Techy numbers and mm of lenses..Dummys Guide to...

BengaLover

So, I am totally clueless about lenses and the finer details of what to buy, but I have just had to put up for sale my lovely lenses that i dropped for a someone else to buy to repair, they are 28-80mm.
They are a macro lens and I want to buy the same ones again and have found some on ebay, but if I wanted a macro lens for even closer macro, what mm would I need to buy, and should I look for anything in particular? Thanks.

5uspect

Just because it says macro on the lens doesn't mean it a proper macro lens. It might just focus a bit closer.

A true macro lens is capable of 1:1 reproduction. That means that if you're taking a picture of a bug an inch long then the image of the bug projected onto your sensor is also an inch long. In order to achieve this reproduction ratio without the front of your lens casting a shadow over your subject macro lenses tend to be more in the telephoto range.

So while your wide angle lens will let you get close a 100mm macro is going to be superior. An alternative route to go down is using extension tubes or a bellows with a 50mm prime. These add space between the camera and lens and let you get super close.

BengaLover

Yeepers..Thesewere the lens I droppped (hope its ok to post the link here to show them)
http://www.adverts.ie/lenses/fantastic-sony-sigma-lens-macro-28-80mm-aspherical-for-repair-a-mount/1663403

I want the same specs or better, these are 1:3.5, so if I were to get better, I would be looking at a lower ratio there is that right?

5uspect

That lens has a minimum f-number of f/3.5. That's a measure of how big the aperture can get. It's not the reproduction ratio.

BengaLover

I wonder if its worth getting in touch with the guy here who has a repair service..?
5uspect, thats a great link to explain things to me, thanks..I have total cotton wool brain when it comes to anything with numbers.

Heebie

The numbers on a lens are generally:

The (effective) focal-length. generally denoted by a number and "mm" and on a zoom lens by a set of numbers followed by "mm"

This is the distance from the "focal point" of the lens (thinking of this as the center point between the front-most and rear-most element of a lens is easier than trying to explain what it actually means.) to the imaging plane (film, or image sensor etc..)

The longer the focal-length, the more magnification the lens is providing. I said effective above, but some trickery can be done with mirrors etc.. to give you the effect of a longer focal-length without actually having a lens that long. (a 1,000mm lens that's nowhere near 1000 mm long, for example, will have a mirror behind the front-most lens, and another mirror in front of the rear-most lens, and the light will come in the front of the lens, bounce of the mirror in the back, then bounce off the mirror in the front, and travel all the way back through to the image sensor/film, so the focal-length of the lens can be approximate 1/2 of 3 times the physical length of the lens.

Good explanation here:
http://www.paragon-press.com/lens/lenchart.htm

The F-Stop is a measure of how much light the aperture lets into the lens. You can consider it the "speed" of the lens. The scale of it is based on a stop of exposure, which is a particular amount of light during a particular amount of time.
The more light is allowed into the lens, the "faster" a piece of film or an image sensors will gather all the light that it needs for a "correct" exposure.

Letting in a lot of light will expose your image quickly, but it causes the depth-of-field to be shallow.

The depth-of-field is the size of the plane of space that is "in focus". If you photograph a long ruler or tape measure that is setup to be in a line moving toward or away from your lens, with a shallow depth of field, you'll get a small space in-focus. (using the focus control on the camera will cause that small piece that is in-focus to "move" either towards, or away from, the lens)
If you increase the F-Stop to let less light into the camera, the depth-of-field gets larger, so you get a larger piece of the tape measure in focus.
If you increase the F-Stop enough, you eventually get to a point where (effectively) everything is within the depth of field, so everything is in focus.
The faster the lens, the shallower your depth-of-field can be. (at f1.4 you should get a very shallow depth of field. If you go to f2.8, you should have around twice as much depth.. at 1.4 you should easily be able to take a photo where the tip of a person's nose is in-focus, but their cheeks and eyes are not. going to say f4, you'll probably get a fair bit of their face in focus without changing the focus of the lens.

More technical explanation here: http://www.uscoles.com/fstop.htm

Hopefully that was helpful.

BengaLover

Very helpful thanks.
What Im aiming for is not to get bogged down with too many lenses, so I have the standard 18-55 that came with the camera just for 'snaps', and one for taking long distance pics, and then one for jolly good macros.
Dont suppose there is one good lens that would do all three things?

