How does focal length relate to macro magnification? [duplicate]

Question

I'm new to photography and would like to know a little more about zoom lens, The main thing I wonder about is this, I have a Fujifilm S4000 camera that claims to have 30x magnification.

The new camera I now own is a Nikon D60 with it's kit lenses (18-55) I was willing to get better lens to get a larger zoom range, and eventually reached 70-300mm lens made by Tamron ( Tamron AF70-300mm F/4-5.6 Di LD )

Now those lenses have a quite large range compared to what I have on my D60 right now, but when calculating the magnification ( 4.2x ) it's not even close to what the Fujifilm is offering.

So obviously I am missing something, or am I? Will I get more magnification with my D60 together with the 70-300 lens than the Fujifilm? Does the sensor size play a role here when it comes to that? and what else should I take into consideration when trying to compare the magnification between my cameras?

About the focus, what I was wondering about is the fact that some lens with big ranges like the 70-300 I stated above, claim to be "Macro" lenses, does that mean that they somehow have more focus range so that even if I zoom quite far I will be able to focus? I guess the question could be what would make zoom lens "Macro" lens?

Any info that would help me learn more would be much appreciated.

Answer 1

The whole point of DSLR cameras such as your Nikon D60 is that they are interchangeable lens cameras. This allows the use of specialized lenses that are designed to do a specific task extremely well, rather than restricting them to a single, jack-of-all-trades lens such as is permanently attached to your Fuji S4000.

If the most important criteria to you is zoom range and maximum magnification with a single lens, you were better off with the Fuji, even if you spend a boatload of money on a wide variety of lenses. Look at it this way: You can buy a Nikon 16-85mm f/3.5-5.6 DX lens, and a Nikon 70-300mm f/4-5.6 VR lens and take most of the same pictures you could with the Fuji. The image quality would be better, but you still wouldn't be leveraging the potential of your Nikon 60D. If you really want the reach of the Fuji, you need a 500mm Nikon lens, and 500mm from anybody isn't cheap. But any 500mm lens currently on the market (other than a cheap, fixed aperture, low quality mirror lens) is going to allow you to shoot at faster shutter speeds and your images will have significantly less noise (due to the greater light gathering capability of the much larger sensor) and more control of the depth of field than you could do with your Fuji.

If you really want to harness the power of your D60, you need to learn why prime lenses account for the vast majority of the worlds best photos in terms of technical quality. Prime lenses have only a single focal length and no 'zoom', but they often have much wider apertures that allow you to shot at f/2, f/1.4, or even f/1.2! That is close to 5 stops difference! All other things being equal, a picture you would need to take @ 1/15 sec at longer focal lengths on your Fuji, which would leave any moving subjects blurry, could instead be taken at 1/500 sec which will freeze all but the fastest athletes! Sure, you can capture an historical moment with inferior equipment and win a Pulitzer for the way you communicated the moment. But in terms of pure image quality, the old saying "Gear doesn't matter" is only half true. The truth is, "Gear doesn't matter, until it does." If you need your camera to perform beyond its technical limits to pull off a shot, at that point the gear does matter because it is preventing you from getting the shot you want.

In purely technical terms, your Fuji S4000 has the equivalent zoom range of a 24-720mm lens on a FF camera. For your 1.5X crop body D60, that translates to a range from 16-480mm. What you lose with the Fuji is light. A LOT if it. The sensor on the Fuji measure 6.17mm x 4.55mm. That gives it roughly 1/14 the area of the 24mm x 16mm sensor in your D60. Even though the Fuji has a 14MP resolution, compared to the D60's 10MP, those pixels are so tiny they don't collect near as much light as each of the much larger pixels of the D60 can. This results in lower image quality, especially in lower light environments.

As for the relationship between Telephoto zoom and Macro capability, there really isn't one. Macro lenses allow closer focusing than most lenses. By allowing you to get the subject closer to the camera, it allows you to increase the size of the subject in your photo. Macro capability is measured in terms of Maximum Magnification (MM) that is only indirectly related to focal length. Magnification is expressed as the ratio between the actual size of the subject and the size of the subjects image that is projected onto the film/sensor. A 1:1 Macro lens, which has an MM of 1.0x or 100%, means if the subject is 15mm tall, the lens can get close enough to project a properly focused image of the subject on the focal plane that is 15mm tall. A 1:2 lens would have an MM of 0.5x or 50% and would project an image 7.5mm tall of the 15mm subject. This is because if both lenses are the same focal length the 1:2 lens would require twice the distance to properly focus on the 15mm subject.

