Lens Speak

[LanTec]

I've recently upgraded to one of the new Sony A100 DSLRs and it's the first camera I've had that allows me to change the lenses. What I'd like to know is how to get thru the Lens names to figure out what they do. ie..... 35mm f/1.4G - this one just has one size/length? whereas I have another that's 75-300mm f/4.5-5.6.... whats it all mean and how do you relate that info to what the lens is for? TIA

[Ads]

[ksmattfish]

35mm and 70-300mm is the focal length.

The f/# is the largest aperture the lens is capable of.

The 35mm lens aperture opens to f/1.4. This means there is a hole in the lens 25mm wide (35 divided by 1.4).

The zoom lens aperture is listed as 4.5 to 5.6 because it's f/4.5 with the aperture wide open at 70mm, but when you zoom out to 300mm it's f/5.6 with the aperture wide open.

[LanTec]

Thanks. That helps.
I'm looking for a macro lens and I've been told (unreliabally) that they can go as much a 1:4 how would that be labeled. The ones I've checked all mention 1:1.

[Iron Flatline]

Milimeters:

The mm on a lens are related to the width of the angle they cover. The wider a lens, the smaller a number. Think of a lens that is wide enough to photograph an entire room when you put it in the corner - that is really wide. That migth be a 22mm lens. A very narrow lens tends to also bring things closer, but it' covering a very small area of what uo can actually see with you eye. So if you're really going to get a huge telephoto effect, then it would be a 200mm lens, or even bigger. Pro sports photographers sitting on the sidelines of a football game use a 300mm lens to capture the Receiver's face when the ball got intercepted. If they want to get the whole stadium in one shot, they'd use something a lot wider, such as a 24mm lens.

F-stops:

The aperture is the hole through which light comes into the camera and on to the sensor or film. Aperture openings are called f-stops. The smaller the number (f1, or f2.8 ) the bigger the hole. The bigger the number (f16 or f22 for instance) the smaller the hole. This is some really arcane stuff, but it's how everyone has agreed to label these things, and you will get used to them really fast.

1:1 is very "fast" - that means it can open its aperture very wide, in this case as wide as the lens is long. If it is a 60mm lens, it can also create an opening through which it lets light that is 60mm wide. The wider the hole, the more light gets through - which subsequently means that the faster the shutter can close again.

Whereas a camera might need 1/60th of a second to capture an image at f8 (a relatively medium-sized opening) it might only need 1/250th of a second to capture the same image if the aperture is is f2.8. It will take the same amount of light to properly expose the image.

Metaphor: think of filling a tub with water: you can do a whole lot of water quickly with a fire hose, or you can do it more slowly with a garden hose. Either way you'll need 60 gallons to fill the tub, you can do it quickly or slowly.

[ksmattfish]

When describing macro lenses 1:1 or 1:4 is the magnification. 1:1 means that when you photograph something, it would be actual size on the film/sensor. 1:4 means your subject would be 1/4th actual size. Many lenses are called macro if they can magnify 1:4 or better, but IMHO, a real macro lens does 1:1.

[itsme123]

When describing macro lenses 1:1 or 1:4 is the magnification. 1:1 means that when you photograph something, it would be actual size on the film/sensor. 1:4 means your subject would be 1/4th actual size. Many lenses are called macro if they can magnify 1:4 or better, but IMHO, a real macro lens does 1:1.

So a lense does not really have to be labeled "Macro" to be Macro? I am shopping for a Macro lense too and its a bit confusing with all the different names/descriptions out there .

[ksmattfish]

So a lense does not really have to be labeled "Macro" to be Macro?

I was taught that a "macro" lens can do a magnification ratio of 1:1. There are $500+ macro lenses (prime lenses, not zooms) that can do 1:1, and numerous cheaper lenses (mainly zooms) labeled as having macro ability that can't get close to 1:1. There are some more affordable prime lenses that do 1:2, and can do 1:1 with a screw-on close-up filter, and they may work wonderfully for you. I'm just saying I consider a macro lens to be able to achieve 1:1 without other accessories, and lens manufacturers consider a macro lens anything that can do close to 1:4. To them it's a way to increase sales (adding on another feature), which I think is deceptive.

[itsme123]

I was taught that a "macro" lens can do a magnification ratio of 1:1. There are $500+ macro lenses (prime lenses, not zooms) that can do 1:1, and numerous cheaper lenses (mainly zooms) labeled as having macro ability that can't get close to 1:1. There are some more affordable prime lenses that do 1:2, and can do 1:1 with a screw-on close-up filter, and they may work wonderfully for you. I'm just saying I consider a macro lens to be able to achieve 1:1 without other accessories, and lens manufacturers consider a macro lens anything that can do close to 1:4. To them it's a way to increase sales (adding on another feature), which I think is deceptive.

I see, so if the max magnification of a lens is 1:4 or greater the mfg will not hesitate to label it a "Macro" lens.

Cool, thanks for the explanation .

[ksmattfish]

I see, so if the max magnification of a lens is 1:4 or greater the mfg will not hesitate to label it a "Macro" lens.

I don't know what their criteria is. All I know is that since the mid 1990's a lot of lenses have the word "macro" on the box, and most can't do 1:1.

EDIT: For all the ads and commercials from Canon, Nikon, etc... talking about how important photography is to them, remember that most of it is total BS. They are about making cash money, and will say and do almost anything to get you to spend a buck or two or a hundred. I'm a cynic.

[Mad_Gnome]

35mm f/1.4 G...