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I'm completely at sea with magnification, crop, zoom and telephoto, despite reading various info. I think it's because I'm not terribly scientific!

All I would like to know is, if I am shooting something which is very distant and I want to make it both larger and clearer, what kind of of zoom/telephoto/macro lens would I require? Macro to me means ladybirds on leaves within 50cm distance, but I could be wholly wrong on that!!

The following information is from comments by the O.P. to some of the answers below.

To this answer:

I think I'm getting there now. I particularly liked your phrase 'the image of the bird reveals some details of its uniform." I'm trying to work out whether it is worth getting a telephoto lens or monocular to clip onto my mobile phone as I'm loath to buy a camera when my phone is always on hand. That's perhaps why I'm seeing x12 and x18, rather than mm.

To this answer:

I see now a simple distinction between telephoto and zoom. Thank you. As you'll see from my edited title, I'm actually thinking of getting either a clip on lens or a monocular for my mobile (Galaxy S7). The question about clarity is really that I am forever photographing birds, squirrels, etc. and usually at some distance. My mobile does a great job at medium distance but zooming in just leaves me with a fuzzy blob where a bird should be.

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I'm completely at sea with magnification, crop, zoom and telephoto

Lenses are described in terms of focal length, and all you really need to know about focal length is that shorter focal lengths give a wide angle view, and longer focal lengths give a very narrow view. That is, a wide angle lens (again, short focal length, like 10mm or 20mm) packs most of what you see before you into the image; a lens with longer focal length (say, 200mm or 400mm) puts a smaller part of the scene before you into the image, and since that part of the scene takes up the whole image, the objects that you can see in it obviously appear larger. So, long lenses make distant objects appear larger.

You're spot on with your understanding of macro lenses. Every lens has a minimum distance at which it can focus; macro lenses can focus closer than other lenses, so they're able to get good shots of small objects that are very close to the camera. The fact that a lens is a macro lens won't help at all with distant objects, but some macro lenses have long focal lengths and are therefore still good at shooting distant objects too.

The term telephoto really indicates a particular kind of lens design that allows the lens to be shorter than it's focal length. Long focal length lenses used for photography are most often telephoto lenses, though, and so telephoto is often used to mean any long focal length lens, i.e. the opposite of "wide angle."

A zoom lens is just a lens that has variable focal length, so that you can change the angle of view. There are wide angle zooms that go from, say, 8mm to 15mm; mid-range zooms that cover a relatively wide 24mm to relatively long 70mm or 105mm; and telephoto zooms that cover distances like 70mm to 200mm, or maybe 100mm to 400mm. The fact that a lens is a zoom doesn't necessarily mean that it has a long focal length, but the long lenses that most people carry are more likely than not to be zoom lenses.

Lenses that have a single, fixed focal length are called prime lenses. Prime lenses have fewer optical variables, so they can be simpler, cheaper, and often sharper, but they lack the convenience of zooms.

if I am shooting something which is very distant and I want to make it both larger and clearer, what kind of of zoom/telephoto/macro lens would I require?

You'll need a lens with long focal length to make distant objects larger in your photo.

Clarity is a bit more complicated. If the photo is unclear because the atmosphere is hazy, there's not much that a lens can do to change that. But the lens does impact clarity in other ways. Some lenses produce sharper images than others because they have better optics.

If the objects in the photo move relative to the camera while you're taking the photo, you're going to get a blurred image. Long lenses are particularly sensitive to motion blur. Two lens features can help: large aperture, and image stabilization. A large aperture is able to gather more light, and that reduces the time needed to take the photo, so there's less time for camera or subject to move. Image stabilization is a feature that moves elements inside the lens to compensate for movement of the camera, which also gives you sharper images.

So, to make a distant object larger and clearer, you'll want a long lens with the best combination of optics, large aperture, and image stabilization that fits your budget.

The information above all applies to interchangeable lens cameras like DSLRs and mirrorless cameras. If you're looking at cameras that describe lenses like "18x zoom" or something like that, it's most likely a camera with a lens that can't be swapped for something else. The ideas above still apply, but the terminology is a bit different. Larger numbers, like "24x", indicate a longer focal length than smaller ones like "12x". You generally won't get any indication of aperture. Look specifically for optical zoom capability -- digital zoom just makes the pixels bigger, which will make the image seem less clear, not more.

