8 with a subject at 10ft has a DOF of around a foot. At 200mm the DOF drops to about a 1/10 of that.
 
woof woof said:
The zoom length and magnification within the frame are different things. If the size of the subject in the frame is the same then the zoom length doesn't affect DoF. But I'd still say that zoom length (by itself) doesn't affect DoF.
Click to expand...

Of course it does, that`s why wide angles have a huge depth of field U/wides have so much depth you hardly need to focus.
 
woof woof said:
The zoom length and magnification within the frame are different things. If the size of the subject in the frame is the same then the zoom length doesn't affect DoF. But I'd still say that zoom length (by itself) doesn't affect DoF.
Click to expand...

Just re-read your post. Do you mean that if you zoom in but walk away then the DOF will be the same? If so you are correct, but that doesn't mean the 'zoom length' doesn't alter DOF because by walking away you are changing another variable in the equation.
 
From the first link

The "myth" he is dispelling is that you can zoom in and walk backward to get less DOF. If people think this, then yes I guess it must be a myth because it isn't true. I do however find his images interesting because the backgrounds in the walk backwards/zoom in images do look softer, until compared next too each other.

Please someone correct me if I am wrong, but when you start cropping images to compare DOF at different focal lengths you are effectively simulating shooting the image on a different format, therefore altering the circle of confusion. If you want to demonstrate whether focal length alters DOF then you need to compare images where only the focal length is changed. Once you start moving around or cropping then other elements of the equation are being changed.
 
This online DOF calculator (or any other) works because it uses the equations derived from the physics of light and lenses. You can use it to change the focal length and see the DOF for each value (in the absence of any subjectivity provided by looking at an actual image).

http://www.dofmaster.com/dofjs.html
 
cherokee1111 said:
Apart from the obvious large zooms ( 200+) to enable closer or covert picture captures and taking 'L' lenses out the scenario I just dont see the overall value of zooms like 17-40, 17-55, 15-85 etc etc as its only a few steps to 'zoom' in physically -..theres still an advantage I'll give you that-

A 'zoom' is useful. You can't always move forward or backward to obtain the desired photograph. Some people work in restricted environments and or tight spaces. Also, a zoom will give you the ability to achieve multiple shots with different perspectives compared to a prime, one perspective (fov related). To cover a 24-70 zoom range you would need 3 or 4 primes. This adds to cost.

....... however.....we all want sharp pictures YES? well when I read up on every lens I was interested in it said to get tack sharp you need to stop down a bit, plus I read the fairly unanimus views across many forums which says "most lenses perform best when stopped down"....which to my mind means I'll never be able to use the 'complete' lens at its best ie sharp pictures throughout the range and I should settle for second best and just shoot in the middle so to speak.......

So whats the point of zooms when a Prime will give more consistent images?

A prime lens does not give you consistent images. Often a prime lens is best stopped down too. I have a few primes rated at f/2.8 but perform better a whole stop down at f/4. The same applies to zooms. Lens performance is never (or extremely rare) lateral across a given range. Its one of those you just have to live with.

Have I got this all wrong? Have I missed something obvious? Be gentle as I am very new to this and still wanting to learn

Nothing wrong with learning.
Click to expand...
 
"Please someone correct me"

Personally I try not to think about this stuff for too long because my brain starts to hurt and I feel all inferior :puke::thinking::LOL:
 
I think it's a bit of a myth that zooms provide more flexibility, less weight to carry, cheaper, than trying to cover with primes.

I often go walkabout with my canon 200mm F2.8 , with a 50mm F1.4 and a 1.4TC in my pockets-covering a range of 50mm to 280mm.

To get a similar image quality (although not as good) and range, I would need a canon 70-200mm F2.8.

Doing the sums, my 3 bits of kit together are lighter than the zoom, easier to carry around, and £500 cheaper.

And the 200mm f2.8 is a lot more comfortable over the shoulder than a 70-200 F2.8 being a lot lighter and compact.

I rest my case ;)
 
alastairb said:
you say you have a range of 50-280, that is not true, you have a range of 50,70,200 and 280, this is very different!
Click to expand...

Oh I agree-mine is much more flexible :)

Edit-I have a range of 50, 200 and 280 (the 1.4TC doesn't fit a 50mm F1.4)
 
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