Optical zoom


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wheek

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Guys, I notice Canon Ixus 400 says their 3x optical zoom is 36-108mm in 35mm equivalent while Kodak DX6400 says their 4x optical zoom is 33-132mm.

I know this sounds dumb, but what's the diff? I mean Canon's lowest is 36mm wherelse Kodak's is 33mm but what does this mean? With Kodak I have wider view? Noob here!!

Also, is there much difference between 108 & 132mm? I mean, on one hand I'm tempted by the fact that Kodak's has more zoom. I know some ppl would say if I'm that concerned about zoom, then get those 10x optical models but too ex lah. So I'm wondering if there a noticeable difference between 108 & 132mm?
 

justarius

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#2
Another newbie here, but I think that a few mm differences in the focal length matters a LOT more in the short end then at the long end. The angle of view between a 28mm, 24mm and 20mm is very obvious. However the difference between 100mm, 105mm is not at all big.

Its up to you whether you want a bit more reach at the long end, or want to capture more stuff in a shot at the short end...
 

wheek

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justarius said:
Another newbie here, but I think that a few mm differences in the focal length matters a LOT more in the short end then at the long end. The angle of view between a 28mm, 24mm and 20mm is very obvious. However the difference between 100mm, 105mm is not at all big.

Its up to you whether you want a bit more reach at the long end, or want to capture more stuff in a shot at the short end...
Ok I understand that 100mm & 105mm ain't much diff but over here we're talking about 108 versus 132 which is 24mm difference.
 

patch17

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hmmm... if you really want to see the difference 24mm can make, borrow an SLR with a 50mm and 24mm lens. look through with each lens and judge for yourself. :D
 

wheek

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patch17 said:
hmmm... if you really want to see the difference 24mm can make, borrow an SLR with a 50mm and 24mm lens. look through with each lens and judge for yourself. :D
Alamak! Looks like I'll have to go to the shop & ask for both digicams, zoom to max optical then see the diff liao.
 

yaoxing

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wheek said:
Alamak! Looks like I'll have to go to the shop & ask for both digicams, zoom to max optical then see the diff liao.
Try Canon's website where there's a "demo" of how differently images look when shot with different focal length. Not a very good demo but you can see roughly how focal lengths affect your images.
 

Nov 13, 2003
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hai yah...
juz go down to the shop and see see lah...
maybe also try other models, see which u like the feel of etc...
maybe u end up with a diff camera in the end :)

FYI, the shops with good reputation here are
Alan photo
Cathay Photo
MS color

u can e-quote them also, in case u scared kena cheated...
 

Ah Pao

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The only practical reason why consumer digicam optical zooms are quoted in factors of x-zooms is because they have different sensor sizes. The actual focal length of the lens on these cameras make little sense when taken out of context from the sensor size.

Read:
http://www.dpreview.com/learn/Glossary/Optical/Focal_length_multiplier_01.htm

Basically, you need to take in account the sensor size (which most of the time the salesman will not know). Anyway, the best is still to go down and play with the cameras and see the difference for yourself. Some may appreciate the wider angle, while others may prefer the longer telephoto. You decide.
 

chriszzz

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Ah Pao said:
The only practical reason why consumer digicam optical zooms are quoted in factors of x-zooms is because they have different sensor sizes. The actual focal length of the lens on these cameras make little sense when taken out of context from the sensor size.

Read:
http://www.dpreview.com/learn/Glossary/Optical/Focal_length_multiplier_01.htm

Basically, you need to take in account the sensor size (which most of the time the salesman will not know).
That's true, that's why most digicams also state their focal lengths in 35mm equivalent so its something we can relate to easily. So 50mm (35mm equivalent) on the IXUS 400 will be equivalent to the 50mm on the Kodak in terms of FOV, although DOF might be slightly different depending on the actual focal length. But your average newbie is not going to understand or care about this, and it won't be much diff anyway since it's probably something like 12mm vs 13mm (actual focal length ) for cameras in the same "category".
 

espn

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#10
108 vs 132, the difference is 24mm in the focal length, not the wideness anymore.

The link provided is only with reference to the DSLRs CCD sizes.
 

Ah Pao

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#11
chriszzz said:
...So 50mm (35mm equivalent) on the IXUS 400 will be equivalent to the 50mm on the Kodak in terms of FOV, although DOF might be slightly different depending on the actual focal length....
Hmm, I don't know how to express myself here what I mean, but it's the same with the DSLR's "focal length multipler" or "crop factor" issue. The lens' focal lengths are absolute, so IF the two cameras are using different-sized sensors, it makes no sense comparing their zoom power and their FOV based on the lens' focal lengths.

You don't see extreme wide angles on camera phones with a 3.5mm focal length, do you? :)

Ah, why am I dwelling on these technicalities? Just go down to the shop, try out both cameras, and see which one fits your needs better!
 

espn

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#12
By right, zoom has no definite meaning and is useless in comparing as what ah Pao has mentioned.

Just like 70-200 = 2.8x zoom, and a 28-105 = 3.7x zoom. This doesn't mean that the 28-105 has a longer zoom, right?

