Mr PC Loc: Austin, TX

I've read a few online articles and I understand a bit about different sized sensors giving you a different effective focal length than what's imprinted on the lens body. My question is, what is 1x zoom? Is it 35mm and everything else is a multiple of that? I read somewhere that a 55mm lens pretty much duplicates what the human eye sees in terms of magnification. With super zoom p&s cameras going out to nearly 50x zoom, it made me curious how that compares to say, my 55-300 Nikkor on a APS-C sensor. As the famous scientist Barbie once stated so eloquently "Math is hard!" So please try for a plain English explanation. Thanks, gang!

dooragdragon Loc: Alma , Arkansas

Mr PC Loc: Austin, TX

Thanks, Pete, that cleared it up pretty nicely. And it wasn't post-graduate calculus.

f8lee Loc: New Mexico

If I am understanding your question, the "X factor" of a zoom lens (any zoom lens, for still or video use) is simply the ratio of the longest-to-shortest focal length. So a 50-200MM zoom is a 4X, a 10-20 zoom is 2X and a 25-300 zoom is 12X.

Now the chip size impacts the field of view that a give focal length affords. With a larger imaging chip (or piece of film) a given focal length gives a wider angle field of view. You can understand this intuitively with a pencil and paper:

On a blank sheet of paper, draw a horizontal line, say, 1 inch wide, across the bottom middle of the sheet. This is the "sensor".
Next, draw a dot about 3 or 4o inches above that line and centered over it. This is where the light going through lens "crisscrosses".
Then draw a pair of lines from that dot to both ends of the line. That represent a certain angle, right?
Now (and here's the aha part) draw a longer line (say, 4 inches wide) just under or over that 1" line from before. Draw a pair of lines from that same dot (the "focal length") to the ends of that longer line and voice - you see a wider angle of view.

The reason manufacturers in the still world "translate" focal lengths to their equivalents (based on angle of view, actually) to the MM numbers we're all familiar with is because those were the lengths used in the wildly popular 35MM film format in the old days. A "normal" lens in 35MM shooting was about 50MM focal length, but for Hasselblad or other 120 film users the normal lens was really 80MM, and for 4x5 sheet film users the normal lens is 150-160MM.

Hope that helps, Barbie.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

A 50 mm is said to be normal because the angle of coverage is about the same as normal vision. Although yoy may have a 20 to 1 zoom say 50 to 1000 the magnification will not be 20 times bigger. In fact if you double 50 about 4 and 1/ 2 that will be the magnification. In other words an image will appear to be 4 1/2 times bigger at the long end of the zoom.

amehta Loc: Boston

When you put your 55-300mm lens on a DX camera, people talk about the 1.5x crop factor and refer to it as "magnification". There is no optical magnification happening. The magnification happens when you display a full-resolution image. If you take a picture with your lens on an FX camera and a DX camera, and put both pictures on your computer monitor using full screen, the DX image will be magnified, showing a smaller portion of the scene (smaller field of view), but showing things larger.

f8lee Loc: New Mexico

This is correct only for full frame digital cameras, as they mimic the 24x36MM dimension of 35MM film. As I already pointed out, "normal" lens length varies depending on the size of the imaging chip (or film). To the tiny chip in your cell phone, a "normal" focal length would probably be about 4MM. For Ansel Adams and his 8x10 inch view camera, a "normal" lens would be a 300MM focal length.

This is a commonly misunderstood concept - all because the manufacturers wanted to make it easier for most people to understand the basic view a given lens will give on their camera. The micro-4/4 format has a 2X crop gator, meaning that a 100MM lens on that camera will give about the same angle of view as a 200MM lens would on 35MM film (or FX digital)

Mr PC Loc: Austin, TX

Thanks everybody! No mathematicians were harmed in the answering of my seemingly simple question.

mapster Loc: Wisconsin

I have never understood the FX/DX thing very well, this is a great explanation for me! Am rather new to DSLRs and photography in general. So, if I use a fX on my. d 3200, I just don't get the full advantage of the f X lens?
Thanks!

jgitomer Loc: Skippack Pennsylvania

You get more than the full advantage! :D

Because a DX camera sensor is physically smaller than the sensor on an FX camera the corners of the image on the sensor are closer to the middle of the sensor.

Since lenses tend to be sharper towards the middle than in the corners with most lenses this means you will actually get a sharper image than when using a comparable quality DX lens.

Jerry

jimmya Loc: Phoenix

I love the "barbie" reference... cute.

amehta Loc: Boston

There are two sides to the FX lens on DX body question, wide and tele, with the middle being about 35mm. This isn't completely random, it's based on the size of the sensor, which diagonally is about 28mm.

For focal lengths wider than this, an FX lens will be much more expensive than a DX lens, because it has to cover a much bigger sensor (43mm instead of 28mm). You are essentially throwing away all that effort, after paying a premium for it. So an "ultra-wide" zoom lens or DX would be something like the Nikon 10-24mm f/3.5-4.5 which costs about $800. The closest FX lens is the enormous Nikon 14-24mm f/2.8 which cost $2000. They just can't make an FX zoom starting at 10mm, that's fish-eye territory.

For focal lengths longer than the middle range, DX lenses can be smaller, but FX lenses will work fine. Nikon makes the 55-200mm and 55-300mm zooms which are kept fairly small, and they make an 85mm macro lens. And that's it for lenses which start past 40mm. Basically, they're saying to DX camera users, "if you want telephoto, get an FX lens". And, as Jerry suggested, that's not the worst thing for you to do. You pay a little more (the 70-300mm does cost more than the 55-200mm), and it's a little bigger (ok, a lot bigger, 12oz vs 26oz), but you'll get excellent image quality.

mapster Loc: Wisconsin

Okay, I am slowly getting this. So my next question is, I currently have an18-55kit lens. I also purchased the 55-300 lens when I purchased the camera around this time last year the Nikon D3200. I also own the 105 macro- which I love! I am looking for a good walk around lens , to take on a trip around USA this fall, what would you recommend? I have a monopod I can take and we would probably do some hiking, so I only want one lens to do "close" as well as far. I am not TOO concerned about price, but would like to stay around $1200.00 or so. Would-also probably like to move up to DX in the future.....from the sound of things
Thanks for the help!
:-D

amehta Loc: Boston

I'm going to let others answer this question, since my approach is the exact opposite. :-) But I think you'll end up with a "superzoom", either the 18-140mm ($600) or the 18-300mm ($1000).

You might want to make a new topic for this question.

mapster Loc: Wisconsin

Thanks for the input, if I make a new topic, do I have to start all over? Have never started a topic much less taken it from this point?!