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    One comment: as far as I'm aware the "proper" definition of a macro lens is one that supplies a 1x magnification or greater. In other words, the size of the image projected by the lens on the film/sensor is the same size as it is in reality, or larger. It's focus distance is completely irrelevant. – Shamtam Apr 15 '18 at 23:44
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    @Shamtam Yes that's the proper definition, but the OP is clearly looking for a more practical definition. Would you like to work out the focal length needed to create a 1:1 magnification from, say, 2 meters away? Distance may not be included in the formal definition, but it's unavoidable in practical terms. – Caleb Apr 16 '18 at 1:22
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    @Shamtam The vast majority of macro lenses only achieve 1:1 reproduction at their MFD (minimum focus distance). So focusing distance is supremely important to macro calculations. To get 1:1 reproduction the distance from the imaging plane to the lens' thin lens equivalent distance must be 2X the lens' focal length, and the subject must be 2X the lens' focal length past that distance and 4X the lens' focal length from the imaging plane. To get 1:1 at 10 meters would require a lens with a 2,500mm focal length and a 10 meter/10,000mm MFD! 1:1 at 100 meters would require a 25,000mm lens! – Michael C Apr 16 '18 at 5:18
  • "You generally won't get any indication of aperture." What? Yes, you will. All of those, for example, have the max aperture clearly written on the lens like every other lens does. Ditto for the focal length, for that matter. – user29608 Apr 17 '18 at 7:11
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The most layman's answer is: the larger the focal length the larger the reach. 200mm will be more "zoomed in" than 100mm and 300mm will be more reach than either.

How much reach you need is completely dependent on what you're shooting, how far away it is, and how much of the frame you want to fill with the subject.

Lenses in these longer focal ranges are called telephoto lenses or telephoto zooms.

Responding to your edit

add on lenses/monoculars for mobile phones

Well, this changes things a bit. I'm personally a huge fan of the Moment lenses. Build and image quality has been quite high when paired with a iPhone 6S. But, their telephoto attachment lens is 4x.

Now, there are lens attachments out there from other companies that offer more "zoom". I would recommend finding one that doesn't actually zoom, but it fixed (ie not 4x - 12x but rather, just 12x).

Zooms often sacrifice image quality for that functionality, so choosing a lens that is fixed means it'll likely have better IQ.

Outside of this though, I can't recommend much. There are many lens add-ons for phone cameras - some are very cheaply made. You'll have to go by the reviews and return policy and test some out to see if the image quality and focal length meet your needs.

Also keep in mind that phone cameras excel in really good lighting. Bad lighting is like a tax on the system and your image quality suffers. Adding an attachment lens is also a tax on the system. What I'm getting at is: adding an attachment lens in good lighting opens up your creative potential. Doing so in bad lighting is stacking one tax on another and will lead to doubly bad images.

  • Thanks Corey. Whenever I see lenses, they tend not to mention mm but say 60x40 or 18x. What should I be looking for if I were going for a 200, 300 or even 400mm? Many thanks... – Sarah Apr 15 '18 at 16:45
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    @Sarah 60x40? Are you looking at binoculars? Or telescopes? – osullic Apr 15 '18 at 21:31
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    @SarahEley: I don't know what lenses would say something like 60x40. When they say 18x that usually means the longest focal length is 18 times the shortest. That is somewhat helpful, but not a lot because you don't know what the shortest is. If it is a fixed lens camera the shortest tends to be about 25mm (35mm equivalent). A normal lens is considered to be 50mm (35mm equivalent) sometimes down to 35mm. Your 18x lens would then have a longest focal length of about 450mm. That is a serious telephoto and will do everything you would want except birds and long range sports – Ross Millikan Apr 16 '18 at 3:08
  • @SarahEley - see my edit. There's no point really in trying to compute the mm focal length from "12x" for a phone lens. Just realize that the higher the number, the greater the reach. 100mm is to 4x as 300mm is to 12x, for example. (It again comes back to - how much reach do you need?). Only you can really answer that. Though, we'll all try to help :-) – Hueco Apr 16 '18 at 17:23
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If you take a picture of a mountain or large animal at a distance, the size of that subject image might only be a few mm on the digital sensor or on the film (very small fractional magnification, which is a large reduction of reproduction). So you might use a zoom lens (longer focal length), to enlarge it to better fill the frame. Same visual size effect as moving closer. The longer the zoom lens focal length, the larger the image.

If subject were a tiny bug, then you have to get real close to magnify it enough. Regular lenses do not focus that close, so that would use a Macro lens, to allow focusing much closer, distance of only a few cm. A 1:1 macro lens means it can enlarge the bug (let's assume bug is 4 mm size) enough so that the image of the bug is the same 4 mm size. This is large for a picture of a bug. Then image is real life size, called 1:1 reproduction ratio.

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As you know, to see wildlife or sporting events, you pack binoculars. These nifty devices magnify making distance objects appear as if they were close. Most binoculars magnify about 6 X thru 8X, and some are available with lots more power. The parallel between binoculars and a camera’s telephoto lens is genuine. If at a horse race, the stallions are 1km (3,280 feet) away, dawn 8X binoculars, they now appear to be 125 meters (410 feet) away. Now you can see, some of the stallions are mares.

All cameras, based on the size of the image sensor (or film frame), have one lens focal length that the industry calls “normal”. This will be a focal length about equal to the corner-to- corner measurement of the senor. For the FX (full frame) this is 50mm. For the compact digital DX, this will be 30mm. You can find your camera’s “normal” in the pages of its manual or you can find it on the web.

