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True 10X optical zoom?

 
 
Don
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      11-23-2003
I just purchased a Minolta Dimage Z1. I only had it for a day, it's
my first digital camera and I know nothing about photography, but I'm
already creating great pictures with it.

But I was curious as to why the 10X zoom is not quite as powerful as a
pair of 10X binoculars I have. At full optical zoom on the camera, I
get very crisp, clear pictures, but I noticed a sign off in the
distance that is not quite close enough in the printed picture to make
out the writing. The sign is readable through the binoculars, but
with the binoculars the sign appears to be much closer than the print
from the camera.

I used glossy photo paper and had the camera set to it's highest
resolution, printing at the same resolution, but this doesn't appear
to be a matter of resolution or clarity. The printed image really
doesn't appear to be as close as the binoculars.

I would assume a rating of 10X is standard on any instrument.
Am I missing something here or is that just the nature of a camera's
zoom as compared to the telescoping effect of other instruments.

Don
 
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Don
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      11-23-2003
I think I'll respond to my own posting. I should have mentioned that
the print I made was 4X6. Now I'm thinking that had I made a full
8X10 I may get a different perspective.

I'll give that a try before I start knocking the zoom capability of
this camera.

Don
 
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Andrew McDonald
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      11-23-2003
Don wrote:
> I would assume a rating of 10X is standard on any instrument.
> Am I missing something here or is that just the nature of a camera's
> zoom as compared to the telescoping effect of other instruments.
>
> Don

10x refers to the multiplication factor between the widest focal length
of the lens and the telephoto focal length.

Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
would be a 10X zoom lens.

I don't think there is any standard of magification between binoculars,
cameras or video cameras. I could be wrong but in my experience this
seems to be the case.

 
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Don
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      11-23-2003
Thank you. I did just print a 7.5X10 and that only opened a new can
of worms. I was originally going to purchase a 4MP camera, but
decided on the Minolta Z1 when the person helping me said a 3.2 pixel
will print fine up to 8X10 without losing any clarity.

That is not the case in my situation. The 4X6 is very clear, but the
larger printout loses a LOT of resolution.

Don


On Sun, 23 Nov 2003 22:41:37 GMT, Andrew McDonald <(E-Mail Removed)>
wrote:

>Don wrote:
>> I would assume a rating of 10X is standard on any instrument.
>> Am I missing something here or is that just the nature of a camera's
>> zoom as compared to the telescoping effect of other instruments.
>>
>> Don

>10x refers to the multiplication factor between the widest focal length
>of the lens and the telephoto focal length.
>
>Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
>would be a 10X zoom lens.
>
>I don't think there is any standard of magification between binoculars,
>cameras or video cameras. I could be wrong but in my experience this
>seems to be the case.
>


 
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Andy Hewitt
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      11-23-2003
Andrew McDonald <(E-Mail Removed)> wrote:

> Don wrote:
> > I would assume a rating of 10X is standard on any instrument.
> > Am I missing something here or is that just the nature of a camera's
> > zoom as compared to the telescoping effect of other instruments.
> >
> > Don

> 10x refers to the multiplication factor between the widest focal length
> of the lens and the telephoto focal length.
>
> Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
> would be a 10X zoom lens.
>
> I don't think there is any standard of magification between binoculars,
> cameras or video cameras. I could be wrong but in my experience this
> seems to be the case.


Actually, there is a standard. In traditional SLR photography they never
stated the zoom factor, only the focal length, or range of focal length.
As a rule it roughly equated that 1x zoom was about 50mm (it was
actually about 49mm). This offered a field of view roughly what you see
with the naked eye. Thus a 500mm lens was about 10x magnification. As
far as I know binoculars and telecopes work much the same way.

As far as digital cameras go, you are correct, they simply divide the
highest focal length by the lowest. However, the focal length of a
digital camera is not the same as it is with traditional optics, so you
have to convert them anyway.

You have to watch these things quite carefully now, as this kind of
false specification is popping up everywhere. I only found out a few
days ago that the dpi rating of a printer is in fact the *total' number
of pixels created by all of the print heads, so you have to divide the
dpi by the number of print heads to get the true dpi rating.


