After using my 18-55mm and 70-300mm lens for about a year I've decided to try and get an more "all-in-one" lens so I don't have to switch them up so often. I want the ability to shoot wide and to zoom at the same time. So far I've really been considering the Sigma 28-300mm f/3.5-6.3, since it has a good price, good reviews, etc. It's also 300mm, which is great - many lens like this top out at 200mm. I wish it had a lower mm to start (is that called focal point?), like my 18mm, but 28mm will do.

My real question is, beyond the focal point one above, is what do those f/xx-yy numbers really stand for on the lens? I want a real basic answer to this.

I know the higher the numbers the worse my photos will be in the dark and the slower the camera will function in low light. Didn't take me long to figure that out on my f5.8 300mm lens (Nikon 70-300mm f/4.5-5.6G). My 55mm lens is much faster and performs better in low light (Nikon 18-55mm f/3.5-5.6).

But how does the f/stop and aperture of my camera relate to these numbers physically on the lens? I'm a little confused on that.

Thanks

Inside the lens there is a diaphragm (a second shutter if you will) and this close's down when you shoot. It is midway in the lens (take a look when your taking a shot sometime) what that does is increase or decrease the apparent range of focus, so the smaller the number, the less field of focus you will cover, like f2.8 or f3.5.
So a small number equates to a very large aperture, f2.8 being very large, this means more light is let in during the shot- so more light less focus.... A small number like f22 is a very small hole and the smaller the hole the greater the apparent range of focus, but its alot less light, so a tripod may be handy becaue your shutter speed will. So if you were taking shots of a mountain range, well f22 would be appropriate, because you want the farm house at the foot of the mountain to be sharp as well as the snow capped peak.
I cant explain why smaller makes things sharper, and larger is less focus (but it also gives you more light for the shot.)

In a zoom lens, it really won’t matter that much EXCEPT you really want the widest aperture available for the top end (the 300mm end) and like you said its 3.5 to 6.3 that means at 300mm your widest aperture will be 6.3 this cuts the amount of light, and will increase the length of exposure needed. (Making it hard to hand hold low light shots at 300mm)

Thanks Dave, that helps a lot. So basically, keep that tripod with us everywhere next time we use the camera; even if for 'just in case' scenarios.

Yes with the longer focal length (and yes you did have that right, the focal length equates to the XXmm of the lens) and smaller f stop, you will wind up using the tripod much more (or you could get a decent mono pod, easier to use, and carry but require some skill, I still cant use one very well, but I never tried too hard,lol)

An easy way to figure the minimum shutter speed per focal length that will be needed (easy photog trick here, lol) take the focal length of the lens and equate it to a shutter speed, so for 300mm lens, 1/250sec or better for hand held (and really 1/250 is on the light side 1/500 would be a safer bet.)

Thanks. We have a real light tripod we carry on our packs. It's flimsy but we hold onto it really well when shooting shots in "weird" terrain or real windy places (like lava fields, LOL). We took the larger tripod with us as well this year and it worked great, but it weighs so much.

The monopod has also been iffy for me. Natasha has it down alright, but I like my tripod. We probably need to get a better one. If I could find one that was real lightweight, sturdy, and didn't break the bank I'd be set.

Main reason I want this new lens is for heli flights. I HATED having to switch lens in the middle of a flight (especially when the doors are off and the wind is blowing you to death - don't want to loose a lens like that). I also would like it for the convenience of being able to take various focal length shots without having to change my lens, it gets annoying fast. And some of the lens with the Nikon have plastic connectors, so changing them too much makes me nervous.

My main concern with this fstop number (I assume that's what it's called or is that only for aperture?) is taking really dark night shots with NO flash. ie, when I shoot lava (or try to, LOL). I typically end up using the manual settings for this, bc when I let the camera do it, it either overexposes my photo or underexposes it. It was hard getting it just right. This was the best we could do, from the distance we were at this year with the 300mm lens (I think I had the tripod this night, but one night I forgot it and had to use a lava mound [cut myself up too, its like metal glass]). Next year I hope we'll march right up to the flows... it depends on where they are when we are there. 8 miles round trip can be a looong hike in the dark over pahoehoe.

Well that makes things different (knowing what you are using it for) and my best advice would be to find a really good lens that holds the f stop all the way out (it will break the bank, that’s for sure). But if you are planning on doing allot of that kind of photography, well it will be aces.
You are stuck.....hmmm have you ever... oh no film, right digital?
Grrr I was going to suggest some super high speed film. LOL
For Aerial shots, you really need as wide of an aperture as you can afford. (I did a fair amount of the aerial work in my early days, lots of real-estate work)
Think about what you are fighting.. Vibration, darkness..
If you’re not doing a bunch of aerial at night, I say just do the best you can with what you can afford. (or look into renting lenses, that actually may be the best idea)

Luckily no aerial at night, just in the day time. So movement is the biggest issue there, ironically again making my zoom lenses almost unusable.

In the dark they work alright with a tripod on land, but maybe you're right.. we should just spend the money and get a better fstop lens. Not sure we can afford it for the next trip, but maybe down the line for sure.

I have a great tripod, its $120 Cdn but worth every penny. Its a very sturdy tripod but also lightweight and extends very high.

Knight Rider wrote:

I have a great tripod, its $120 Cdn but worth every penny. Its a very sturdy tripod but also lightweight and extends very high.

Can you show me a photo of it online somewhere? Or let me know the brand? I'd like to look it up.

I think someone told me to get a tripod with round legs, not square. Not sure why, maybe it's more sturdy?

kanaloa wrote:

Knight Rider wrote: I have a great tripod, its $120 Cdn but worth every penny. Its a very sturdy tripod but also lightweight and extends very high. Can you show me a photo of it online somewhere? Or let me know the brand? I'd like to look it up. I think someone told me to get a tripod with round legs, not square. Not sure why, maybe it's more sturdy?

When i get back from school, i'll get the model number, i'm in class now "working hard"