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07-02-2015, 08:48 AM   #1
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Fixed aperture lens question

As I've stated in the title, please forgive the stupidity of this question but I'm an absolute newbiee to photigraphy. My question is this.

If I buy a fixed aperture lens, is there absolutley no way of me manually choosing different apertures when using it.

It's just when reading reviews of lenses such as the D*16-50 it references different apertures, however I was under the impression that it was fixed at 2..8

Cheers

07-02-2015, 08:52 AM   #2
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A fixed aperture zoom lens refers to the construction allowing the lens to maintain the large F2.8 (or whatever) aperture even as you zoom the lens. It does not mean you are stuck with only F2.8, you can certainly stop down to F4, F5.6, F8, F11, etc.
07-02-2015, 09:00 AM   #3
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What JinDesu said ^^. Many zooms are variable-aperture, meaning the aperture closes down as the focal length increases. For instance, the 18-55 kit lens max aperture at 18mm is f/3.5. When you zoom out to 55mm, the max aperture is only f/5.6.
07-02-2015, 09:04 AM   #4
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Ok thanks. This adds a new dimension to my new lens choosing.

07-02-2015, 09:11 AM   #5
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The only true fixed aperture lens you are likely to run into (meaning it really only has one aperture) is a telephoto mirror lens, like a 500mm f/8. Anything else talking about fixed aperture is a zoom lens (not a prime) and it is telling you the maximum aperture stays the same at any focal length of the zoom (which is hard, because it is a ratio). While fixed aperture zooms have an obvious advantage in terms of speed, don't assume a variable aperture zoom is inferior overall. Because it is easier to design a variable aperture zoom, they can be just as good or even superior optically. (Read lots of reviews of whatever you are considering.)
07-02-2015, 09:44 AM - 1 Like   #6
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QuoteOriginally posted by alexorange Quote
As I've stated in the title, please forgive the stupidity of this question but I'm an absolute newbiee to photigraphy. My question is this.

If I buy a fixed aperture lens, is there absolutley no way of me manually choosing different apertures when using it.

It's just when reading reviews of lenses such as the D*16-50 it references different apertures, however I was under the impression that it was fixed at 2..8

Cheers
It was anything but a stupid question. Unlike a lot of other web sites and forums, the folks here really strive to be friendly and there is a lot of information available here on the forum and within the users. Your answer is usually just a post away....

Also - Welcome to the forum!!

07-02-2015, 09:46 AM   #7
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QuoteOriginally posted by interested_observer Quote
It was anything but a stupid question. Unlike a lot of other web sites and forums, the folks here really strive to be friendly and there is a lot of information available here on the forum and within the users. Your answer is usually just a post away....

Also - Welcome to the forum!!

Thanks guys. Much appreciated.
07-02-2015, 10:29 AM   #8
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There are very few lenses where the aperture cannot be changed. One of the few I own is the pentax Q 03 fisheye. It is fixed at f/5.6 and cannot be changed.

07-02-2015, 10:35 AM   #9
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I have always thought that this term was badly named. As mentioned very few lenses are actually fixed aperture. The mirror lenses often are, a few older fisheyes are etc.

The correct term is "fixed MAXIMUM aperture zoom" or "Non-variable aperture zoom" or "constant maximum aperture zoom".
07-02-2015, 12:31 PM   #10
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This has been answered above. However, it's anything but stupid. This is a question I pondered about seven years ago when I was breaking out of my kit lens mode. Most of my best lenses (and add most expensive as well) are constant aperture lenses. I personally like this quality in a zoom lens. Asking a question like this shows growth in a photographer and...is the first step on the road to hell known as lens buying addiction (LBA).
07-02-2015, 01:16 PM - 1 Like   #11
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QuoteOriginally posted by alexorange Quote
As I've stated in the title, please forgive the stupidity of this question but I'm an absolute newbiee to photigraphy. My question is this.

If I buy a fixed aperture lens, is there absolutley no way of me manually choosing different apertures when using it.

It's just when reading reviews of lenses such as the D*16-50 it references different apertures, however I was under the impression that it was fixed at 2..8

Cheers
There are no stupid questions. Only stupid answers, sometimes. Welcome to the Forum.
07-02-2015, 08:18 PM   #12
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Actually, it's a good question and very understandable for a new photographer, especially coming from camera phones which do have a fixed aperture. Cheap P&S cameras in the film era had a fixed aperture as well and maybe some digital P&S's do too although I can't say for sure. Welcome to the forum and don't be afraid to ask questions. That's how we learn and every one of us has had to ask and learn along our journey and most of us, if we are honest, are still learning.
07-02-2015, 08:26 PM   #13
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To reiterate what others have said, it wasn't a stupid question. We call these constant-aperture zooms because the maximum aperture remains the same throughout the zoom range. It's a feature often expected of professional zoom lenses because it often, but does not always, mean consistent optical performance across the zoom range, compared to cheaper consumer-grade zooms which are often f/3.5 or f/4 at the short end but only f/5.6 (or even f/6.3) at the long end. I have the DA* 60-250/4, and it's f/4 maximum throughout the zoom range, but it allows me to stop down to any aperture below that, to a minimum of f/32.

The terminology is a bit confusing here, and I don't blame you for that. Once again, this wasn't a stupid question at all. We take great pride in making this a welcoming and friendly place to talk about photography and Pentax equipment. Welcome to the forums.

—DragonLord
07-03-2015, 12:21 AM   #14
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This thread pretty much sums up why I like to follow this forum.

Seb
07-03-2015, 06:00 AM   #15
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Thanks to everyone. Yes I'm well on my way to lens buying addiction. I'm starting to dream about them. Thanjs again for all the help guys. It's a pleasure being here.
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