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Zoom and Optics understanding?!!!
On dp review, their learning center describes a 28-280mm point and shoot to equall a 10x optical zoom. Now I understand how they came up with that, but for dslr lenses, it just dosent make sense!.

For instance, Expensive Telephoto lenses with 100-400mm zoom for, (one of canons or nikons I think) does that mean the camera only has a 4x optical zoom? Or is the entire measurement process for optical zoom DSLRS lenses diffrent? PLEASE HELP!!!!!! EXPLAIN!..

Comments (17)

The 10x refers to the magnifacation ratio from 28-280 280/28 = 10 On a 1.6 crop camera the 28mm = 45mm FOV and the 280mm = 450mm FOV...450/45 Still a 10x Magnifaction Ratio/.

At 200mm on a FF 35mm is only 4x a NORMAL PRIME LENS of 50mm...on a 1.6x Crop DSLR the FOV = 320mm......Only 6x from a 50mm on a FF 35mm.

Now on a 1.6x CROP...a 30mm is a normal lens, so....a 200mm would give a 6.6x from a normal lens.....Like looking through a pair 6.6x Binoculars from a 1.6 crop point of view..

Mike22490 wrote:.

On dp review, their learning center describes a 28-280mm point andshoot to equall a 10x optical zoom. Now I understand how they came upwith that, but for dslr lenses, it just dosent make sense!.

For instance, Expensive Telephoto lenses with 100-400mm zoom for,(one of canons or nikons I think) does that mean the camera only hasa 4x optical zoom? Or is the entire measurement process for opticalzoom DSLRS lenses diffrent? PLEASE HELP!!!!!! EXPLAIN!.

Peter .

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Enjoy your photography images, even if your wife doesn't ! ;-(http://laurence-photography.com/http://www.pbase.com/peterarbib/Cameras in profile...

Comment #1

Mike,.

It means that the LENS has a 4X zoom ratio. Zoom ratio is always a lens measurement. The camera, since it can change lenses, can have whatever zoom ration the lens used has..

In long telephotos, the cost is not a function of the zoom ratio, but of the cost of the more expensive materials often used, the lower production quantity, etc..

The shorter zoom ration means it is more practical to carry and use compared to other choices..

John.

Mike22490 wrote:.

For instance, Expensive Telephoto lenses with 100-400mm zoom for,(one of canons or nikons I think) does that mean the camera only hasa 4x optical zoom? Or is the entire measurement process for opticalzoom DSLRS lenses diffrent? PLEASE HELP!!!!!! EXPLAIN!.

Van..

Comment #2

Extended range zooms (like the 10x zoom range you mention) are convenient as they cover the whole range from wide angle to powerful telephoto so will do everything you want. Lots of compact and bridge cameras have these. However this wide zoom range comes at a price: specifically a loss in image quality. It is very difficult to make a zoom lens that performs very well across the whole range: you will get distortions, vignetting, low resolution etc. etc. creeping in.



Lenses for DSLRs are more likely to have a narrower zoom range for two reasons. Firstly, because it will give higher image quality; on average a DSLR user is more likely to be concerned about image quality and will pay extra for a 100-400 lens (for example) or a 50-200 that 'only' has a 4x zoom range if the image quality is good. Secondly, DSLRs are inherently bigger and bulkier, so wide-range zooms can be big and cumbersome. They do exist for DLSRs however; Tamron make a well-regarded 18-250 (13 x zoom) for example. It's just that the fussier you are about image quality, the less likely you are to want one of these. This is why lenses such as the Canon 17-40 (with a mere 2.5x zoom range) are bought by professional or discerning amateur photographers for whom image quality is more important than weight or convenience..

Best wishesMike..

Comment #3

Cheers from John from Adelaide, South AustraliaJohn Harvey Photography http://johnharvey.com.auCanon 40D, Canon 20D & Fuji F10..

Comment #4

Hi,.

Trouble is, you are only looking at the zoom range and there are other things a little more important..

A x10 zoom might go from 28mm (in 35 film terms) but will/may be only f/35 at best and at the telephoto end may well be something like f/8. A small aperture like that restricts the range of shutter speeds you can use, unless the ISO rating is boosted which brings in noise problems and so on..

So dSLR's give you lenses to die for (that's a quote from the BJP's review of the Olympus E-3) that cost an arm and a leg but are superb like the (medium price) 70 to 200 mm (in 35mm film terms) that are f/2 all the way through the range..

Now look at what "medium price" means at this end of the range... And try the dearer ones to see what you get for your money..

