question on zoom range


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drewdam

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Jun 18, 2005
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#1
hi,

am using a FZ20 now, which has a zoom range of 36mm-432mm, can i say that the dslr lens with 80-200mm is the 1:1 ratio to my FZ20 200mm zoom? or should i say at 200mm is about 5x the optical range?

reason for this is i am used to such the long range and if i will to go into dslr..i need to work up the budget..:sweat:
 

Zaknafein

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#3
drewdam said:
hi,

am using a FZ20 now, which has a zoom range of 36mm-432mm, can i say that the dslr lens with 80-200mm is the 1:1 ratio to my FZ20 200mm zoom? or should i say at 200mm is about 5x the optical range?

reason for this is i am used to such the long range and if i will to go into dslr..i need to work up the budget..:sweat:
u have to take the crop factor of the DSLR body into consideration too.
 

Apr 12, 2005
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#4
drewdam said:
hi,

am using a FZ20 now, which has a zoom range of 36mm-432mm, can i say that the dslr lens with 80-200mm is the 1:1 ratio to my FZ20 200mm zoom? or should i say at 200mm is about 5x the optical range?

reason for this is i am used to such the long range and if i will to go into dslr..i need to work up the budget..:sweat:
1) 432mm/36mm =12x

That's why they call it 12x optical zoom.

2) For the FZ20, the actual focal length at 12x optical zoom (i.e. 35mm format equivalent of 432mm) is only 72mm.

But because of FZ20's small 1/2.5" sensor, the subjects in the frame appear as if they're taken at 432mm focal length on a full frame 35mm format sensor/film.

That's why the 35mm format equivalent of the FZ20 at max. focal length is 432mm.

3) To have the same subject sizes in the DSLR's frame as the FZ20 at 12x optical zoom, the subject sizes on the DSLR frame should be as if they're taken at 432mm focal length on a full frame 35mm format sensor.

This means that

a) if the DSLR has a full frame sensor, then the lens used must have at least 432mm focal length to match the FZ20's subject sizes on the frame at 12x optical zoom.

b) if the DSLR has an APS sized sensor (which most DSLRs currently have), its sensor frame is actually about 1.5 times smaller (which is commonly called "crop factor", as measured by both length and breath are approximately 1.5x shorter and area size therefore 2.25 times smaller) than a full frame. Therefore the focal length necessary to achieve the same subject sizes on the smaller sensor as 432mm lens on a full frame = 432/1.5 = 288mm.

This means that 288mm would also be the focal length for a DSLR with a crop factor of 1.5 to achieve the same subject sizes as the FZ20 at 12x optical zoom.

Crop factors range from 1.4-1.6 for most DSLRs with APS-sized sensor.

So the approximate SLR lens focal length you're looking at to get the same subject sizes as the FZ20 at 12x optical zoom would be about 300mm.

c) For the reasons above, different cameras capture different levels of details at the same 35mm format equivalent focal length because the actual focal length used are different for different sensor sizes. (72mm for FZ20, about 288mm for APS-sized sensor DSLR, and 432mm for a full frame sensor DSLR or film camera).

Summary : You should be looking at 300mm lens if yours is an APS-sized sensor DSLR.

Hope the above answers your question.
 

sumball

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Learnt something new today. Thanks!
 

drewdam

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#6
hi Clockunder,

wo...tks for taking time to explain....look like i have to part more $ to go into dslr...look like the resist of BBB is tough tho.
 

Apr 12, 2005
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#7
drewdam said:
hi Clockunder,

wo...tks for taking time to explain....look like i have to part more $ to go into dslr...look like the resist of BBB is tough tho.
Yes, going into DSLR is not as cheap as first thought.

Just to add to what has been posted earlier :

How 72mm on the FZ20 is equal to 432mm equivalent on the 35mm format?

The sensor size of the FZ20 is 1/2.5" (a form of specification which doesn't actually mean that it has 1/2.5" = 1.02cm measurement) and the actual measurement is

5.76mm x 4.29mm

Therefore its sensor's diagonal measurement is sqrt(5.76^2 + 4.29^2) = 7.182 mm

For the 35mm format full frame, the measurement is

36mm x 24mm

==>diagonal = sqrt(36^2 + 24^2) = 43.3mm

This means that the sensor size of the FZ20 is 7.182/43.3 = about 1/6 of the 35mm format.

Images taken at 72mm on the FZ20 will therefore appear 6 times bigger (in terms of diagonals; FZ20 sensor is about 6x6= 36 times smaller in terms of area size) on the small 1/2.5" frame than on the much bigger 35mm format frame and so the 72mm focal length would give the same perception as being taken at 72 x 6 = 432mm on the 35mm format.

This explains why the max. 72mm focal length on the FZ20 is specified as "432mm (35mm format equivalent)".

And of course, 72mm on a small sensor won't get your as much details as a longer focal length on a bigger sensor.
 

drewdam

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#8
does that translate a not so sharp image when shoot at 432mm on fz20 as compare to a lens with the same focal length or rather dull color image? am talking about pic out from cam and transfer to pc for viewing no PP at all.
 

MDZ2

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#9
drewdam said:
does that translate a not so sharp image when shoot at 432mm on fz20 as compare to a lens with the same focal length or rather dull color image? am talking about pic out from cam and transfer to pc for viewing no PP at all.
Actually, you do get as much detail as a DSLR with similar magapix count. except that each pixel of the smaller sensor are placed much closer than those on the bigger sensor, resulting in higher amounts of noise and distortion.
 

drewdam

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#10
MDZ2 said:
Actually, you do get as much detail as a DSLR with similar magapix count. except that each pixel of the smaller sensor are placed much closer than those on the bigger sensor, resulting in higher amounts of noise and distortion.
will the noise level improve if i select to shoot at 3m instead of 5m since small sensor squeeze in high magpix that usual cause more noise..
 

drewdam

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MDZ2 said:
Actually, you do get as much detail as a DSLR with similar magapix count. except that each pixel of the smaller sensor are placed much closer than those on the bigger sensor, resulting in higher amounts of noise and distortion.
will the noise level improve if i select to shoot at 3m instead of 5m since small sensor squeeze in high magpix that usually cause more noise..
 

