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Category: New Questions

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Photography Question 
COLM CASSERLY

member since: 4/18/2005
 

Just What Does Macro Mean?


Hi, I recently bought a Nikon 35-70mm lens (manual focus) on eBay. It's described as f3.5-4.8 and has a macro facility. Since I have no manual book, I wonder if anyone could clarify for me - what's the macro facility mean? I was expecting a button or switch, which would allow it to zoom more or focus better?? Also, what does the aperture range mean? My other lens is a 200mm f2.8, so that's easy to understand. But I don't know what it means to have a range like 3.5-4.8. Does this mean at certain focusing ranges I can't go lower than 4.8?? I'm only a beginner - thanks a million.

6/7/2005 7:24:08 PM

 
Andrew Laverghetta
BetterPhoto Member

member since: 9/13/2004
  Macro means getting the frame filled more with the subject. For example, 1:1 (one to one, a ratio) would allow you to take a picture of a penny and set it on the negative so that the penny and the image on the negative would be exactly the same size. This usually costs a lot. Let's see, I'll try to make this more concise. A MACRO-specific lens lets you move the lens closer to the subject and still focus sharply, instead of still being out of focus. Does the lens say "macro 1:(insert something like 1-4) on the front or barrel?
Most lenses that say "macro setting" really mean that they can focus somewhat close. You'll just have to see how close it can get. Anyways, macro means close-up photography. Check out insect or flower photography, for examples.
The 200mm f2.8 has a constant wide aperture. When you have a zoom lens, it's usually more expensive to keep that large aperture at the same size/value all the way from 35mm to 70mm. More basically, at 35mm, you can use f3.5 but at the full 70mm, your largest aperture will be f4.8. Just make sure you're aware, the lower the 'f' number, the larger the aperture. There will probably also be a midway aperture value, possibly f4.0 will be the widest you can go at 50mm? Not sure, though. Hope this helps!

6/7/2005 9:14:29 PM

 
John A. Lind
BetterPhoto Member

member since: 9/27/2001
  Andrew gave a good definition for the magnification ratio often used.

In general, anything that is 1:4 magnification or greater . . . 1/4th life-size or larger . . . on the recording medium (film or CMOS/CCD) is considered a "macro." Magnifications between 1:8 (1/8th life-size) and 1:4 are usually called a "close-up" and not a macro.

Most non-macro lenses will allow focusing to about 1:8 magnification; a focus distance of about 8X the lens focal length (true focal length, not an "equivalent" one). Some will allow closer focusing to about 1:6, and a few (usually telephoto) will only focus to about 1:10 magnification.

-- John Lind

6/14/2005 7:01:33 PM

 
COLM CASSERLY

member since: 4/18/2005
  thks guys, so macro just means ican go in closer on an object. cool. as for the appurature question - you said I can only shoot at 4.8 at 70mm. I didnt realise this. does this mean when I take photos at f3.5 at 70mm (as I have been doing, but yet to develop) that these shots will not come out right. its strange that the lens allows me to select f3.5 at any focal length. how am I supposed to know what focal lengths are acceptable at f3.5?? just guess? thks guys, this is helping. IM ALMOST THERE :)

6/14/2005 7:21:03 PM

 
Andrew Laverghetta
BetterPhoto Member

member since: 9/13/2004
  I think that if you're shooting at f3.5 at the longest lens setting (70mm), then I think that it comes out as if you were shooting it at f4.8. I think on most newer lenses or autofocus lenses, you can set the aperture at (for instance) 3.5 at the widest setting but as I turn the lens words 70mm or the longest focal length, it gradually changes the largest aperture (lowest number like 3.5 or so) to a smaller aperture like 4.0 and 4.8. It's just that it can't keep the aperture as large in relation to the movement of the glass inside the lens.

John might like to give more techincal input about this as he knows much more that I, or be able to correct something.

6/14/2005 8:04:24 PM

 
Matthew Slyfield
BetterPhoto Member

member since: 4/5/2005
  Andrew,

The f-stop changes as you zoom a telephoto lens, but this is not because the actual aperture is changing. F-stop is the ratio of the focal length of the lens to the diameter of the aperture. So if you increase the focal length, then the f-stop changes. At F4, the focal length of the lens is 4 times the diameter of the aperture.

