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Zoom and millimeters
As a compact camera /img/avatar4.jpg (currently a Sony DSC-H1) I'm looking at buying a DSLR (probably a Sony a350) but I still can't figure out how to compare my current 12x optical zoom with a lens in mm..

Someone told me that a 18-200mm is a 11x zoom because of 200 divided by 18 is about 11 times, but does that mean that a 50-200mm is only a four time zoom ? .

It would mean the 18-200mm is an equivalent of my 12x optical zoom... but I suppose that is also to easy ?

Comments (9)

The zoom range is figured by divided the longest focal length (in the case of your current camera, it's 432mm) by the shortest focal length (36mm). So, your camera is a 12x zoom. Normally, the higher the zoom range, the lesser the optical quality of the lens..

A more important issue rather than the zoom range is the focal length. As an example, an 18-200 lens will give you a wider angle of view than your current camera. You also have to deal with the crop factor, which is typically 1.5-1.6 times the focal length, when dealing with a DSLR. With most Nikon DSLRs, the crop factor is 1.5. This means the 18-200 lens is the equivalent of a 27-300 in 35mm camera terms. Just like your current camera is a 36-432 lens in 35mm..

So, depending on what types of photos you like to take, a wider lens or a longer lens may be of more use to you. Or, you can buy more than one lens to cover your needs..

Regards,Jeffhttp://www.jhudson.zenfolio.com..

Comment #1

Pnicolay wrote:.

As a compact camera owner (currently a Sony DSC-H1) I'm looking atbuying a DSLR (probably a Sony a350) but I still can't figure out howto compare my current 12x optical zoom with a lens in mm..

That camera was a 36mm to 432mm equivalent range. For a Sony DSLR that would be a 24mm to 288mm lens (doesn't exist)..

Someone told me that a 18-200mm is a 11x zoom because of 200 dividedby 18 is about 11 times, but does that mean that a 50-200mm is only afour time zoom ? .

Yep. And it means a 50mm prime is a 1x  Less zoom means better optical quality all else being equal. Also Superzoom lenses are only their advertised focal length at infinity and are much shorter nearer their minimum focusing distance. The Tamron 18-250 is reported to be effectively 125mm at the long end when at minimum focusing distance..

It would mean the 18-200mm is an equivalent of my 12x optical zoom...but I suppose that is also to easy ? .

Well, they are both about 12x, but the 18-200 is wider. The Bigma (Sigma 50-500) is a 10x zoom, but twice as long as anything you are looking at. So basically, you should look at what ranges you shoot now and decide what focal lengths you need, because the actual zoom range of the lens doesn't determine anything. You could get a 400mm prime (600mm 35mm equivalent) that doesn't zoom at all..

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Comment #2

Pnicolay wrote:.

As a compact camera owner (currently a Sony DSC-H1) I'm looking atbuying a DSLR (probably a Sony a350) but I still can't figure out howto compare my current 12x optical zoom with a lens in mm..

Someone told me that a 18-200mm is a 11x zoom because of 200 dividedby 18 is about 11 times, but does that mean that a 50-200mm is only afour time zoom ? .

Yes. 18 x 11 is 198. so the 18-200 is essentially an 11x zoom. 50 x 4 is 200, so it's 4x..

It would mean the 18-200mm is an equivalent of my 12x optical zoom...but I suppose that is also to easy ? .

Zoom range isn't focal range. A 25-250mm lens would be 10x, as is the Bigma 50-500mm. In terms of traditional 35mm equivalence, 50mm would be the point of essentially no magnification. Shorter than 50mm is going into wide angle territory, longer than 50mm is telephoto. A 300mm lens would give the magnification of a 6x pair of binoculars..

Digicams are often referred to in terms of 35mm equivalence because due to the multiple different sensor sizes, using the actual focal lengths would tell you the zoom range but might be very hard to use to compare the effective wide angle or telephoto results..

There is a certain amount of "rounding" allowed in describing lenses although it's typically at the long end. That 18-200 might actually be 195mm or 205mm instead of 200. However, at the wide end, focal length differences are much more apparent and the range from 10mm to 12mm to 14mm would be very apparent in use. The focal length is calculated at infinity and there is potentially some difference when used at shorter ranges, the actual differences depends on the design of the lens, some but not all are markedly shorter...

Comment #3

Pnicolay wrote:.

I still can't figure out howto compare my current 12x optical zoom with a lens in mm..

The number 8x, 10x, 12x, is a meaningless marketing term that only tells you the range from the shortest (widest) position of the lens, to the longest (telephoto) end of the lens. For instance, 18-180, 28-280, 50-500 are all 10x lenses, but they have very different optical characteristics..

Your H1 has an equivalent (in 35mm camera terms) of 36-432mm...assuming that "normal" (human eyes) are 50mm, your camera is long on the telephoto end, but not very wide on the wide end (which may be fine for you)..

