Focal length / xx times zoom equivalents

[BADGER.BRAD]

Hello all,

Am I over simplifying this but is a 100mm focal length the same as 10mm with a 10x zoom ?

 

[Box Brownie]

Hello all,

Am I over simplifying this but is a 100mm focal length the same as 10mm with a 10x zoom ?

Yes & No

Zoom IMO refers to a lens with a variable Focal Length.

In the example you pose, the 100mm FL is 10x the 10mm FL. It is a multiplication factor not in construction terms a "zoom" figure.

 

[clairewilliams]

Yes & No

Zoom IMO refers to a lens with a variable Focal Length.

In the example you pose, the 100mm FL is 10x the 10mm FL. It is a multiplication factor not in construction terms a "zoom" figure.

can you explain in detail i didn't get it. sorry

 

[Garry Edwards]

Yes & No

Zoom IMO refers to a lens with a variable Focal Length.

In the example you pose, the 100mm FL is 10x the 10mm FL. It is a multiplication factor not in construction terms a "zoom" figure.

can you explain in detail i didn't get it. sorry

A variable focal length lens (zoom lens) is simply a lens on which the focal length can be changed. A 10x zoom might range from 10 - 100mm, or 100 - 1000mm, as examples.

In practical terms, a zoom lens allows you to magnify the image without changing your position relative to the subject, i.e. you change the magnification by moving your fingers instead of moving your feet. Using a zoom lens doesn't affect the exposure but it does affect the perspective because perspective is governed by the distance from the lens to the various different parts of the image and not by the focal length of the lens.

 

[Nod]

Surely the perspective stays the same if you stay in the same spot? The angle of view will change as you zoom but the perspective stays the same.

 

[Garry Edwards]

Surely the perspective stays the same if you stay in the same spot? The angle of view will change as you zoom but the perspective stays the same.

That's correct.

Using a zoom lens doesn't affect the exposure but it does affect the perspective because perspective is governed by the distance from the lens to the various different parts of the image and not by the focal length of the lens.

Moving your own position closer to the subject or further away is the factor that affects the perspective. But although zooming with the lens instead of zooming with the feet has zero theoretical effect on the perspective, it does have a practical effect because the perspective is different to what it would be if you zoomed with your feet

 

[clairewilliams]

A variable focal length lens (zoom lens) is simply a lens on which the focal length can be changed. A 10x zoom might range from 10 - 100mm, or 100 - 1000mm, as examples.

In practical terms, a zoom lens allows you to magnify the image without changing your position relative to the subject, i.e. you change the magnification by moving your fingers instead of moving your feet. Using a zoom lens doesn't affect the exposure but it does affect the perspective because perspective is governed by the distance from the lens to the various different parts of the image and not by the focal length of the lens.

Ohh, thanks for explaining

 

[clairewilliams]

but when I zoom in the image gets pixelated, so is their a solution for that or I have to get some equipment

 

[Box Brownie]

but when I zoom in the image gets pixelated, so is their a solution for that or I have to get some equipment

The discussion is about optical zoom lenses vs fixed focal Length lenses.

where you mention pixelation I surmise you are referring to digital zoom (in camera cropping of the image area on the sensor) and that is whole IMO different subject.

If you stated what camera you are using it help others to help you.

 

[ShinySideUp]

For the OP, if you are using digital zoom:

Optical/Digital zoom

 

[sphexx]

It’s so annoying that the original use of “zoom” has been changed and nothing I think has been put in its place And people coming to fresh now seem to fing it a confusing concept so I’m not sure anything’s been gained.

Much the same with apertures — large or small clearly always referred to the size of the hole the light was going through but sometimes now people seem to be referring to the (apparent) size of the numbers of the f-stops.

 

[Garry Edwards]

It’s so annoying that the original use of “zoom” has been changed and nothing I think has been put in its place And people coming to fresh now seem to fing it a confusing concept so I’m not sure anything’s been gained.

Much the same with apertures — large or small clearly always referred to the size of the hole the light was going through but sometimes now people seem to be referring to the (apparent) size of the numbers of the f-stops.

I agree, "digital zoom" is really just cropping, throwing away quality. It isn't too bad with some devices such as high-end iPhones, but is basically just deceptive marketing.
The misunderstanding of large and small aperture is basically just down to ignorance - if for example people understood what the 'f/' in f/16 actually means they would avoid confusing themselves. And of course, it doesn't help that modern technology has prevented most people from actually seeing a lens aperture in anything but its wide-open position.

 

[ShinySideUp]

Thinking on the f stop thing, it has crossed my mind that for some reason, I have never been confused by it. I think it might be down to some sort of synaesthesia in that lower numbers appear to be nearer and bigger in my mind's eye, so f2 really seems much bigger than f16, which I see as being quite small and far away, which of course equates to the relative sizes of the apertures concerned. Weird.