OK you found out the “normal” for your camera. Let’s pretend its 30mm. Also let’s pretend your subject for today is a robin red breast. The bird is 200 feet distance. You take a picture with the zoom set to 30mm. The image of the bird is too small, you are disappointed. You re-take with a 60mm zoom setting. The image of the bird is now 2X larger, the bird has imaged as if it were 100 feet distant. Again you reset the zoom to 120mm and shoot. This time the image of the bird reveals some details of its uniform. This image discloses the bird as if it were only 50 feet away.

The message is, the focal length and the distance to the subject are entwined and proportional. Mount a 240mm lens and a subject actually 200 feet away, images as it were just 25 feet away.

Macro Lens --- We all like to do close-up photography, you know, bugs and postage stamps etc. If you do this deed, you will find it rewarding as well as challenging. It was especially challenging years ago as most cameras limited close focusing to about 2 feet. This is because the typical camera lens is optimized to image distant subjects and challenged when tasked to image close. This is not just an issue of tack-sharp; this is an issue of under-exposure. You see, the f-numbers engraved on the lens barrel began to go amiss at close distances. This will likely cause under-exposure. To mitigate, camera makers stop the ability to close focus when the error reaches 1/3 f-stop. This happens at about 2 feet.

Photographers are not satisfied; they deploy all manor and means to get closer. As they do, they boldly face under-exposure. Macro lens to the rescue: A macro is optimized for close focusing and slightly compromised when tasked to image distant. The true macro will allow close focus and cleverly maintain the validity of the f-numbers regardless of subject distance.

  • Thank you, Alan Marcus. I think I'm getting there now. I particularly liked your phrase 'the image of the bird reveals some details of its uniform." I'm trying to work out whether it is worth getting a telephoto lens or monocular to clip onto my mobile phone as I'm loath to buy a camera when my phone is always on hand. That's perhaps why I'm seeing x12 and x18, rather than mm. – Sarah Apr 16 '18 at 12:59
  • @ Sarah -- Phone cameras are nifty but they can’t hold a candle to a modern digital. As you know, phone cameras have their limitations especially when it comes to the realm of telephoto. You care thinking about mounting a supplemental lens. These mate up with your phone camera adding wide-angle or telephoto. The problem is: These supplemental lenses come with their own baggage. My advice – buy a high-end point and shoot digital camera. They are nifty plus they now have super zoom lenses and they fit in your pocket or purse. – Alan Marcus Apr 16 '18 at 13:10
  • @Sarah If you could edit into the main question that it is add on lenses for phones you are looking at that might be helpfull. – lijat Apr 16 '18 at 15:31
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Personally I am playing with a Nikon P900 that has 24mm-2000mm optical zoom.

A 24mm zoom is wide angle, good for capturing more objects in your immediate vicinity, like capturing more area of a small room, a much wider field of view.

A 2000mm zoom is 40 times the magnification of a "normal" 50mm lens, taking in a very narrow field of view. Is great for getting ultra close to nearby objects like birds in the 15-100 foot range. At 2000mm it is also good for objects at distances like 300 feet provided you either have a very steady hand or a tripod. When you are using extreme zooms like 2000mm, remember that the further away an object is, the more that camera shake will fuzz the image, so play with tripod and play with shutter speed to reduce shake.

My P900 will go to 8000mm digital zoom (getting fuzzier and fuzzier) or 160 times magnification of a normal 50mm lens. Mounted on a strong tripod and using fast shutter speed I have obtained somewhat fuzzy but nevertheless recognizable closeups of adult deer at 1000 feet, so the deer nearly fills the frame.

(BTW there are lots of weak tripods out there. I have one very strong tripod, an ancient STAR tripod that extends to 6'6" and weighs 12 pounds. I have a much lighter tripod that weighs about 3.3 pounds, a Zomei Z888C that cost me $159 15 months ago, and performs reasonably well, though is not as solid as the STAR at extreme ranges.)

  • I would not recommend using a digital zoom... and you are not answering the question – Olivier Apr 16 '18 at 21:06
  • I recommend not using the term zoom when referring to specific focal lengths. For instance, "A 2000mm zoom is 40 times..." is better said as "A focal length of 2000mm is 40 times...", etc. – scottbb Apr 17 '18 at 0:02
  • That's really helpful. Caleb, I see now a simple distinction between telephoto and zoom. Thank you. As you'll see from my edited title, I'm actually thinking of getting either a clip on lens or a monocular for my mobile (Galaxy S7). The question about clarity is really that I am forever photographing birds, squirrels etc and usually at some distance. My mobile does a great job at medium distance but zooming in just leaves me with a fuzzy blob where a bird should be. – Sarah Apr 17 '18 at 6:20

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