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Topic: Super-zoom cameras (Read 2463 times) previous topic - next topic

Robin2

#30
Aug 28, 2017, 08:52 pm Last Edit: Aug 28, 2017, 08:53 pm by Robin2
I am pointing out that your 24-1000mm is not really 24-1000mm.  Read what I wrote about crop factors, focal lengths and sensor sizes again.  Your 24-1000mm is the optical equivalent of a 28-300mm on an entry or mid-range DSLR.  
As far as i can see my camera enlarges things (like a bird in a tree) by 42 times from one extreme of the lens to the other. I don't see how a 28-300 lens can do more than 10.7x

I do appreciate that the super zoom cameras use smaller sensors. If they did not the lens would have to be enormous.

Nevertheless, based on your comments,  if I can find a camera shop that will let me try a DSLR with a 28-300 zoom I will look at it.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

msssltd

#31
Aug 30, 2017, 10:40 am Last Edit: Aug 30, 2017, 10:49 am by msssltd
As far as i can see my camera enlarges things (like a bird in a tree) by 42 times from one extreme of the lens to the other. I don't see how a 28-300 lens can do more than 10.7x
We don't see images as much as we perceive them.  Due to perspective, how much bigger the bird appears will depend on how far you are from the tree and the focal length of the lens.

The magnification factor of a zoom lens is found by dividing the longest focal length by the shortest.
1000 / 24 = 41.66
300 / 28 = 10.71

Apart from making things appear bigger, moving the viewpoint closer by zooming in, narrows the field of view.  The magnification factor actually describes by how much the angle of view will be narrowed between the extents of focal length.  

Take a look at the specs of this Canon 28-300mm SLR lens.  The 10x magnification factor is apparent in the angle of view numbers.

Angle of view
Horizontal 65°-6°50'
Vertical 46°-4°35'
Diagonal 75°-8°15'

Other SLR zoom lenses are available and they all narrow by around their magnification factor between the extents of focal length.

Zooming in with your HS50 does not make the subject 42x bigger - It makes the scene 42x smaller.

Quote
I do appreciate that the super zoom cameras use smaller sensors. If they did not the lens would have to be enormous.
Modern zoom lenses bounce light back and forth between lens elements to increase the focal length, way beyond the physical dimensions.  The main purpose of reducing sensor size is to reduce the overall production cost.  Larger sensors require lenses with higher quality glass and more of it; both components are subject to very steep curves of diminishing yield in manufacturing.  

Where things get confused is with manufacturers cherry picking numbers 'equivalent' to 35mm film.

The sensor in my DSLR is 23mm (2/3 of 35mm) making the crop factor 1.5.   What that means is that if I take a picture on my DSLR, print it at 7 x 5, then compare it to the same scene, taken with the same lens on a 35mm film camera and printed at the same 7 x 5.  The print from my DSLR will look like the centre 2/3 of the scene was cropped out in the darkroom and magnified to fill the paper - With all the degradation that brings.  To produce a similar 'magnified' image on the 35mm film camera without cropping and without the degradation, I would have to use a lens with a focal length 1.5 times longer (75mm).

The 'equivalent' focal lengths of my 28-300mm are then
1.5 x 28 = 42mm
1.5 x 300 = 450mm

The sensor in your Fuji is 6.4mm; a relatively whopping crop factor of 5.41.  The equivalent focal lengths are quoted by the manufacturer (24-1000mm), so we have to divide by the crop factor to find the focal lengths which produce similar 'size' images on a 35mm film camera.
24 / 5.41 = 4.5mm
1000 / 5.41 = 185mm

To get the same images from my 1/3 smaller, 23mm DSLR sensor, the focal lengths are shorter again.
4.5 / 1.5 = 3mm
185 / 1.5 = 123mm

When I said your 1000mm was similar to my 300mm, before I looked up the crop factor for your EXR sensor, I was being rather kind.  We can tell from the short focal lengths that Fuji mounted the lens a darn site closer to the sensor than an SLRs rear element and it won't be as wide the numbers suggest.