The point about a dSLR, or a film one, is that you can put together a set of bodies and lenses to suit whatever you to do but a mass market one tends to look good in the advert and be restricted in reality. (x10 sounds great doesn't it? No point in looking any further, perhaps?) Try taking wildlife in the woods, in winter and you'll see what I mean..

I blame the marketing people who want a dramatic headline to grab your attention..

Regards, David..

Comment #5

Thanks for all the help guys!!! So zooms ratios are the same for all lenses, it's just the build quality of the dslr lens that adds the huge price fix!~~~~ thanks again!!!!!! ..

Comment #6

Udaman wrote:.

The 10x refers to the magnifacation ratio from 28-280 280/28 = 10 On a 1.6 crop camera the 28mm = 45mm FOV and the 280mm = 450mmFOV...450/45 Still a 10x Magnifaction Ratio/.

It doesn't refer to the magnification ratio. Magnification is the ratio between the image height to the object height, and therefore is an indication of the maximum image size you can achieve relative to the actual object size. A 1:1 magnification means an object the size of the camera's sensor will fill the sensor 100%, thus 1:1..

You are describing "zoom ratio" which is not related to magnification. I suspect you knew this, but jumbled your terminology..

At 200mm on a FF 35mm is only 4x a NORMAL PRIME LENS of 50mm...on a 1.6x Crop DSLR the FOV = 320mm......Only 6x from a 50mm on a FF35mm.

Now on a 1.6x CROP...a 30mm is a normal lens, so....a 200mm wouldgive a 6.6x from a normal lens.....Like looking through a pair 6.6xBinoculars from a 1.6 crop point of view..

Mike22490 wrote:.

On dp review, their learning center describes a 28-280mm point andshoot to equall a 10x optical zoom. Now I understand how they came upwith that, but for dslr lenses, it just dosent make sense!.

For instance, Expensive Telephoto lenses with 100-400mm zoom for,(one of canons or nikons I think) does that mean the camera only hasa 4x optical zoom? Or is the entire measurement process for opticalzoom DSLRS lenses diffrent? PLEASE HELP!!!!!! EXPLAIN!.

Peter .

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Enjoy your photography images, even if your wife doesn't ! ;-(http://laurence-photography.com/http://www.pbase.com/peterarbib/Cameras in profile..

Tim'Be the change you wish to see in the world.' -Mahatma Gandhihttp://www.flickr.com/photos/timskis6/..

Comment #7

Peter .

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Enjoy your photography images, even if your wife doesn't ! ;-(http://laurence-photography.com/http://www.pbase.com/peterarbib/Cameras in profile...

Comment #8

Mike22490 wrote:Thanks for all the help guys!!! So zooms ratios are the same for alllenses, it's just the build quality of the dslr lens that adds thehuge price fix!~~~~ thanks again!!!!!! .

Not just the build quality but the aperture range as well....

A slow variable aperture DSLR zoom lens that goes from f3.5 at the wide end to f5.6 at the tele end will be a lot less expensive than a fast constant f2.8 aperture zoom of the same range which will be very expensive....

Other features that make DSLR lenses more expensive is if the lens has a focus motor (AF-S for Nikon lenses) that let them focus very quickly and quitely....

Hope this helps....

Bob.

Photography is more about depth of feeling than depth of fieldhttp://www.pbase.com/mofongo..

Comment #9

David Hughes wrote:.

Hi,.

Trouble is, you are only looking at the zoom range and there areother things a little more important..

A x10 zoom might go from 28mm (in 35 film terms) but will/may be onlyf/35 at best and at the telephoto end may well be something likef/8. A small aperture like that restricts the range of shutter speedsyou can use, unless the ISO rating is boosted which brings in noiseproblems and so on..

So dSLR's give you lenses to die for (that's a quote from the BJP'sreview of the Olympus E-3) that cost an arm and a leg but are superblike the (medium price) 70 to 200 mm (in 35mm film terms) that aref/2 all the way through the range..

Hi David. Yes, exposure is important, but even at f/2 for the lens you mention, DOF is the same as using f/2.8 for a 70-200 lens on a FF camera. I'm not trying to bash as I'm sure the Oly offerings are perfect for people who want what they bring to the table. It's just that there's more to equivalence with f/ratios and apertures than there may seem to be at first glance..

Now look at what "medium price" means at this end of the range... Andtry the dearer ones to see what you get for your money..