ExplorerZ

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#12
Therefore its sensor's diagonal measurement is sqrt(5.76^2 + 4.29^2) = 7.182 mm

For the 35mm format full frame, the measurement is

36mm x 24mm

==>diagonal = sqrt(36^2 + 24^2) = 43.3mm

This means that the sensor size of the FZ20 is 7.182/43.3 = about 1/6 of the 35mm format.
agree with all the point u said except this. :nono:
by write you should calculate the area of the sensor and not diagonal size. which will be:
fz20: (5.76 x 4.29) = 24.7
full frame: (36 x 24) = 864

864/24.7 wich is ard 35x bigger!
but if talking about diagonal size den yes, its correct.
 

ExplorerZ

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#13
drewdam said:
will the noise level improve if i select to shoot at 3m instead of 5m since small sensor squeeze in high magpix that usually cause more noise..
3m? 5m? what do you mean? sensor size or focal length? :dunno: if sensor size from 3mm to 5mm with the same lens, would mean that you will get less "zoom" since it cropped lesser
 

obewan

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Feb 11, 2005
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#14
These technical information are really useful... :thumbsup:
But sometimes I'm still confuse. :confused:

Just a personal opinion.
Smaller sensor size is hardly an issue for a
prosumer camera, if we all shoot static object, don't do large print and under bright light
condition. Problems only arise when we shoot under dim dim condition,
we need to up the ISO and do large print.

Good if you are a technical person and understand these information.
No worry if you are a non technical person. Just enjoy photography
as it is, and take note of what you can see easily and not what you can't see. :bsmilie:
 

Apr 12, 2005
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#15
ExplorerZ said:
agree with all the point u said except this. :nono:
by write you should calculate the area of the sensor and not diagonal size. which will be:
fz20: (5.76 x 4.29) = 24.7
full frame: (36 x 24) = 864

864/24.7 wich is ard 35x bigger!
but if talking about diagonal size den yes, its correct.
Read the whole post instead of selectively. :nono: :bsmilie:

quote from my earlier post :

Images taken at 72mm on the FZ20 will therefore appear 6 times bigger (in terms of diagonals; FZ20 sensor is about 6x6= 36 times smaller in terms of area size) on the small 1/2.5" frame than on the much bigger 35mm format frame and so the 72mm focal length would give the same perception as being taken at 72 x 6 = 432mm on the 35mm format.
 

Apr 12, 2005
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#16
drewdam said:
does that translate a not so sharp image when shoot at 432mm on fz20 as compare to a lens with the same focal length or rather dull color image? am talking about pic out from cam and transfer to pc for viewing no PP at all.
Image shot with FZ20 at max. focal length 72mm (432mm on 35mm format equivalent) will have less details than one shot at 432mm on a full frame DSLR or at 288mm on a 1.5 crop factor DSLR because it will be of lower contrast, resolution and image fidelity (even assuming there is no difference in lens quality).

http://www.bobatkins.com/photography/digital/size_matters.html

Moreover, a larger sensor also means less noise. The space between photosites on a larger Sensor is more than those on a smaller sensor, thus less prone to noise.

About noise in photograhy : http://www.photoxels.com/tutorial_noise.html

In addition, longer focal length with the same F-stop aperture means that the actual physical size of the aperture used is much larger than a shorter focal length with the same F-stop aperture. This translates to a higher light (signal) to noise ratio.

So generally, the answer to your question is yes even if we exclude the effects of noise.

On top of that, you have the choice of attaching lens of better optics on a SLR
 

Apr 12, 2005
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#17
drewdam said:
will the noise level improve if i select to shoot at 3m instead of 5m since small sensor squeeze in high magpix that usually cause more noise..
Generally, noise are caused by :

a) thermal (long exposure)
and
b) low light signals vs interference

If shooting at 3m makes the subjects more illuminated than at 5m, then shooting at 3m would have lower noise than at 5m. So in most cases, the answer is yes.

But if shooting nearer doesn't improve the amount of light entering the camera or make it worse, the the answer is no.

The key is still the light condition.

Understand how noise is produced would help :
http://www.photoxels.com/tutorial_noise.html
 

MDZ2

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Feb 23, 2005
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#18
drewdam said:
will the noise level improve if i select to shoot at 3m instead of 5m since small sensor squeeze in high magpix that usual cause more noise..
I am assuming you are talking about the Panasonic FZ30 where the camera zoom is increased by reducing the sensor area used. If that is the case, there is no additional benefit since the sensor is still the same so the distance between pixel does not change.
On the other hand, if you are talking about reducing the resolution on the camera ie. changing setting from fine to normal, then perhaps it might reduce the noise level if alternate pixels are used thereby reducing the interference between pixels. Then again, you do loose image resolution which translate into jaged image when printed at larger sizes.
 

drewdam

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Jun 18, 2005
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#19
sori i din ask the question clearly...like wat MDZ2 said...just wonder any diff in noise for same condition if i will to select diff resolution but with same quality in jpeg selection?

oya, just want to know understand the noise in relation to CCD size n MP etc...at the end am enjoying my FZ20 ..just that thought of this quest about zoom before go into dslr...;(
 

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