Similarly in DC, the total focal range I feel would be more important then <X>x zoom, some start from 28mm, like the CP5400 so 4x = 112mm, compared to a normal 4x zoom of 35mm = 140mm.
 

chriszzz

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#13
Ah Pao said:
Hmm, I don't know how to express myself here what I mean, but it's the same with the DSLR's "focal length multipler" or "crop factor" issue. The lens' focal lengths are absolute, so IF the two cameras are using different-sized sensors, it makes no sense comparing their zoom power and their FOV based on the lens' focal lengths.
Which is why you don't compare on actual focal lengths alone, but on the 35mm "equivalent", which is used by basically all consumer digicams. 35mm equivalents provide a convenient frame of reference since most people are familiar with it.

The 35-105mm, etc are all 35mm "equivalents". The actual would be something like 7mm-25mm or so, which are useful only for calculating DOF, but not FOV unless you know the sensor size, which would be beyond most newbies.
 

wheek

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Wow this is getting complicated! Think I'll just put the 2 cameras side by side, zoom to the max of their optical zooms then compare the diff.
 

TME

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#15
I thought wheek was asking if there was an actual difference in the numbers he saw for both cameras 33mm vs. 36mm and 108mm vs. 132mm? His question didn't seem answered.

Anyway, I thought I'll ask a question too, which also help wheek. If the digicam's focal lengths are converted into 35mm equivalents, does the conversion take into consideration the sensor size? Can we do a straight compare between 35mm (converted) focal lengths for a digicam? Or is the sensor size yet to be factored in?

Cos if the sensor size is already factored in, then wheek, 33mm is significantly wider than 36mm while 132mm is quite a bit longer than 108mm. If the sensor size is not factored in, then I dun know how to compare also lar..... that will be a bit too technical.... :)
 

wheek

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TME said:
I thought wheek was asking if there was an actual difference in the numbers he saw for both cameras 33mm vs. 36mm and 108mm vs. 132mm? His question didn't seem answered.

Anyway, I thought I'll ask a question too, which also help wheek. If the digicam's focal lengths are converted into 35mm equivalents, does the conversion take into consideration the sensor size? Can we do a straight compare between 35mm (converted) focal lengths for a digicam? Or is the sensor size yet to be factored in?

Cos if the sensor size is already factored in, then wheek, 33mm is significantly wider than 36mm while 132mm is quite a bit longer than 108mm. If the sensor size is not factored in, then I dun know how to compare also lar..... that will be a bit too technical.... :)
hehe! Yeah ur right! :D I know that not all 3x optical zooms are the same. I have seen several 3x optical zoom models with 35mm equivalent of 105, 108, 111, 114, etc. Now if the 2 digicams I am considering are 105 & 108, I wouldn't lose too much sleep over it since the diff is barely anything.

The thing is now I'm considering a 4x optical zoom model which has 35mm equivalent of 132mm and a 3x optical zoom model which as 35mm equivalent of 108mm. The shop claims 4x & 3x optical zoom not much difference. Which a noob like me might agree with. But when u look at the 35mm equivalent, there is quite a bit of difference between 108mm & 132mm.

And basically that was all I was asking. Whether in reality there's much diff or not. I know the easiest way is to go to the shop to try both, but since few shops are open, I thought I'd just try my luck here first.
 

chriszzz

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#17
wheek said:
The thing is now I'm considering a 4x optical zoom model which has 35mm equivalent of 132mm and a 3x optical zoom model which as 35mm equivalent of 108mm. The shop claims 4x & 3x optical zoom not much difference. Which a noob like me might agree with. But when u look at the 35mm equivalent, there is quite a bit of difference between 108mm & 132mm.

And basically that was all I was asking. Whether in reality there's much diff or not. I know the easiest way is to go to the shop to try both, but since few shops are open, I thought I'd just try my luck here first.
OK, there WILL be a diff, and it will be noticeable. Whether that diff bothers you will depend on your usage pattern. If you are a big user of the longer end of the range, then you'll probably want the longer reach. If you mostly shoot at the low-mid focal lengths and rarely use the longer end, you won't miss it at all. So ask yourself how you normally shoot. A look through your previous photos will tell you the answer. This is the same question those guys deciding between a 28-105 and 28-135 ask themselves.

Another point to consider is that your 2 cameras at the wide end are 33 vs 36mm. If you shoot wide often, you'll want the 33mm.
 

chriszzz

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TME said:
Anyway, I thought I'll ask a question too, which also help wheek. If the digicam's focal lengths are converted into 35mm equivalents, does the conversion take into consideration the sensor size?
Yes. It's already factored in to derive the 35mm "equivalent".
 

wheek

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chriszzz said:
OK, there WILL be a diff, and it will be noticeable. Whether that diff bothers you will depend on your usage pattern. If you are a big user of the longer end of the range, then you'll probably want the longer reach. If you mostly shoot at the low-mid focal lengths and rarely use the longer end, you won't miss it at all. So ask yourself how you normally shoot. A look through your previous photos will tell you the answer. This is the same question those guys deciding between a 28-105 and 28-135 ask themselves.

Another point to consider is that your 2 cameras at the wide end are 33 vs 36mm. If you shoot wide often, you'll want the 33mm.
Gee, then I guess the Kodak DX6440 is the one for me! I shoot mid focal most of the time but I would like to have that extra reach just in case the situation calls for it. So the 135mm would come in useful. And since the DX6440 has 33mm, I guess it'll come in useful for wide too. Best of both worlds I guess. :D
 

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