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Old Mar 3, 2008, 4:16 AM   #1
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Background; I am looking for camera to take when I'll go on holiday to Africa in July, and as I am hoping to take lots of nice closeups of lions eating zebras etc etc I know i need a decent zoomrange. I haven't decided yet on what to go for and I am waiting to see what comes out in next few months to see if there will be anything superior to something like currentpanasonic/fuji superzooms.



Anyway, I am struggling to work out what kind of zoomrange i'll need to look at, 10x sounds reasonable till you realise that magnification depends on the starting value; i.e a 10 xcould just go to280 mm if the starting length is 28 mm, which isn't really the same as a 10x magnification as i would get with binoculars which have a 10x magnification.



I also now gather that the size of the sensor has some bearing on the real magnification and that a 300 mm focal length on a digital camera doesn't equate with a 300 mm length on the old fashioned film slr. And is there difference between a 300 mm on a dslr or adigital P&S??



So, who understands all this and clarify how all this works, and can suggest what kind of zoomrange i'll need to look at in either dslr or superzoom for the purpose required?



thanks
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Old Mar 3, 2008, 5:52 AM   #2
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The actual focal length of a lens remains the same regardless of the sensor size but the field of view and effective magnification differs significantly.

Most DSLRs have an APS-C size sensor which gives a narrower field of view than the same lens on 35mm. Generally speaking this gives a field of view equivalent to 1.5 or 1.6 times that given by the same focal length on a 35mm film camera. The Olympus cameras give a narrower field of view again.

So on a 35 mm film camera 50mm is considered a normal field of view and 500mm would give 10 times magnification. For a DSLR this is more like 35mm and 350mm for the same field of view.

With compacts it's more difficult as there are a range of sensor sizes but helpfully most cameras quote a 35mm equivalent focal length. This tells you what focal length lens you would need to get the same field of view on a 35mm camera. So when the Panasonic quotes 28-280 there's no way this is the true focal length of the lens but it's the 35mm equivalent focal length. I doubt very much that you'll find a compact with the sort of magnification you're looking for.

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Old Mar 3, 2008, 9:35 AM   #3
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First, most introductions of new digital cameras have already happened at PMA last month, so there probably won't be any significant new product introductions until just before the holiday shopping season.

Second, I agree with Nagasaki. The 35mm equivalent focal length is the specification you should concern yourself with. If you do that, then the size of the image sensor is already taken into account.
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Old Mar 3, 2008, 10:35 AM   #4
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wittetulp wrote:
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Background; I am looking for camera to take when I'll go on holiday to Africa in July, and as I am hoping to take lots of nice closeups of lions eating zebras etc etc I know i need a decent zoomrange. I haven't decided yet on what to go for and I am waiting to see what comes out in next few months to see if there will be anything superior to something like currentpanasonic/fuji superzooms.
...
Whatever camera you decide on, don't wait to get the camera. It takes some time to get used to a camera - you really don't want to spend your vacation reading the manual or trying to remember how to change the ISO while a rhino is charging your Jeep.

Take some time to work with your new camera. In particular, take it out to the country side and do some landscape work - something you are likely to want to do in Africa. Also take it to a local zoo. That will give you an idea of how close you have to be to various animals to get a decent photo. (I believe you will find that if you want get a good close up of a lion eating something, it will have to be close enough to be thinking of eating you.)
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Old Mar 3, 2008, 11:38 AM   #5
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my understanding now is that in any digital camera, whther compact or dslr, the quoted focal length takes account of the sensorsize and adjusts for it, and that 350 mm would give a 10x magnification, which would be equivalent to 500mm in the old film slr. Is that correct

i can see the argument for practising with my chosen camera, and the sooner the better, however, i somehow cannot cope with the idea odf splashing out on either something like the FZ18, or even a "starter slr", and then finding out that the new sony dsc h50 or one of the new fuji's is going to be superior to whatever I bought. If I buy in May or June, I'll still have 1-2 months to practice. I do have many of the skills already, i used to use a film slr until I got my canon A45 as a second camera which produced such a beautiful results that my old slr han't been touched for years.
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Old Mar 3, 2008, 11:56 AM   #6
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wittetulp wrote:
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my understanding now is that in any digital camera, whther compact or dslr, the quoted focal length takes account of the sensorsize and adjusts for it, and that 350 mm would give a 10x magnification, which would be equivalent to 500mm in the old film slr. Is that correct
No. The 35mm equivalent focal lengthis the 35mm equivalent focal length. The magnification is a real number that varies from camera to camera and lens to lens.

