Lenses with large apertures...

I'm pretty new to photography and only been doing it for 2 or 3 months now, but I'm wondering, aren't lenses with very large apertures hard to work with? For example, when using say the EF 200mm f/2L IS USM in low light conditions at f/2, isn't the dramtically shallow DOF such a negative that it outweighs the positive of collecting more light? Sorry if it's a stupid question, I've just been wondering about it for a while so I thought I'd ask!

Thanks for any help!

I'm a beginner and just discovered firsthand how careful you have to be about precise focusing and not moving the focusing plane and that was just @2.8

2.0 must be terribly unforgiving

Stop it down and use flash.

If the condition is that poor, F2 might not even cut it.

Hi, Jack -

It's not a stupid question at all. Yes, shallow DOF is demanding of both the camera (focus calibration) and the operator (particularly problems with slight back and forth movement).

-js

Is that so? I was thinking that that must be the case... I can't see why those lenses command such ridiculous prices, what real advantages do they have?

1.4 @ half an inch of DoF and being able to get the shot is still better than 2.8 and not being able to get the shutter speed fast enough to be hand holdable.

Flash negates this issue altogether but some people don't like to bring an off body flash unit everywhere.

Also, even though the DoF is so thin, the sharpness of the person in focus relative to the blurred background (due to the large aperture) will make the in focus portion way more pronounced.

Jack McEntire wrote in post #8545932
I'm pretty new to photography and only been doing it for 2 or 3 months now, but I'm wondering, aren't lenses with very large apertures hard to work with? For example, when using say the EF 200mm f/2L IS USM in low light conditions at f/2, isn't the dramtically shallow DOF such a negative that it outweighs the positive of collecting more light? Sorry if it's a stupid question, I've just been wondering about it for a while so I thought I'd ask!

Thanks for any help!

Well, it depends.

A photograph generally is better than no photograph, so from that POV even if an eyelash is in focus, that's fine, IMO.

However, DoF increases relatively rapidly at longer distances, which means DoF at 200 F/2 isolates the object, you focused on slightly further away, quite well from the surroundings. For shots of people in low light and relatively busy surroundings, this is a very nice option to have.

Furthermore, when you get into low light shooting, you'll find that you never have enough light, so every little bit, be it aperture or iso, or shutterspeed and IS if you manage to catch still moments, helps.

Large apertures can be hard to work with, but it certainly is fun.

Of course, you don't have to use fast lenses at large apertures only. I tend to use my fast primes more and more for every type of shooting, including landscapes, f.e. The 85L, amongst others, is a great lens for landscapes ...

Kind regards, Wim

Jack McEntire wrote in post #8545968
Is that so? I was thinking that that must be the case... I can't see why those lenses command such ridiculous prices, what real advantages do they have?

you are able to shoot in lower light and you have more control over DOF....i.e., you can blur out the background.

of course it's harder to work with thin DOF because the tolerances for error are much finer.

ed rader

Jack McEntire wrote in post #8545968
Is that so? I was thinking that that must be the case... I can't see why those lenses command such ridiculous prices, what real advantages do they have?

Check the lens sample archives for fast lenses, and you'll know why.

Essentially, fast lenses add another dimension with regard to possibilities, which you don't have when using a slower lens.

Are the prices for these lenses ridiculous? Maybe. However, every f-stop extra increases the lens surface area by a factor two, and the volume by a factor of more than three, and demands much more exacting standards when it comes to lens design and manufacturing. The increase in glass, more difficult design and manufacturing, and the much larger effort required wrt R&D, make these lenses much more expensive. Add to that that more expensive lenses will eb sold less than cheaper, less fast variants, generally speaking, and the law of numbers come in too. IOW, the lens will become even more expensive, because write-off of incurred costs will have to be distributed over less copies of a fast lens than will be the case with a less fast and cheaper lens.

Whether the price then is ridiculous, is in the eye of the beholder. Expensive, yes, worth it, to some, and not to some others.

Kind regards, Wim

Thanks to everyone for the fast replies! I understand it a lot more now, so thank you!

I have another question about lenses if anyone would care to help me out, regarding focal length.

What does focal length mean/matter? Before I started doing photography I always believed that it was the distance at which a lens focuses on a subject, but this can't be true as an 300mm lens doesn't focus on subjects 30cms away from it...

I've done a small amount of research into it and have seen the words 'focused on infinity' (which I REALLY don't understand) used a great deal, and diagrams depicting what I can only describe as varying 'angles of view'. So my question is, what is focal length, and what does it matter?