Most high powered telephoto lenses are designed to focus on very distant subjects, not to reproduce nearer subjects at high magnifications. A 600mm lens will do very well at taking a 6 foot tall human at very large distance (a little over 400 feet) and filling the 36mm tall sensor frame (full frame is 36mm x 24mm) in portrait orientation. I've never seen a 600mm lens that can get close enough to a 36mm subject to fill the same frame and properly focus on it. By the time you are close enough to the subject, you are inside the lens' Minimum Focus Distance (MFD) by several yards/meters. Most very long telephoto lenses have very large MFD and thus small MM numbers. That is what a Macro lens is designed to do: by reducing the MFD you can focus on a much closer object and get a higher MM.

There are some telephoto zoom lenses on the market, usually in the 70-300mm range, that claim to be Macro capable. But if you examine the specifications of such lenses, you see that at best they are 1:3 in terms of magnification. They can only focus close enough to project a 15mm image of a 45mm subject. That gives them an MM of .33x or 33%. While it is theoretically possible to design a zoom lens with 1:1 Macro capability, it is not practical. Most true Macro lenses have a fixed focal length designation that allows them to be simpler, cheaper than a comparable zoom lens would be, and produce better image quality at closer subject distances.

Answer 2

x numbers on zooms are a bit deceptive. If you have a lens that is 1mm to 30mm, it's a 30x zoom, but it won't have nearly the reach of a 70 - 105mm lens, even though that lens is less than 2x. You would do well to completely forget any x multiplier numbers you have ever dealt with as they are a useless number, what matters is focal length range, the longer the focal length, the more magnified it will seem and the further out you can shoot an image.

Typically point and shoots can pull off ridiculous multipliers because they have a very small sensor with very cheap optics, this means that they can easily make a lens that has something like 2mm to 60mm and slap a 30x label on it even though the lens isn't that great.

The other thing that comes in to play here is crop factor though, since a point and shoot has a very small sensor, it takes crams all the pixels in to a very small space, so a picture taken from a 2mm lens on a point and shoot will look similar to a picture taken on a much longer focal length on a DSLR with a larger sensor. This is what the crop factor captures (because it is the amount of cropping that occurs from a typical 35mm film camera). Say for example that your point and shoot had a crop factor of 4 and your DSLR had a crop factor of 1.5 (most Nikon crop sensors) (typically that or 1.6 (APS-C) for most non-full frame DSLRs). This would mean that the 2mm focal length on the point and shoot would be like an 8mm lens on a full frame camera or 5mm lens on an APS-C camera.

The thing is that with the small lens, they take shortcuts so that the image circle (the image that the lens projects on the sensor) is only as big as it needs to be to cover the part where the sensor is. This is what allows the lens to be so much smaller and cheaper. When you move up to an APS-C, or even bigger, full frame, you can't take those shortcuts anymore. That is also why there are some Nikon lenses that are much cheaper but will mention they aren't compatible with the full frame lines.

You are also missing the fact that zoom range always comes as a trade off to image quality. It is hard to make a zoom lens, the wider the range, the harder it becomes and the more optical tradeoffs have to be made. You can overcome some of them through size and cost, but it gets exorbitant pretty fast and can only go so far. This is why in Canon's lens line up for example, the 24-70 f/2.8 lens is $2400 but you can get a $200 50mm lens that will produce just as good of images at 50mm.

This means that while you can buy a lens with something like a 22-300mm focal range, it isn't really ideal since it has to make so many tradeoffs for that range. You are much better off in most cases to go for multiple lenses at shorter focal length ranges that will give you better image quality and then swap lenses when needed. This and sensor size are two of the main advantages of shooting with a system camera such as a DSLR.

As for the Macro lens bit, it is mostly the minimum focus distance. Lenses can only focus so close and a macro lens allows focusing much more closely so that you can zoom in on something small rather than something far away.