Fast prime lens question

[Lazy Photographer]

Through following the forum and other resources I've been hearing a lot about prime lenses. Many seem to be fans of the 50mm F1.8 primes. So here's my question (don't laugh, I'm new):

I've heard that a low F stop such as 1.8 will give you a very shallow depth of field. If that's the case, doesn't that really limit your use of those prime lenses fixed at 1.8? Or am I totally missing something here?

 

[Josh66]

It's not fixed at 1.8, that's just the maximum.

 

[Lazy Photographer]

Well that sure changes the picture (excuse the pun). I'm used to seeing lens specs list aperture range from max. to min., so I assumed the primes were fixed, since they don't list the min. Thanks for clearing that up.

 

[Plato]

Through following the forum and other resources I've been hearing a lot about prime lenses. Many seem to be fans of the 50mm F1.8 primes. So here's my question (don't laugh, I'm new):

I've heard that a low F stop such as 1.8 will give you a very shallow depth of field. If that's the case, doesn't that really limit your use of those prime lenses fixed at 1.8? Or am I totally missing something here?

As you've already been told, it's not fixed. That's the maximum. However, when you do shoot wide open, it allows you to keep the subject in focus with the background blurred. The subject really pops out.

Here are some snapshots that will give you an idea of what I'm talking about. Roughly 1/3 of the shots were taken with 50mm f/1.4 or 85mm f/1.8 wide open.

 

[Josh66]

The reason primes only have one number listed is because they don't zoom.

Some zooms have a constant maximum aperture throughout the range... Many have two listed though.

When you see two maximum apertures listed, the first one is for the wide end of the lens, the second one is for the long end.

 

[Lazy Photographer]

Thanks. Checked out the photos. Nice work.

 

[Lazy Photographer]

Thanks. I think I've got it now. One other thing: Why are folks so hot on the 50mm? I mean, that's not very wide, is it? Isn't that somewhere in the range of 75mm after the crop factor is considered? I would think something like a 20mm would make more sense, no? Of course, I realize there's likely hundreds of dollars difference between the two sizes, but is that the only reason, because they're relatively inexpensive for a fast lens?

 

[Plato]

Thanks. Checked out the photos. Nice work.

The sunrise is really beautiful. Do you have to get up early to take shots like that?

 

[Samanax]

Thanks. I think I've got it now. One other thing: Why are folks so hot on the 50mm? I mean, that's not very wide, is it? Isn't that somewhere in the range of 75mm after the crop factor is considered? I would think something like a 20mm would make more sense, no? Of course, I realize there's likely hundreds of dollars difference between the two sizes, but is that the only reason, because they're relatively inexpensive for a fast lens?

The 50 f/1.8 is inexpensive and you can use it for low light situations, when you want a shallow DOF (to isolate the main subject from the background) and it's also used as a portrait lens by some. It's just a nice focal length to have.

 

[Lazy Photographer]

Thanks. Checked out the photos. Nice work.

The sunrise is really beautiful. Do you have to get up early to take shots like that?

I assume you're talking about the photo I posted on my blog. Yeah, that was indeed EARLY. Got up for a piss around 5 and next thing I know I'm in my car heading for the hydro corridor. It was dark when I started. Took like 200 shots over the course of an hour. It was fun. You can check out the four photos I originally posted that morning here. Thanks, by the way.

 

[Lazy Photographer]

Thanks. I think I've got it now. One other thing: Why are folks so hot on the 50mm? I mean, that's not very wide, is it? Isn't that somewhere in the range of 75mm after the crop factor is considered? I would think something like a 20mm would make more sense, no? Of course, I realize there's likely hundreds of dollars difference between the two sizes, but is that the only reason, because they're relatively inexpensive for a fast lens?

The 50 f/1.8 is inexpensive and you can use it for low light situations, when you want a shallow DOF (to isolate the main subject from the background) and it's also used as a portrait lens by some. It's just a nice focal length to have.

Yeah, I guess. I usually like wide angle stuff so for me it would probably not be wide enough. Something fast that zooms would be nice, like 20mm-60mm. I got a feeling it don't come cheap.

 

[TUX424]

For that you are looking at a 24-70 f/2.8, they range from $600-$1700.

 

[camz]

Well it's said that the human eye has the equivalent focal length of around 35mm relative to a full frame. So considering a 20mm focal length would be almost similar factoring in your crop factor of 1.5x~1.6x. Anything less the focal length of a human eye would be considered a wide angle lens. So having a prime wide angle lens you will end up zooming in more with our feet...offcourse depending on the application but it caters to a more specific type of photograhy.

Now the typical 50(nifty fifty?) that you speak of is quite popular because of it's diverse capabilities for portraits, street photography, landscape you name it. Since it falls somewhere in the standard~telephoto focal length(depending on your camera body) it can be used on a wider spectrum of photography.

It's very cheap simply because of this reason-it's standard. Once you go outside the scope of a normal focal length..wider or telephoto manufacturers will need more glass to manipulate the image resulting to more cost of the materials.

So to answer your question about it being wide or not...it really depends what your going to be shooting.

 

[DScience]

Well that sure changes the picture (excuse the pun).

LOL :lmao: Nice one