--
Andy Hewitt ** FAF#1, OSOS#5 - BMW K100RS 8v, Honda Concerto 16v
Windows free zone (Mac G3)
<http://homepage.ntlworld.com/ahewitt/index.htm> (last update 12.02)
 
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Jim Townsend
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      11-23-2003
Don wrote:

> I just purchased a Minolta Dimage Z1. I only had it for a day, it's
> my first digital camera and I know nothing about photography, but I'm
> already creating great pictures with it.
>
> But I was curious as to why the 10X zoom is not quite as powerful as a
> pair of 10X binoculars I have. At full optical zoom on the camera, I
> get very crisp, clear pictures, but I noticed a sign off in the
> distance that is not quite close enough in the printed picture to make
> out the writing. The sign is readable through the binoculars, but
> with the binoculars the sign appears to be much closer than the print
> from the camera.


Zoom is the difference between maximum and minimum focal length. It has
nothing to do with magnification.

In 35mm terms, your Z1 has an equivalent focal length of 38mm on the wide end
and 380mm on the telephoto.

So.. if you divide: 380mm max by 38mm min, you get 10. The maximum focal
length is 10 times more than the minimum. That's how the zoom is calculated.
Think of zoom as motion. (ie zooming in, zooming out). The 'X' in the zoom
rating shows how much the lens can -move- not magnify.

A fixed lens has no zoom at all since you can't move it.

Magnification gets tricky. In 35mm terms, (and only 35mm terms), a focal
length of about 50mm is thought to most closely approximate what our eyes see.
In other words 50mm gives you a magnification of exactly 1X..

By dividing the total focal length, you can roughly determine the magnification
of a lens. So your longest focal length (380mm) would provide 380/50= 7.6X
magnification.


 
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Mike O
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      11-23-2003
To expand, as I figure it, the 10x like he said refers to 10x 38mm in the
example Andrew gave. If your binoculers say 10x, its probably 10x
magnification...not a measurement you can compare.

Not positive but this sounds right to me at least :-}

Mike
-
"Andrew McDonald" <(E-Mail Removed)> wrote in message
news:BIawb.11555$(E-Mail Removed) hlink.net...
> Don wrote:
> > I would assume a rating of 10X is standard on any instrument.
> > Am I missing something here or is that just the nature of a camera's
> > zoom as compared to the telescoping effect of other instruments.
> >
> > Don

> 10x refers to the multiplication factor between the widest focal length
> of the lens and the telephoto focal length.
>
> Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
> would be a 10X zoom lens.
>
> I don't think there is any standard of magification between binoculars,
> cameras or video cameras. I could be wrong but in my experience this
> seems to be the case.
>



 
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Andy Hewitt
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Posts: n/a
 
      11-23-2003
Don <(E-Mail Removed)> wrote:

> Thank you. I did just print a 7.5X10 and that only opened a new can
> of worms. I was originally going to purchase a 4MP camera, but
> decided on the Minolta Z1 when the person helping me said a 3.2 pixel
> will print fine up to 8X10 without losing any clarity.
>
> That is not the case in my situation. The 4X6 is very clear, but the
> larger printout loses a LOT of resolution.


Hmmm, are you sure it's not your printer settings. I have some images I
printed onto A4 from my old Olympus C960z (a 1.3MP camera), and they are
certainly quite acceptable.

Don't forget you need to change the resolution of the image from the
72dpi screen resolution (which is what comes out of the camera) to
something like 300dpi for the printer.

--
Andy Hewitt ** FAF#1, OSOS#5 - BMW K100RS 8v, Honda Concerto 16v
Windows free zone (Mac G3)
<http://homepage.ntlworld.com/ahewitt/index.htm> (last update 12.02)
 
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Don
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Posts: n/a
 
      11-23-2003
Andy,

Interesting you should point that out regarding the pixels. As I
mentioned, my 7.5 X 10 printout lost a lot of resolution after the
salesperson told me this 3.2 pixel camera would not at that size.

But I just checked my printer's specs and see that although I shot the
scene at 2048 X 1764, my printer supports a maximum resolution of 4800
X 1200. Although the printer rates this as 5.8 MP, which is correct
and my camera is only 3.2 MP, the horizontal or vertical resolution
of the scene I shot is outside what my printer (Lexmark Z65) supports.
So I guess that problem is not with the camera, but with the printer.

