Question on aperature and ISO

[Apo11o]

I'm somewhat new to the whole Photography scene, so I have a lot to learn. However, from browsing forums and websites, I've concluded a few things:
1. photographers strive for quality in their photographs
2. the larger a lenses aperture, the pricier the lens
3. low ISO gives the best quality and greatest reduction of noise.

from these things, I've kind of assumed that pictures taken with a higher aperture and a lower ISO (generally) produce the best quality.. but no where online has someone said that outright. Is this true to some extent? What exactly separates my stock xti zoom lens from a $200 50m lens? Also, how can the optics provide a cleaner, crisper picture?

I know they are broad questions, but i'm really curious. Thanks for your help!

[Crossfire]

Couple of things, the larger aperture lenses (range from f/1.2 - f/2.8) are generally more expensive because most (not all) are part of Canon's L series (professional grade) lenses. The build quality of these lenses is superior to non-L lenses. Also the L series zoom lenses have a constant f/2.8 max aperture throughout the range, whereas the maximum aperture for non-L lenses will vary between the wide and telephoto end. Having a maximum aperture or 2.8 or more has huge advantages when shooting in low light (you can shoot at higher shutter speeds) and also provide greater options for creative images. That's why they cost more

What most people find is that images are usually sharpest when the lens is stopped down a couple of stops from the maximum aperture (commonly known as the 'sweet spot'), i.e. a lens is generally not at its sharpest when shot wide open (much shallower depth of field).

[Apo11o]

Well that seems to make sense. I figure if your setting up a portrait shot with sufficient lighting, then a wider aperture is the way to go. It sounds strange that the wider the aperture is the less noise and the cleaner the image will be.. when the "sweet spot" is a few stops down from the maximum aperture. Maybe i'm just looking at it in the wrong way.
Another thing i've come across is that prime lenses are generally better for portraiture as they produce cleaner pictures, but apparently they are harder to focus. How does this work? Should a first lens for portraiture be a zoom lens, or a prime?

[elysium]

I'm somewhat new to the whole Photography scene, so I have a lot to learn. However, from browsing forums and websites, I've concluded a few things:
1. photographers strive for quality in their photographs
2. the larger a lenses aperture, the pricier the lens
3. low ISO gives the best quality and greatest reduction of noise.

from these things, I've kind of assumed that pictures taken with a higher aperture and a lower ISO (generally) produce the best quality.. but no where online has someone said that outright. Is this true to some extent? What exactly separates my stock xti zoom lens from a $200 50m lens? Also, how can the optics provide a cleaner, crisper picture?

I know they are broad questions, but i'm really curious. Thanks for your help!

Interesting topic. Just like to elaborate on this if I may.

1. photographers strive for quality in their photographs
Always. What good is it to do anything with the same results. Like everything, creativity helps to bring new ideas but without quality, you can lose the impact of what you are after.

2. the larger a lenses aperture, the pricier the lens
Yes but sometimes it is necessary. It gives you more option of depth of field but mainly helps you to shoot in lower lit conditions with much ease. Wedding photographers may really prefer primes due to this, just depends on your line of work. Not everyone will always look at them but the option is there.

3. low ISO gives the best quality and greatest reduction of noise.
Yes once again true however you can have a good quality image if you nail the exposure correctly even at high ISO's. Some noise reduction can be done to remove this or resizing.

Sometimes the noise can help to make a picture have a bit more depth and feel.

[airfrogusmc]

Couple of things, the larger aperture lenses (range from f/1.2 - f/2.8) are generally more expensive because most (not all) are part of Canon's L series (professional grade) lenses. The build quality of these lenses is superior to non-L lenses. Also the L series zoom lenses have a constant f/2.8 max aperture throughout the range, whereas the maximum aperture for non-L lenses will vary between the wide and telephoto end. Having a maximum aperture or 2.8 or more has huge advantages when shooting in low light (you can shoot at higher shutter speeds) and also provide greater options for creative images. That's why they cost more

What most people find is that images are usually sharpest when the lens is stopped down a couple of stops from the maximum aperture (commonly known as the 'sweet spot'), i.e. a lens is generally not at its sharpest when shot wide open (much shallower depth of field).

Another reason SOME Ls cost so much is they have SPECIAL elements like aspherical and fluorite which are expensive to produce but cut down on (aspherical element) spherical aberration and fluorite in some long telephoto lenses chromatic aberration.

[Jon]

I'm somewhat new to the whole Photography scene, so I have a lot to learn. However, from browsing forums and websites, I've concluded a few things:
1. photographers strive for quality in their photographs
2. the larger a lenses aperture, the pricier the lens
3. low ISO gives the best quality and greatest reduction of noise.

from these things, I've kind of assumed that pictures taken with a higher aperture and a lower ISO (generally) produce the best quality.. but no where online has someone said that outright. Is this true to some extent? What exactly separates my stock xti zoom lens from a $200 50m lens? Also, how can the optics provide a cleaner, crisper picture?

I know they are broad questions, but i'm really curious. Thanks for your help!Image quality is affected both (but separately) by the lens and the sensor. You want a low ISO to get best results from the sensor. You want the lens' optimum aperture for best results from the lens. Sometimes these two leave you working at cross purposes; you can't get the aperture you want to use for best IQ without using a higher (and noisier) ISO setting to get a usable shutter speed.