Quote
Nevertheless, based on your comments,  if I can find a camera shop that will let me try a DSLR with a 28-300 zoom I will look at it.

...R
Excellent news.  If there is a London Camera Exchange nearby, their staff are usually clued up and don't mind customers handling the goods.  Try to order your priorities first, size, weight, features etc.  You may still decide you prefer a bridge camera but at least you will have given the DSLR a chance.

For all the maths there is no substitute for picking up a camera and having a go with it.  I took a couple of snaps with my 28-300mm Sunday evening with this thread in mind.  Not great shots but I happen to know the navigation mark highlighted is around 1 mile away.

28mm


300mm



Robin2

I crudely measured the yacht in the two pictures on my PC and the small one is about 5mm long and the big one about 47mm which is close enough to the expected 1:10.7

I would expect it to be about 200mm with my 1:42 lens - i.e. it would not fit within the bounds of the image which is about 126mm wide on my PC.

Nice picture.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

Robin2

#33
Aug 30, 2017, 01:21 pm Last Edit: Aug 30, 2017, 01:30 pm by Robin2
Just thought I would share some pics to illustrate the Fuji HS50 zoom. The lighting was poor and the air was not clear and it was starting to rain, so all done in a hurry. (The numbers are the equivalents for a 35mm camera)

24mm


300mm


1000mm



...R
Two or three hours spent thinking and reading documentation solves most programming problems.

travis_farmer

I would be more impressed if i could read the tire size on that white car ;)

but seriously, both cameras put my Canon PowerShot A560 (5.8 - 23.2mm) to some serious shame. but then i have no current need for super zoom. though it would be neat to have a telescope with a camera mount. i have always been fascinated with space.
but then, the subjects of my camera tend to be a lot closer, like houses i am working on, or kitchen cabinets i have built. no real need for super zoom.

~Travis
Current Obsession: My server rack cooler, and my CNC Router
Check out my website, i have my own under-used forum on my hobby server.

Robin2

#35
Aug 30, 2017, 04:05 pm Last Edit: Aug 30, 2017, 04:08 pm by Robin2
I would be more impressed if i could read the tire size on that white car ;)
Maybe you can figure out the make of car from this and then the tyre size  :)



This is cropped directly from the camera image with no other enhancement. For the previous images I reduced the image size to 1280x960

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

MorganS

Quote
Modern zoom lenses bounce light back and forth between lens elements to increase the focal length, way beyond the physical dimensions.
No, that would be a mirror lens. That type of lens is relatively rare and almost always a fixed focal length, not a zoom. They are also very light, as well as compact as there's only 2 mirrors and the glass elements are always small and light. (The most common optical layout does have glass at the big end, but it's not thick.)

Telephoto lenses are never as long as the nominal focal length. The focal length refers to an idealised lens which can never exist in the real world. Multiple glass elements always compress the physical length of the lens to be less than the focal length.

You can get "reverse telephoto" lenses which are longer than their focal length. That's a technique used for short focal lengths like 16mm or less, where you can't actually put the lens 16mm away from the image sensor, due to the swinging mirror in the SLR. Ditching the mirror makes the lenses so much more compact and efficient than the equivalent SLR lens.
"The problem is in the code you didn't post."

Robin2

#37
Sep 08, 2017, 04:23 pm Last Edit: Sep 08, 2017, 04:23 pm by Robin2
Your 24-1000mm is the optical equivalent of a 28-300mm on an entry or mid-range DSLR.  
As promised I did look at a DSLR camera with a 300mm lens when I got the opportunity and, as I expected, its magnification was very much less than my 42x Fuji HS50.

After a lot of deliberation I decided to buy a Nikon Coolpix P900 which has the daddy of all zooms at 83x. Just got it yesterday but so far I am delighted with it.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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