Don

On Sun, 23 Nov 2003 23:08:05 +0000, http://www.velocityreviews.com/forums/(E-Mail Removed) (Andy
Hewitt) wrote:

>Andrew McDonald <(E-Mail Removed)> wrote:
>
>> Don wrote:
>> > I would assume a rating of 10X is standard on any instrument.
>> > Am I missing something here or is that just the nature of a camera's
>> > zoom as compared to the telescoping effect of other instruments.
>> >
>> > Don

>> 10x refers to the multiplication factor between the widest focal length
>> of the lens and the telephoto focal length.
>>
>> Thus a 35-70 zoom could be referred to as a 2x lens. A 38-380 lens
>> would be a 10X zoom lens.
>>
>> I don't think there is any standard of magification between binoculars,
>> cameras or video cameras. I could be wrong but in my experience this
>> seems to be the case.

>
>Actually, there is a standard. In traditional SLR photography they never
>stated the zoom factor, only the focal length, or range of focal length.
>As a rule it roughly equated that 1x zoom was about 50mm (it was
>actually about 49mm). This offered a field of view roughly what you see
>with the naked eye. Thus a 500mm lens was about 10x magnification. As
>far as I know binoculars and telecopes work much the same way.
>
>As far as digital cameras go, you are correct, they simply divide the
>highest focal length by the lowest. However, the focal length of a
>digital camera is not the same as it is with traditional optics, so you
>have to convert them anyway.
>
>You have to watch these things quite carefully now, as this kind of
>false specification is popping up everywhere. I only found out a few
>days ago that the dpi rating of a printer is in fact the *total' number
>of pixels created by all of the print heads, so you have to divide the
>dpi by the number of print heads to get the true dpi rating.
>
>
>--
>Andy Hewitt ** FAF#1, OSOS#5 - BMW K100RS 8v, Honda Concerto 16v
>Windows free zone (Mac G3)
><http://homepage.ntlworld.com/ahewitt/index.htm> (last update 12.02)


 
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Don
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Posts: n/a
 
      11-23-2003
Thanks. I get the idea now from these replies. I guess it's not the
problem I thought it was, then. I was comparing apples to whatever.
I'm perfectly happy with the amount of zoom and probably even more
satisfied now that you've all expalined that it isn't a shortcoming on
the part of the camera.



On Sun, 23 Nov 2003 17:08:59 -0600, Jim Townsend <(E-Mail Removed)>
wrote:

>Don wrote:
>
>> I just purchased a Minolta Dimage Z1. I only had it for a day, it's
>> my first digital camera and I know nothing about photography, but I'm
>> already creating great pictures with it.
>>
>> But I was curious as to why the 10X zoom is not quite as powerful as a
>> pair of 10X binoculars I have. At full optical zoom on the camera, I
>> get very crisp, clear pictures, but I noticed a sign off in the
>> distance that is not quite close enough in the printed picture to make
>> out the writing. The sign is readable through the binoculars, but
>> with the binoculars the sign appears to be much closer than the print
>> from the camera.

>
>Zoom is the difference between maximum and minimum focal length. It has
>nothing to do with magnification.
>
>In 35mm terms, your Z1 has an equivalent focal length of 38mm on the wide end
>and 380mm on the telephoto.
>
>So.. if you divide: 380mm max by 38mm min, you get 10. The maximum focal
>length is 10 times more than the minimum. That's how the zoom is calculated.
>Think of zoom as motion. (ie zooming in, zooming out). The 'X' in the zoom
>rating shows how much the lens can -move- not magnify.
>
>A fixed lens has no zoom at all since you can't move it.
>
>Magnification gets tricky. In 35mm terms, (and only 35mm terms), a focal
>length of about 50mm is thought to most closely approximate what our eyes see.
>In other words 50mm gives you a magnification of exactly 1X..
>
>By dividing the total focal length, you can roughly determine the magnification
>of a lens. So your longest focal length (380mm) would provide 380/50= 7.6X
>magnification.
>
>


 
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