The problem is that the focal length of a lens gives different angles of view, and different magnifications,depending on the size of the image sensor (film or digital.) When manufacturers quote a 35mm equivalent focal length, it is an attempt to provide pothential buyers with a common framework from which to compare one camera with another. When you have a 35mm equivalent focal length, you don't need to do any additional math to make the comparison. A 350mm lens is not equivalent to a 500mm lens, it's equivalent to another 350mm lens.
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Old Mar 3, 2008, 12:21 PM   #7
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The terminology is confusing at times and often depends on whether you are talking about a compact or a DSLR.

With compacts the actual focal length is not given but a 35mm equivalent focal length is given. In this case a 350 mm equivalent focal length would give roughly 7 times magnification the same as a 350mm lens on a 35mm camera.

With DSLR lenses the actual focal length is given. So a 350mm lens on a DSLR is still a 350mm lens however where this lens gives a 7 times magnification on a 35mm or full frame camera it will give approximatly 10 times magnication on a APS-C sensor DSLR or roughly equivalent to the field of view of a 500mm lens on a 35mm film or full frame digital SLR. On an Olympus DSLR the same lens would give the field of view of a 700mm lens on 35mm film.

When talking about magification you also need to be clear what you are talking about. When I talk about 10 times magification I mean the field of view is 1/10 of the field of view of the human eye. A lens doesn't magnify any more when put on smaller sensor cameras the camera crops out a portion of the available image created by the lens.

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Old Mar 3, 2008, 12:38 PM   #8
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try again then; i understood it with the old filmcamera's; the slr with the 50 mm lens gave the kind of "normal" image whilst the compact cameras used to have a 35 mm lens (??) giving the"wider view"





Quote:
So on a 35 mm film camera 50mm is considered a normal field of view and 500mm would give 10 times magnification. For a DSLR this is more like 35mm and 350mm for the same field of view.
this seems to suggest it is different for digital camera's and this confuses me.

to ask it as simple as possible; taking the same picture from the same distance with a 100mm lens with either film slr, digital slror "superzoom", will all three pictures show the same magnification, and hence show all objects at the same size??


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Old Mar 3, 2008, 1:03 PM   #9
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wittetulp wrote:
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this seems to suggest it is different for digital camera's and this confuses me.

to ask it as simple as possible; taking the same picture from the same distance with a 100mm lens with either film slr, digital slror "superzoom", will all three pictures show the same magnification, and hence show all objects at the same size??

Simple answer no.

On a DSLR with an APS-C sensor you'd get a field of view about the same as you would with a 150mm on 35mm film, with an Olympus 4/3 DSLR you'd get the same field of view as a 200mm lens would give on 35mm film.

It just doesn't really apply when you come to superzoom compacts.

Taking one at random the Canon Powershot S3 has a lens with a zoom lens of 6 to 72mm a 12 times zoom. This gives the same field of view as a 36-432mm zoom lens on a 35mm camera. so if a 100mm lens was available with this sensor it would give the same field of view as a 600mm lens would on a 35mm camera. Just to make it more confusing the actual focal length of the lens on superzooms is unlikely to be stated in the advertising blurb. It's far more likely you'll see this camera advertised as a 36-432mm equivalent focal length camera. When it say this then 100mm equivalent means that the field of view at 100mm equivalent is the same as a 100mm lens on a 35mm camera.

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Old Mar 3, 2008, 1:34 PM   #10
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try again; it is easy for the compacts; adjustments have been done, focal lengths quoted are "adjusted" and standardised, which means that 35-350 10x zoom lens will give the same magnification on any compactcamera, and for that matter the 350 zoom would give a 7X magnification considering that 50mm would be the "standard " focal length (as per old film slr)



for dslr no standardisation has been done and really as slr users are clever enough they have to work it out for themselves takinginto account lens attributes and sensor sizes??



is that right??
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