 

[woof woof]

If you get brain fade (and we all do) the easy (maybe) way to remember that low numbers equal a big aperture hole is that that you can determine the size of the hole by dividing the focal length by the aperture.

eg.
A 50mm lens/focal length set to f2 has a 25mm aperture.
A 50mm lens/focal length set to f16 has a 3.125mm aperture.
Therefore a focal length divided by a small f number always gives a bigger aperture than a focal length divided by a larger f number.

 

[ShinySideUp]

That doesn't seem to work. If I have a 400mm f4 lens then by this logic the aperture is 114mm or nearly 4 1/2 inches!

 

[woof woof]

That doesn't seem to work. If I have a 400mm f4 lens then by this logic the aperture is 114mm or nearly 4 1/2 inches!

Don't blame me

Google it

It's the aperture as viewed from the front of the lens and I believe... as a projection...

You really need to Google it and even then you'll probably need your fingers crossed to understand it

Here's one link...

Relation of F-numbers to the Aperture – Exposure Therapy

An explanation for the confusing inverse numerical relationship between f-numbers (f-stops) and aperture size.

exposuretherapy.ca

 

[sphexx]

I agree, "digital zoom" is really just cropping, throwing away quality. It isn't too bad with some devices such as high-end iPhones, but is basically just deceptive marketing.
The misunderstanding of large and small aperture is basically just down to ignorance - if for example people understood what the 'f/' in f/16 actually means they would avoid confusing themselves. And of course, it doesn't help that modern technology has prevented most people from actually seeing a lens aperture in anything but its wide-open position.

my first camera being a roll film folder meant that all the functions and how they related were blindingingly obvious. I don’t think I ever heard the term”exposure triangle” it just got absorbed.

my first exposure meter was that Johnson plastic disc calculator that I fancy might be adapted as a learning tool these days. My heart bleeds for anyone going from smart phone to “real” camera these days unless they do extensive reading first.

Heres the Johnson thingy used with a digicam:

View: https://youtu.be/B0SFrOuXcfw


I don’t think it will help with zoom thing though so somewhat OT .

 

[ShinySideUp]

Don't blame me

Google it

It's the aperture as viewed from the front of the lens and I believe... as a projection...

You really need to Google it and even then you'll probably need your fingers crossed to understand it

Here's one link...

Relation of F-numbers to the Aperture – Exposure Therapy

An explanation for the confusing inverse numerical relationship between f-numbers (f-stops) and aperture size.

exposuretherapy.ca

I looked, I'm not a lot nearer if I'm honest , but then I don't have to be able to design a car to be able to drive it so I think I'll just leave it to the light nerds and move on.

 

[huffy]

When I have explained the F numbers for aperture to folks I suggest they replace the F with the number 1 so it then becomes a fraction.

I.e.F16 (1/16) is smaller than F4 (1/4)

 

[Garry Edwards]

When I have explained the F numbers for aperture to folks I suggest they replace the F with the number 1 so it then becomes a fraction.

I.e.F16 (1/16) is smaller than F4 (1/4)

Good idea. But don't confuse yourself by using the wrong terminology, which just complicates things.
F = focal length
f = lens aperture
Therefore, f/ = F/f

So, if F=100 you have a 100mm lens
if it's set to f/11 the actual (or effective) lens aperture is f9, or 9mm.

I always think it easier to think in terms of f rather than f/, because if we know the actual (effective) aperture then it's easy to calculate the depth of field (which some people wrongly call the depth of focus )

 

[clairewilliams]

The discussion is about optical zoom lenses vs fixed focal Length lenses.

where you mention pixelation I surmise you are referring to digital zoom (in camera cropping of the image area on the sensor) and that is whole IMO different subject.

If you stated what camera you are using it help others to help you.

currently, I don't have a camera currently i am using pixel 7 but planning to get one. I looking to get this one https://sg.canon/en/consumer/eos-20...uct?category=photography&subCategory=dslr-eos

 

[swanseamale47]

currently, I don't have a camera currently i am using pixel 7 but planning to get one. I looking to get this one https://sg.canon/en/consumer/eos-20...uct?category=photography&subCategory=dslr-eos

Thats a decent camera, my other half has a similar model and I'm quite impressed by it.

 

[AndrewFlannigan]

If I have a 400mm f4 lens then by this logic the aperture is 114mm or nearly 4 1/2 inches!

That's entirely correct. An f4 / 400mm is a big lump of glass and metal.

