Confused by DSLR lens terminology

[FloridaGal]

Hi everyone,

I am very confused by lens terminology and would really appreciate it if someone could give me the "lenses for dummies" answer to my question.

I presently have an Olympus SP 500UZ; a 6 megapixel point & shoot with a 10x zoom which the documentation says is equivalent to 38 mm to 380 mm. On the lens itself it says AF zoom 6.3 - 63mm 1:28-37. So I really don't know what that means, but it has never mattered ... I just know that when I use the zoom button, things get closer, but cropped.

But now I am thinking about a camera that would take better pictures with more zoom and so I am looking at the entry level DSLR's ... specifically the Olympus E-510 (10 megapixel) ... but when I look at lenses I realize that I do actually need to understand this "mm" thing.

There is a 2 lens kit for the E-510 that includes a 14-42mm f3.5-5.6 and a 40-150mm F4.0-5.6 ... but I don't really know what this means. I take a lot of pictures of birds and sometimes the pesky little fellows don't let me get too close ... hence my desire for a sharper picture taken from a greater distance. Is there any easy way to calculate how much zoom I get at a certain distance? i.e. will a certain lens number give me a zoomed in shot of a bird that is 25 ft away? 50ft? 100 ft?

Also, if anyone knows of websites or books that really "dumb down" the terminology I'd appreciate it.

Thanks!

[Codebreaker]

Beth....

Expressing lens characteristics in 'mm' is defining the the Focal Length of the lens. What's that I hear you say?

Well rather than get technical I'll answer the second question which will explain about Focal Length. In a nut shell the longer the Focal Length the close the subject will appear. So a 200mm lens will get you closer than a 50mm lens.

Focal Length is a physical characteristic of the lens, so for DSLR lenses no matter what camera you put them on the Focal Length is always the same.

However, confusion now creeps in because most Digital Cameras can have sensors that are physically smaller than 'olde' 35mm film. This means that if you put the same lens on a 35mm film camera and a typical digital camera, the digital camera 'appears' to have zoomed in because you're seeing less of the scene. It's like having an image and cropping something out of the middle. Which is why digital camera sensors are often called Crop Sensors.

So your 6.3 to 63mm is equivalent to a 35mm camera using a lens of 38 to 380mm.


Hope this helps.

Colin

[msbrad]

Thank you Colin,
Your answer helped me.
m

[FloridaGal]

Thank you! Do I get a follow-up question?

Since the E-510 kit lens of 40-150mm is the 35mm equivalent of a 300mm 35mm, and my present point & shoot is a 380mm equivalent, doesn't that mean that I will end up needing to be closer to the subject with the new camera than I presently do with my old camera? And so the solution to that would be a "zoomier" lens? Like the ED 70-300mm f/4.0-5.6 which is the 140-600mm 35mm equivalent? And is there a formula that says if the distance from your subject is X, and your subject size is y, then to get a decent shot your mm# should be z?

Thanks again!
Bye,

[Codebreaker]

Hi Beth....

If the 510 equivalent is 300mm and your P&S equivalent is 380mm then you'll need to stand closer.

As for a formula I don't think it's that simple because the missing factor is how much do you want to fill the frame. Maybe some one else can shed some light on this.

As an example though I used a 300mm on my Canon which gave an equivalence of 480mm. A Goldfinch only appeared about 2/3rd of the height of the frame (in Landscape mode) when taken at a distance of about 4m.

Colin

[Chuck S.]

Colin, the factor for adjusting lens focal length from film SLR to digital SLR is confusing. It gives the impression that somehow that lens magnifies more when attached to a DSLR; as you know, it doesn't. A 300 mm lens mounted on either camera projects an image to the film or sensor that's exactly the same magnification; a 300 mm lens is approximately a 6-power magnifier. However, in the case of the film SLR, you have a relatively large surface onto which the image is projected, so more of that 6 power image is caught on the film. However, the smaller sensor on a DSLR only captures the heart of the image, leaving out a bunch of stuff that was captured on the film. In effect, the DLSR is cropping the image in-camera.

However, if I then develop the images from the film and digital, then print 4-by-6's, the DSLR image appears to be at a higher magnification. In reality, the DSLR image is a crop of the film image that has been upsized.

Again, probably not worth a whole lot of discussion, but I just keep telling myself that my long lenses didn't truly get longer just because they're now attached to a DSLR!

[Codebreaker]

Hi Chuck....

That's really what I was saying - just using different words

Colin

[Chuck S.]

Originally Posted by Codebreaker

Hi Chuck....

That's really what I was saying - just using different words

Colin

And fewer words - which is a good thing!

[Big AL]

I'm not familiar with the Olympus lenses...I use Canon, but as far as how you would use the lenses you mentioned....The 14-42mm would be for close up shots like maybe a car show or of flowers and normal family shots. It would probably be a good wide angle shot for scenery. If it has macro settings thats what you would use to get really close like for bugs or close up flower shots. The 40-150mm is a good everyday range or for if you are on a hike....enough for a close animal but with enough zoom for that bird 50 feet away. It also would work well for portraits and family shots. If you are specifically into birding, you will need probably a minimum 300mm. I use a 70mm-300mm lens which works well, but I would really like a 500mm. Of coarse the bigger and better the lens means the more cost. Since my wife laughed when I gave her my Xmas list I guess I will be waiting a little longer for that lens

[GaryK]

Hi Beth

Without getting into it too much, there is a bit more to lenses than just the mm comparisons. You are correct though, that the bigger the number the zoomier it is.
If you are new to DSLR terminology as well as technology, ask questions before spending the money. Loads of people here will be willing to help without the egos and brand bashing you find on some photography sites.

It is not hard to pick up the slang and pretty soon you will be throwing jargon around like a pro.