What makes one lens better than another for a particular application.
 

Apart from the obvious things that seperate one lens from another like optics, AF, and lens speeds, what makes a lens better at a certain thask than another. What makes an 85/1.4 better than a 50/1.4 for portraits for example?

The 50mm lens shows you what you see with the human eye. The 85mm lens is what the human eye sees, but magnified 1.7 times. The difference is that the 85mm creates more Depth of field verses the 50mm. Also, one disadvantage could be that with the 50mm, you have to get physically close to what you are shooting, but with the 85, you have more versatility with distance from subject. The 85mm is usually thought more of a portrait lens (at least with photographers) and the 50mm more of a general purpose lens. Hope this helps...

awesome. it helps me! :D so i guess it would be safe to say that an 85mm lens would be a good lens to have for portrait work?

Yes, I use an 85mm 1.8 prime lens for portrait photography and it works great! Framing the subject is very easy and you don't have to get up in their face to get a good shot. As for videography???? I have never used a prime lens, so I wouldn't know, but I imagine the same things are true.

I personally think it's more marketing hype than anything about a certain lens being best for this or that. Granted there are some applications where it's obvious that a certain lens/focal length is better than another. But it would seem like a lot has to do with the photographer's own taste and what he/she is trying to accomplish. I've seen portraits taken with focal lengths from 24mm-180mm, they all look stunning. I think it has more to do with the photographer's talent and creativity than focal length. But this is just my take on it.

matt

Matt,

Don't forget that it also has to do with equipment. I recently shot some bridal portraits with a 24-100 zoom and a prime 85. I set the zoom to 85 and took a pic and then put on my 85 and took the pic. The difference was absolutely amazing. Both were Nikon lenses, but the zoom was lesser quality glass.

Also, the general public is very naive and what they think looks good usually wins versus what is creative or talented, which is very, very unfortunate! Some idiot can produce a mediocre picture with great equipment that can "look" better than a very creative one done with less than par equipment. I am speaking generally about those who have no care for art and are concerned with what "looks" good. This is a sad but true fact....it's like the rich fat old man that gets the incredible hot, young blonde...you just don't understand, but sometimes it is just the equipment (money that is).

Clay

P.S. By the way, the bride picked a picture took with the lesser glass zoom lens (B&W) and I was pissed, because I had taken much better shots with the 85mm (Color), but she just had to have B&W.

Regarding the 1st post, not all lenses are created equally. Some are better than others, and many times their cost have little to do with it. Take for example the older Nikon E lenses---some are better (and much cheaper) than some of the Nikkor lenses. I always read the lens reviews on serveral review sites before deciding which lens I should buy.

For portrait stuff, I use my Nikon E 100mm and Nikon E 135mm lenses (the ones with the metal ring).

Clayton,

Does the 85mm give you a magnified image with out compressing like a zoom does?

The reason I'm asking is I'm working on broadening my photographic portfolio and have no experience in shooting portraits, unless you call a shooting a guy 10 feet out of a snowboard halfpipe a portrait.

"Does the 85mm give you a magnified image with out compressing like a zoom does?"

I don't know what you mean by "compressing" the image? The 85mm is fixed glass that magnifies the image like say a telescope. My understanding is that a zoom lens has a magnifying lens (called the magnifier) that moves toward or away from the set lens to create a larger image. There are also other lens within the zoom to help correct for any distortions (usually on the edges) or other problems, like not getting enough light, etc. With the fixed lens, you don't get all of the elements trying to "fix" the zoomed in image, you get an image. Hope this helps and makes some kind of sense...

Clay

I think maybe Adrian is speaking in terms of a digital zoom? If im not mistaken, the canon zoom lenses zoom optically, so I dont think image compression applies to these types of lenses.

But then again, I could be wrong...

Please explain further...

This is incorrect. If the subject stays the same size (either by cropping or adjusting subject to camera distance) the DOF will be the same. If the subject size is allowed to change, DOF decreases with the use of telephoto lenses. That is one reason to use a telephoto for portrait work. The narrower field of view (FOV) also changes the content of the background and can help isolate the subject from the background.

Telephotos also have the apparent effect of compressing distance. If you shoot a portrait with a wide angle, the subjects noise will appear quite large. If the subject is shot again (keeping the head the same size) the nose and other features will appear more natural in size and proportion. DOF will also be the same in both images because the head is the same size

The compression effect can be used to make the model appear thinner. That is one reason models are sometimes photographed with 200mm or longer focal length lenses. Extreme isolation of the subject from the background is also easy to accomplish.

<<<-- Originally posted by Jeff Donald : If the subject stays the same size (either by cropping or adjusting subject to camera distance) the DOF will be the same. If the subject size is allowed to change, DOF decreases with the use of telephoto lenses.

Jeff,

I was referring to if you put a 50mm on in one position and then put the 85mm on in the exact same position with the subject changing size in the viewfinder by use of lens, not by camera distance. Does this not mean that the DOF increases (greater focus contrast between the subject and background)? Have I been led astray?

Also, you don't you think a telephoto lens would be a bit overkill for portraits (intimidating, bulky, legistically difficult)? Or, when you say telephoto are you referring to any lens greater than 50mm? If so, what size would you recommend for portraits? Thanks in advance...

Clay

DOF is a distance of acceptably sharp focus. The distance of sharp focus will decrease as the focal length of the lens increases. Thus, if all factors governing DOF say the same, except focal length, DOF decreases as focal length increases. A complete discussion of DOF can be found here.

I think your confusion is in thinking of DOF as a degree of image blurring. DOF is essentially the opposite.

Telephotos are by definition any lens larger than normal (angle of view the eye sees). Most people consider the 50mm their normal lens. Telephotos may be larger than wide angle lenses depending on focal length coverage and maximum lens opening. Unless working with children, most subjects don't find moderate telephotos too intimidating.

Jeff,

That cleared things up. Yes, my understanding was skewed, but set straight now! Thanks for the link to the great article. Keep up the great work.

Clay

Jeff,

Here's another question for you...since a 10D has a 1:6 ratio, that turns a 50mm lens into an 80mm, and a 200mm lens into a 320mm. But does that refer to magnification power or to image area only? For instance, if you use a 200mm lens, does that simply mean the image area is being cropped to the same image area as a 320mm? Or is there actually increased magnification?