Once again, sorry for the probably silly question, I'm just a bit confused about it all, lol!

not to mention the 200 f2 with the addition if 2 extenders can save you +/- $8,000 if you were to buy the other zooms seperately lol


I NEED a 200 f2

Jack McEntire wrote in post #8546050
Thanks to everyone for the fast replies! I understand it a lot more now, so thank you!

I have another question about lenses if anyone would care to help me out, regarding focal length.

What does focal length mean/matter? Before I started doing photography I always believed that it was the distance at which a lens focuses on a subject, but this can't be true as an 300mm lens doesn't focus on subjects 30cms away from it...

I've done a small amount of research into it and have seen the words 'focused on infinity' (which I REALLY don't understand) used a great deal, and diagrams depicting what I can only describe as varying 'angles of view'. So my question is, what is focal length, and what does it matter?

Once again, sorry for the probably silly question, I'm just a bit confused about it all, lol!

Focal length is not related to distance which a lens focuses...it is related to the angle of view the lens takes in...much like binoculars...the "enlarged" image magnified nX times the "normal" view...e.g. on the Rebel/xxD cameras, the normal focal length would be about 32mm, so a 320mm lens would be 10x magnification factor...(not to be confused with a 10x zoom factor of a lens from, say, 18mm to 180mm...though the 180mm image is 10x larger than the view at 18mm, it is not 10x the NORMAL view.)

These examples may be easier to understand than my words...

http://www.usa.canon.c​om …nses101/focal_l​ength.html

http://www.kevinwilley​.com/l3_topic03.htm

Jack McEntire wrote in post #8546050
Thanks to everyone for the fast replies! I understand it a lot more now, so thank you!

I have another question about lenses if anyone would care to help me out, regarding focal length.

What does focal length mean/matter? Before I started doing photography I always believed that it was the distance at which a lens focuses on a subject, but this can't be true as an 300mm lens doesn't focus on subjects 30cms away from it...

I've done a small amount of research into it and have seen the words 'focused on infinity' (which I REALLY don't understand) used a great deal, and diagrams depicting what I can only describe as varying 'angles of view'. So my question is, what is focal length, and what does it matter?

Once again, sorry for the probably silly question, I'm just a bit confused about it all, lol!

A focal length is defined as the distance from the centre of a simple lens to the image point of an object at infinity. If you would take a picture, f.e., of the sun at midday, the image of the sun would appear at the distance in mm equal to the focal length, behind the midpoint of that lens, in the image plane.

This is slightly more complex with multi-element lenses like we use in photography, but th eprinciple is the same. Multi-element lenses have several so-called nodal planes, which are planes through the midpoints of the elements in a lens, parallel to the image or sensor plane. The nodal planes that are of importance, are the ones right at the back of the lens, because you can essentially see that as the one "making up" the focal length in a similar way as a simple lens, and the frontmost one, because that determines the working distance, or WD, to the subject you want to photograph.

Lenses of different focal length have a different AoV (Angle of View), IOW, see more or less of the world, with shorter lenses (shorter FL) seeing more, and longer lenses seeing less. This depends also on sensor size, which is why there is such a thing as a crop factor to compare lenses between APS-C and FF, or other formats for that matter.

Finally (for now ), FLs give you a rough indication of magnification factor. A standard lens for FF is ~50 mm, which results in a magnification factor of approx. 1X compared to what humans see themselves. Divide an FL by this standard FL, and it gives you an approximation wrt to magnification compared to the human view. So, a 200 mm gives you roughly a 4X magnification compared to what the eye sees unaided, and a 24 mm approx. 0.5X.

For APS-C you can use 30 mm as a standard FL to determine this magnification as compared to the unaided human vision (note that with 30 mm on APS-C vs 50 mm on FF when applying the crop factor gives you similar results).

Kind regards, Wim

Most advanced photographers I know buy "fast" lenses not for the ability to gather more light but for the shallow DOF you gain.

Thanks again for the fast replies, I think I understand it a lot better now!

I'm wondering though, why are lenses with shorter focal lengths often cheaper than those with longer ones? For example, the [SIZE=2]Sigma 50mm f2.8 is a lot cheaper than the [SIZE=2]Sigma 105mm f2.8. Why is this, and what advantages/disadvantag​es do these lenses have in comparison to each other? I'm thinking of buying one of the two and I'm feeling a bit stuck, so any advice would be much appreciated!