6/14/2005 9:52:45 PM

 
Andrew Laverghetta
BetterPhoto Member

member since: 9/13/2004
  That's what I was dabbing at in one of the last sentences I wrote..."It's just that it can't keep the aperture as large in relation to the movement of the glass inside the lens" but the technical part of it wasn't asked. All you need to know in this situation is that it can't continue the larger aperture at the longer focal lengths. I understand this, so this is why I usually write f/4.0 or such because it is a ratio. Like I said, I didn't feel that it was necessary to going into that kind of detail when you could just say that it wouldn't let as much light in no matter if it still says 3.5 or not.

6/15/2005 2:56:48 PM

 
John A. Lind
BetterPhoto Member

member since: 9/27/2001
  Variable Aperture Zoom Lenses:

Most zoom lenses are variable aperture . . . the aperture changes with focal length. Constant aperture zooms that maintain the same aperture throughout the focal length range are typically the fastest, most expensive and are targeted for the professional market. Allowing the lens to vary its aperture across the focal length range is less expensive to manufacture and allows the lens to be at least somewhat smaller and lighter.

I have one variable aperture zoom lens, a 35-105mm f/3.5~4.5 and will use it as an example to explain a few things about them.

Wide open, at 35mm focal length the aperture is f/3.5 gradually stopping down to f/4.5 at 105mm. Wide open at 35mm, the effective aperture diameter is 10mm. However, wide open at 105mm, the effective aperture diameter is just over 23mm. If the aperture diameter remained at 10mm, it would be f/10.5 at 105mm. It's obvious there's some hocus-pocus going on inside the lens to provide for a larger effective aperture diameter as focal length is increased, but it's not enough to completely compensate and maintain a constant aperture f-number.

Matthew is correct with an important qualification: aperture f-number is the focal length divided by the effective aperture diameter which may or may not be the actual aperture diameter. More precisely, it's the "entrance pupil" diameter formed by the aperture diaphragm as seen from the front of the lens. This is not the actual physical diameter of the aperture hole, but the apparent, or "effective" diameter. The hocus-pocus inside the zoom that varies entrance pupil diameter with focal length is performed by moving the position of the aperture diaphragm. When the entrance pupil equals the diameter of the focusing group (multiple elements of glass inside the lens), it cannot get any larger resulting in an "f drop" and variable aperture. Photographic variable aperture zooms are designed to spread this "f drop" evenly across the entire focal length range. Constant aperture zooms are not just bigger in diameter because they're faster lenses. That's only part of it. The focusing group is more than proportionately larger for the speed increase so that it's larger than the required entrance pupil diameter needed to remain constant aperture. It's why the barrel on them is a large diameter from front objective to just in front of the lens mounting flange.

This caused me to dredge out my 35-105/3.5~4.5, one of my 35-105/2.8 lenses, and my 80-200/2.8 to play with them a bit. In addition to the entrance pupil seen from the front, the aperture diaphragm, as seen from the back is called the "exit pupil." If you have a depth of field preview lever or button on your lens (not the camera body), take the lens off aim the back end toward the (hopefully white) ceiling and look at it from the front at a mid-point f-stop with the preview button depressed. Then change the focal length and watch what happens. It will appear to shrink at the short end and grow at the large end.

Now reverse it and see what happens to the exit pupil. On a constant aperture, I don't believe it will appear to change size (although it will look a different size from what was seen the other way around), but on a variable aperture it will. At least, that's what I observed on mine (and I only have one variable aperture to do this with).

-- John Lind

6/15/2005 9:00:49 PM

 
John A. Lind
BetterPhoto Member

member since: 9/27/2001
  I should add:
Since my variable aperture is an f/3.5~4.5 which is only 2/3 f-stop variation, the change in the exit pupil size wasn't very much at all . . . nowhere near the change in the entrance pupil.

-- John Lind

6/15/2005 9:06:46 PM

 
masih saffarzad

member since: 4/27/2005
  tank yuo for send photo

6/28/2005 4:06:34 AM

 

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