The point about a dSLR, or a film one, is that you can put together aset of bodies and lenses to suit whatever you to do but a mass marketone tends to look good in the advert and be restricted in reality.(x10 sounds great doesn't it? No point in looking any further,perhaps?) Try taking wildlife in the woods, in winter and you'll seewhat I mean..

I blame the marketing people who want a dramatic headline to grabyour attention..

The average consumer is as much a part of this as anything else. I think it's as much marketers responding to what they think consumers want as influencing consumers with the marketing..

All that said, like many more serious photographers, I'd much prefer camera makers to seek to improve IQ instead of increasing all the numbers in the specs, often at the expense of IQ..

Regards, David.

Cheers from John from Adelaide, South AustraliaJohn Harvey Photography http://johnharvey.com.auCanon 40D, Canon 20D & Fuji F10..

Comment #10

John down under wrote:.

- - Snip! - -.

Hi David. Yes, exposure is important, but even at f/2 for the lensyou mention, DOF is the same as using f/2.8 for a 70-200 lens on a FFcamera. I'm not trying to bash as I'm sure the Oly offerings areperfect for people who want what they bring to the table. It's justthat there's more to equivalence with f/ratios and apertures thanthere may seem to be at first glance..

Hi,.

Yup but the point I was making is/was that I need f/2 to give some choice of shutter speed and low ISO for silky smooth prints. DoF doesn't come into it for me as fleeting wildlife is never there for long enough to start thinking of such luxuries as DoF and even time to think is a luxury at times..

Also a lot of x 12' s at the far end with f/8 (perhaps) are going to select a slow shutter speed that just won't be possible without camera shake and IS ain't that marvelous. Best to forget you have IS in my opinion and stick to old fashioned techniques (like jamming the thing against a tree)..

Regards, David..

Comment #11

Ok last question I promise, I under stand zoom lenses now, but what about fixed zoom lenses!(ones you cant zoom in and out of).

What would be the optical zoom of say, a 200mm fixed lens? Or does it take in account for other factors...

Comment #12

Hi,.

I am being very polite when I say that you can't zoom it as it is fixed. Simple as that: called a "prime" by the way..

Regards, David..

Comment #13

Mike22490 wrote:.

Thanks for all the help guys!!! So zooms ratios are the same for alllenses, it's just the build quality of the dslr lens that adds thehuge price fix!~~~~ thanks again!!!!!! .

One point that has not been mentioned is that compact, fixed-lens cameras typically have short-back-focus lenses, which deliver better IQ at lower cost. So, it may or may not be a build quailty issue..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #14

David was kind..

Mike22490 wrote:.

Ok last question I promise, I under stand zoom lenses now, but whatabout fixed zoom lenses!(ones you cant zoom in and out of).

You don't (yet) have a clue! The expression "fixed zoom lenses" is an oxymoron..

What would be the optical zoom of say, a 200mm fixed lens?.

It is exactly one. Since it doesn't zoom, the numerator and denominator are equal, so when you divide one by the other, you get ONE....

Or does it take in account for other factors..

Probably...don't have a clue what you were fishing for?.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #15

The maximum focal length 200 mm. The minimum focal length 200 mm. So the zoom ratio is 200/200 = 1x..

Usually prime lens are faster and better than any zoom lens with the price of lack of flexibility..

Mike22490 wrote:.

Ok last question I promise, I under stand zoom lenses now, but whatabout fixed zoom lenses!(ones you cant zoom in and out of).

What would be the optical zoom of say, a 200mm fixed lens? Or does ittake in account for other factors..

VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/http://picasaweb.google.com/teodor.nitica/..

Comment #16

It sounds like you're confusing zoom ratio with focal length. Focal length is related to how far away the object appears to be. The higher the focal length, the closer the object appears. A higher focal length lets you "zoom in" on distant things. It does this by narrowing your field of view..

To get an idea of what is meant by field of view, try the following excercise:.

Without moving your head or your eyes, notice how far to the side you can see. I'm estimating here, but you can probably see about 160 degrees from your left sife to your right side. Now: put an empty toilet paper tube up to your eye. Now all you can see is a small slice of the world, maybe only 5 degrees. What the lens in the camera does is take that small 5 degrees and fill the whole sensor with it! That's why something seems so much closer. This is the effect of focal length..

The zoom ratio is just describing the range of the lens, in Strictly Relative Terms! you could have a 10X optical zoom from 5-50mm, or a 10X optical zoom from 55-550mm. In this case, though the zoom factor is the same, the range of magnifications you will see through the lens are very different. In fact, in this made-up example, they do not even overlap. It would be literally impossible to get the same image through them - they are simply made for different things...

Comment #17

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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