Knowing the range in mm of your current camera you can now make a PROPER comparison, and forget all of the "X" stuff..

Actually, as you get better you may want LESS "X" in your lens...the longer the range from wide to tele the lens is, the more potential for distortion like curved images, colour distortions, etc. Many photographers will use lenses that CAN'T zoom, they only have one focal length (like 50mm, 105mm, etc.). They use those when they want the best optical quality since the optics are designed for one focal length, rather than be adjusted...

Comment #4

Mike_PEAT wrote:.

Your H1 has an equivalent (in 35mm camera terms) of36-432mm...assuming that "normal" (human eyes) are 50mm, your camerais long on the telephoto end, but not very wide on the wide end(which may be fine for you)..

Knowing the range in mm of your current camera you can now make aPROPER comparison, and forget all of the "X" stuff..

While I understand that buying lenses is much more than comparing zoom factors, for a beginner in DSLR it is one of the only things he can compare. Knowing how I felt when I started using compact camera's (with only 3x zoom) and when I moved to the DSC-H1... it would definitely be a disappointment if I would go back again with for example an Sony a350 with 18-250 and realizing that it doesn't zoom "as well" (even if it is a marketing hype, and there are much more factors in quality DSLR photograping)..

While multiple lenses and prime lenses are an asset, I'm just wondering what an ideal starter set (both in price, and ease of use, ie. nog constantly changing lensens) in DSLR would be for me...

Comment #5

I used to think this way too but soon realise dthat the poor AF of my superzoom compact meant I rarely managed any great images at long focal lengths..

In your case, yes the 18-250mm lenses are ideal as a starting point but the IQ improvement will not be as good as say a 16-5 and a 50-200 combined..

Pnicolay wrote:.

Mike_PEAT wrote:.

Your H1 has an equivalent (in 35mm camera terms) of36-432mm...assuming that "normal" (human eyes) are 50mm, your camerais long on the telephoto end, but not very wide on the wide end(which may be fine for you)..

Knowing the range in mm of your current camera you can now make aPROPER comparison, and forget all of the "X" stuff..

While I understand that buying lenses is much more than comparingzoom factors, for a beginner in DSLR it is one of the only things hecan compare. Knowing how I felt when I started using compactcamera's (with only 3x zoom) and when I moved to the DSC-H1... itwould definitely be a disappointment if I would go back again withfor example an Sony a350 with 18-250 and realizing that it doesn'tzoom "as well" (even if it is a marketing hype, and there are muchmore factors in quality DSLR photograping)..

While multiple lenses and prime lenses are an asset, I'm justwondering what an ideal starter set (both in price, and ease of use,ie. nog constantly changing lensens) in DSLR would be for me..

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Pentax Lens examples at http://www.pbase.com/alfisti/images_by_lens.

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Comment #6

Pnicolay wrote:.

- - - Snip! Snip! - - -.

While multiple lenses and prime lenses are an asset, I'm justwondering what an ideal starter set (both in price, and ease of use,ie. nog constantly changing lensens) in DSLR would be for me..

Hi,.

Can't say this politely but here goes: the main reason for most people to buy a dSLR *is to change lenses* and get exactly what they need for the shot. One lens suits all is lies (below NASA budgets, of course)..

As for a a good kit, either get something that goes from 28mm (in 35 mm film terms) and would be good for interior shots to about 85/90 for portraits (That's what most need most of the time). Or get something that's wide to standard and standard to tele but beyond 300mm you'll not be able to hold it still most of the time and 200mm for hand held is much easier if less impressive in the adverts. If you need 200mm + then look for a specialised lens and abandon the budget..

BTW, the focal length doesn't change as you focus nearer but the FoV does. Many people see this as a good thing as you get less un-necessary background in the shot. Look at ebay pictures to see what I mean....

Regards, David..

Comment #7

David Hughes wrote:.

BTW, the focal length doesn't change as you focus nearer but the FoVdoes..

Not so sure about this. In the case of a lens which is focussed by moving the entire lens back and forth, the focal length is of course unchanged. But many lenses focus by moving some of the elements relative to each other during focussing. So it is entirely feasible that the focal length may vary as focus is adjusted.Regards,Peter..

Comment #8

Take your shots you took with Sony H1 and group them by focal length (36-80 mm; 80-200 mm; 200-432 mm) and see the weights. I would bet that 90% are in the first group, 7-8% in the second and the rest in the third group. If this normal distribution is true fro you you would be very well served by the all around lens (like 16-105 mm from Sony, 16-85 mm from Nikon or 17-85 mm from Canon)..

Trying to get the same range in the dSLR camera would mean a marginal improvement over your superzoom. I would keep that Sony H1 for the 2-3% that goes beyond what an all around lens will give you..

As you can see that these lenses are quite expensive and they have "just" 5-6x zoom.VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/http://picasaweb.google.com/teodor.nitica/..

Comment #9

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