Heebie

Depends on how close you want to get to your subject.
I have a Sigma 17-70mm for general stuff, a Tamron 70-300mm with macro mode for zoomy & macro-y stuff, and then some other more specialised lenses... quite a few of them.
Generally if I'm trying to travel light, I'll carry those two, my 10-17mm fisheye and my 10-20mm aspherical wide-angle, and my 30mm f1.4. That all fits in my sling style bag, along with my battery-grip or a flash.

BengaLover wrote: »

Very helpful thanks.
What Im aiming for is not to get bogged down with too many lenses, so I have the standard 18-55 that came with the camera just for 'snaps', and one for taking long distance pics, and then one for jolly good macros.
Dont suppose there is one good lens that would do all three things?

DaireQuinlan

Heebie wrote: »

I have a Sigma 17-70mm ... a Tamron 70-300mm ...
Generally if I'm trying to travel light, I'll carry those two, my 10-17mm fisheye and my 10-20mm aspherical wide-angle, and my 30mm f1.4. That all fits in my sling style bag, along with my battery-grip or a flash.

I'm having difficulty equating the phrase 'travelling light' with that list of gear 'travelling light' for me is a camera body w/ one lens. If it starts raining I'll stick it under my coat.

Heebie

Travelling light is 4-5 lenses.. my total kit is closer to 20 including some really fairly esoteric glass, and stuff like my Tamron 70-200 f2.8.. love that lens. It's like a cannon! (not to be confused with a Canon) I also have a travelling lightER bag and a point & shoot.

DaireQuinlan wrote: »

I'm having difficulty equating the phrase 'travelling light' with that list of gear 'travelling light' for me is a camera body w/ one lens. If it starts raining I'll stick it under my coat.

BengaLover

There are so many to choose from I guess for an amateur like myself who is just purely a hobbyist that its best to keep it simple.
Anyhow I just won an auction on ebay and got the same one for 19 dollars so am really happy.

Gregor Samsa

BengaLover wrote: »

if I wanted a macro lens for even closer macro, what mm would I need to buy, and should I look for anything in particular? Thanks.

You've a Sony (A-Mount) camera, right?

The two dedicated macro primes that A-mount users seem to prefer are the Sony DT 100mm F2.8 Macro lens or the Tamron AF 90mm Di f 2.8 Macro. Sigma also have two Sigma 105 F2.8 EX DG macro lenses (one with a HSM auto-focus motor, and a cheaper one without), but I don't know too much about them. However, I wouldn't be too concerned with an auto-focus motor on a macro lens - you're usually better off using manual focus for macro anyway. If you have one of the Sony SLT cameras, the Focus Peaking feature is a godsend.

Personally, I have the Sony 100mm f2.8 macro. I also have a Sony 50mm f2.8 macro, which is cheaper and smaller, but 50mm isn't a particularly good focal length for macro - you need to get too close to your subject for 1:1 magnification, which isn't ideal in many situations (it usually scares insects away, or you end up blocking you own light, for instance).

You say in another post that you don't want to get bogged down in too many lenses. As 5uspect said, another option is Extension Tubes. The best option is these Kenko ones : http://www.connscameras.ie/kenko-auto-extension-tube-set/p-4961607900000pd.html. You'll be able to use them with any lens, either individually or in any combination to obtain various magnifications, with no loss of sharpness (but you do lose some light). If you then later decide to get a dedicated macro lens, you can still use them to get even better magnifications than 1:1.

And well done on getting that lens for $19. Some bargain!

Gregor Samsa

BengaLover wrote: »

Very helpful thanks.
What Im aiming for is not to get bogged down with too many lenses, so I have the standard 18-55 that came with the camera just for 'snaps', and one for taking long distance pics, and then one for jolly good macros.
Dont suppose there is one good lens that would do all three things?

One lens won't ever do everything (this is why there are so many lenses). But if you want a good all-round lens, the Tamron 18-270 PZD is hard to beat. Like any superzoom, it's a compromise, and it won't do true macro. But it is sharper than your current 18-55. The PZD motor means that auto-focus is fast and pretty much silent (great for video).

It's the default lens I carry on my A77, and I absolutely love it. I have lots of lenses - a wide angle, various primes and a top quality 70-400G that cost far, far too much, but if all my gear got stolen or destroyed, this would be the first lens I'd replace.

DaireQuinlan

Alternatively find what the well regarded primes are for your system and get a semi wideangle and a short telephoto and just go with that. It'll probably end up cheaper or roughly the same cost as some crummy off-brand superzoom, and I gaurantee your photography will improve as a result if you become accustomed to thinking just in terms of one or two focal lengths.