 

[RichardC27]

That doesn't seem to work. If I have a 400mm f4 lens then by this logic the aperture is 114mm or nearly 4 1/2 inches!

A 400mm f/4 has an aperture opening 100mm wide at f/4. 400 / 4 =100

A 400mm f/2,8 is one stop faster but has an aperture of 142.9mm wide open, which is why big tele primes are so massive.

 

[clairewilliams]

Thats a decent camera, my other half has a similar model and I'm quite impressed by it.

oh wow that's nice, so should for this one or do you have any other suggestion. and what about lenses which lens should i get

 

[Box Brownie]

oh wow that's nice, so should for this one or do you have any other suggestion. and what about lenses which lens should i get

Re: lenses
Many cameras come as kits with a short zoom such an 18-55mm to quite literally 'get you started'.

It will be a learning curve so IMO start with the kit lens to learn how to use the camera and your camera technique. Only then consider, for what & why you might need another/other lenses???

All the best with your photographic journey

 

[ShinySideUp]

A 400mm f/4 has an aperture opening 100mm wide at f/4. 400 / 4 =100

A 400mm f/2,8 is one stop faster but has an aperture of 142.9mm wide open, which is why big tele primes are so massive.

I think it needs to be clarified that when mentioning 'aperture' size, it is not the physical width of the opening in the lens as might be measured with a ruler. After this discussion, I'm no longer quite sure exactly what it is a measure of.

 

[Garry Edwards]

I think it needs to be clarified that when mentioning 'aperture' size, it is not the physical width of the opening in the lens as might be measured with a ruler. After this discussion, I'm no longer quite sure exactly what it is a measure of.

The effective or actual aperture size IS the diameter of the opening.
The f number (f/) is F (the focal length of the lens) divided by f (the diameter of the opening, e.g. 100mm focal length divided by 10mm aperture = f/10

 

[RichardC27]

I think it needs to be clarified that when mentioning 'aperture' size, it is not the physical width of the opening in the lens as might be measured with a ruler. After this discussion, I'm no longer quite sure exactly what it is a measure of.

It is the physical width of the opening as measured with a ruler. Aperture is a fraction of focal length, which is why it is correctly written as f/4. As in, aperture = focal length divided by 4. f/2.8 is focal length divided by 2.8. This is why larger apertures have smaller numbers, as you're dividing the focal length by a smaller number, so giving a wider opening. An aperture of f/1 is the same as the focal length. This is why big telephoto lenses top out at f/4 or f/2.8. A 400mm f/1 lens would have an aperture 400mm wide and you'd need a truck to mount it on.

Bare in mind the aperture is quite some way into the lens so the front element will be larger than the aperture size.

 

[AndrewFlannigan]

Bare in mind the aperture is quite some way into the lens...

The question is: who are you "baring in your mind" and do you have permission so to do?

 

[clairewilliams]

Re: lenses
Many cameras come as kits with a short zoom such an 18-55mm to quite literally 'get you started'.

It will be a learning curve so IMO start with the kit lens to learn how to use the camera and your camera technique. Only then consider, for what & why you might need another/other lenses???

All the best with your photographic journey

oh thank you so much buddy☺

 

[swanseamale47]

The C

oh wow that's nice, so should for this one or do you have any other suggestion. and what about lenses which lens should i get

The Canon 18-55mm kit lens (or the 18-135mm) are both good starter lens. Extra lens really depend on what your going to photograph, eg close up is easier with a macro lens, birds a telephoto. So I'd suggest you have a think about what takes your fancy photo wise, and work from there.
I've just realised I know a Claire Williams, do you work for an insurance company by any chance?

 

[wiltw]

Thinking on the f stop thing, it has crossed my mind that for some reason, I have never been confused by it. I think it might be down to some sort of synaesthesia in that lower numbers appear to be nearer and bigger in my mind's eye, so f2 really seems much bigger than f16, which I see as being quite small and far away, which of course equates to the relative sizes of the apertures concerned. Weird.

Because the f/number is the DENOMINATOR of a fraction...
f/2 is 1/2 * FL...the aperture diameter is 1/2 of the FL
f/4 is 1/4 * FL...the aperture diameter is 1/4 of the FL
f/22 is 1/22 * FL...the aperture diameter is 1/22 of the FL

 

[wiltw]

To the OP question, a 10X zoom is harder (more exsensive) to correct optically for all the parameters of performance than a 3X zoom
When used wide open, a 3X zoom typically will have less lens barrel/pincushion distortion at its shortest FL, it will have less vignetting wide open at its shortest FL, it will likely have better contrast in general (due to fewer optical-air surfaces in the design)

High zoom range designs more often are wide-to-tele ramge designs and have more complex optical designs than only-tele FL zoom range lenses