Actually, large aperture lenses are more expensive, L or not, because it's much harder to correct for the aberrations you get with the big chunk of glass needed to get that large aperture. To take it to an extreme, consider a pinhole camera - absolutely no glass, so dirt cheap to make. Make the opening a bit bigger and watch the image fall apart. So you need to start using glass to bend the light and pull it back together. And the bigger the opening (aperture) the more glass you need to add. Unfortunately, the more you bend the light, the more chance the light has to get bent unevenly. So you need to add more glass to correct for that. And so on. Alternatively, you can use exotic glass, other optical materials, or complexly-curved lens elements, which also help control the bending.

What makes L glass expensive isn't just the optics though, it's also the mechanical and electrical build quality; they're more solidly built, are often weather-sealed and have faster-performing motors.

Well that seems to make sense. I figure if your setting up a portrait shot with sufficient lighting, then a wider aperture is the way to go. It sounds strange that the wider the aperture is the less noise and the cleaner the image will be.. when the "sweet spot" is a few stops down from the maximum aperture. Maybe i'm just looking at it in the wrong way.
Another thing i've come across is that prime lenses are generally better for portraiture as they produce cleaner pictures, but apparently they are harder to focus. How does this work? Should a first lens for portraiture be a zoom lens, or a prime?Depends on your style. For studio portraiture, where you're working in a closely-controlled environment (whether in a classical studio or not), where you can control your separation from the subject, a prime would be the better choice; you can set up the framing you need, and you'll usually have a broader range of available apertures (and a larger starting aperture, which means the "sweet spot" will also be larger). If you're more typically doing environmental portraiture, where you have less control over the setting and set-up, a zoom will give you back much of the compositional control you sacrifice by giving the subject free rein.

Remember, though, the separate contributions of the sensor and the lens to final IQ. Noise (from high ISOs) will be throughout the picture, and more apparent in the darker areas. The lens' contribution to the overall image quality will be more apparent around the edges, in the case of aberrations, and in OOF areas in the case of bokeh. Stopping down will reduce the aberrations, but reduce the areas where bokeh is present. Bokeh, on the other hand, by producing a pleasing degree of blur, can mask many of the aberrations you might otherwise see.

[Apo11o]

Wow, thanks for the help everyone! I'm tying to read and ask around as many questions as I can, since getting different peoples opinions and experience seems the best way to learn. As of now, it's safe to say that my main interest is in portraiture, both composed and environmental. I plan on setting my camera up focused on an object and taking pictures that go through all the stops under each priority, so I can see exactly the image thats being produced and find that sweet spot i've been hearing about. I generally think less noise and strong blur is the way to go, which would require a low ISO and a wide aperature, so maybe a prime lens would be worth it. Oh well, i'm only a college student and I ain't loaded, so I'll have to be patient.

[elysium]

Wow, thanks for the help everyone! I'm tying to read and ask around as many questions as I can, since getting different peoples opinions and experience seems the best way to learn. As of now, it's safe to say that my main interest is in portraiture, both composed and environmental. I plan on setting my camera up focused on an object and taking pictures that go through all the stops under each priority, so I can see exactly the image thats being produced and find that sweet spot i've been hearing about. I generally think less noise and strong blur is the way to go, which would require a low ISO and a wide aperature, so maybe a prime lens would be worth it. Oh well, i'm only a college student and I ain't loaded, so I'll have to be patient.
Also put your location on your profile. Will help people to know where you are based to be able to give you answers to questions about where to buy etc.

[airfrogusmc]

Wow, thanks for the help everyone! I'm tying to read and ask around as many questions as I can, since getting different peoples opinions and experience seems the best way to learn. As of now, it's safe to say that my main interest is in portraiture, both composed and environmental. I plan on setting my camera up focused on an object and taking pictures that go through all the stops under each priority, so I can see exactly the image thats being produced and find that sweet spot i've been hearing about. I generally think less noise and strong blur is the way to go, which would require a low ISO and a wide aperature, so maybe a prime lens would be worth it. Oh well, i'm only a college student and I ain't loaded, so I'll have to be patient.

Thats the kind of work I do almost every day.

My cameras are 2 5Ds (no grips)and a 24 1.4L, 35 1.4L and 85 1.2L.

I'd rather have a few great lenses of focal lengths I use all the time than a bag full of glass...

Saves money in the long run...

I shoot allot at high ISOs. The 5D is great at it if you expose properly.

[Apo11o]

Thats the kind of work I do almost every day.

My cameras are 2 5Ds (no grips)and a 24 1.4L, 35 1.4L and 85 1.2L.

I'd rather have a few great lenses of focal lengths I use all the time than a bag full of glass...

Saves money in the long run...

I shoot allot at high ISOs. The 5D is great at it if you expose properly.

Thats quite an arsenal! I've got myself an xti. I wish I was content with it, being my first camera and all, but it just doesn't produce the pictures I want it to. Gah, what I'd do for a 85 1.2L... could you loan me a grand? :P

[EOS_JD]

Buy understanding Exposure by Bryan Petersen. A great read and will help you understand the relationship between shutter speed, aperture and ISO.

[Cody21]

ditto ... great book to get grounded on those concepts. The light bulb will go on.