If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Lenses with fixed aperture
I'm shortly going to upgrade from a compact P&S (Canon S40) to a Canon DSLR
and have been pondering lenses. I find a lot of lenses which have a fixed aperture, such as the well regarded 17-40mm f4 L lens. I'd have thought that fixed aperture would be a bad thing... One of the things about a compact camera is that changing aperture from one end of the range (f2.8 for the S40) to the other (f8 for the S40) really doesn't do a great deal in many cases. I was rather looking forward to working, experimenting and learning with a system that allows a good range of aperture adjustment. But now, in my quest for a small number (like 1 or 2) of quality lenses as a starting point, I find myself homing in on lenses with fixed aperture. Am I right to be concerned about this, or is having a single wide lens fixed at f4 a good thing for reasons I don't understand? -- The email address used to post is a spam pit. Contact me at http://www.derekfountain.org : a href="http://www.derekfountain.org/"Derek Fountain/a |
#2
|
|||
|
|||
Derek Fountain wrote:
I'm shortly going to upgrade from a compact P&S (Canon S40) to a Canon DSLR and have been pondering lenses. I find a lot of lenses which have a fixed aperture, such as the well regarded 17-40mm f4 L lens. I'd have thought that fixed aperture would be a bad thing... 17-40 f4L is a fixed-aperture lens?!?!?!?!?!!? Read a book or something on SLR & lenses. The f4 indicated is the MAXIMUM aperture you can obtain for that lens. But it's not always fixed. The only lenses that i know with fixed aperture are those in cheap point&shoot cameras, and mirror lenses. By the way, the "L" series are the pro lens series on Canon. -- chidalgo |
#3
|
|||
|
|||
chidalgo wrote:
17-40 f4L is a fixed-aperture lens?!?!?!?!?!!? Read a book or something on SLR & lenses. I am, and I'm asking questions when confused. Thanks for the pointer though. -- The email address used to post is a spam pit. Contact me at http://www.derekfountain.org : a href="http://www.derekfountain.org/"Derek Fountain/a |
#4
|
|||
|
|||
"Derek Fountain" wrote in message ... I'm shortly going to upgrade from a compact P&S (Canon S40) to a Canon DSLR and have been pondering lenses. I find a lot of lenses which have a fixed aperture, such as the well regarded 17-40mm f4 L lens. I'd have thought that fixed aperture would be a bad thing... One of the things about a compact camera is that changing aperture from one end of the range (f2.8 for the S40) to the other (f8 for the S40) really doesn't do a great deal in many cases. I was rather looking forward to working, experimenting and learning with a system that allows a good range of aperture adjustment. But now, in my quest for a small number (like 1 or 2) of quality lenses as a starting point, I find myself homing in on lenses with fixed aperture. Am I right to be concerned about this, or is having a single wide lens fixed at f4 a good thing for reasons I don't understand? -- The email address used to post is a spam pit. Contact me at http://www.derekfountain.org : a href="http://www.derekfountain.org/"Derek Fountain/a Fixed aperture, in this case, refers to the fact that the aperture does not change when you zoom the lens, i.e., it will stay at f4, if you set it there, whether you are at 17mm or 40mm, or somewhere in between. Of course, you can set the aperture at anything from f4 to f22 (I believe) and have it stay there. A wide aperture lessens your depth of field, so that backgrounds can be pleasantly out of focus, diminishing distracting details behind your subject. So, the 24-70mm f2.8L can, but doesn't have to, stay at a maximum aperture of f2.8 throughout its zoom range, but the 28-135 f3.5-5.6 IS will be at a maximum of f3.5 at 28mm, f4 by 50mm, f4.5 at 70mm, and f5.6 at 100mm. So you can keep the background more out of focus at the long end with the 24-70 than you can the 28-135. I know it's confusing, I have a "fixed aperture" 400mm (old Canon) FD mount Spiratone "Baseball Bat" telephoto that is permanently set at f8. By the way, small sensors like in the S40 give the lenses a greater depth of field, so apertures don't make as much difference as they do with the larger sensors of DSLRs, or so it seems. -- Skip Middleton http://www.shadowcatcherimagery.com |
#5
|
|||
|
|||
"Derek Fountain" wrote in message ... I'm shortly going to upgrade from a compact P&S (Canon S40) to a Canon DSLR and have been pondering lenses. I find a lot of lenses which have a fixed aperture, such as the well regarded 17-40mm f4 L lens. I'd have thought that fixed aperture would be a bad thing... One of the things about a compact camera is that changing aperture from one end of the range (f2.8 for the S40) to the other (f8 for the S40) really doesn't do a great deal in many cases. I was rather looking forward to working, experimenting and learning with a system that allows a good range of aperture adjustment. But now, in my quest for a small number (like 1 or 2) of quality lenses as a starting point, I find myself homing in on lenses with fixed aperture. Am I right to be concerned about this, or is having a single wide lens fixed at f4 a good thing for reasons I don't understand? For a lens that is (for example) a 24-70mm 2.8 L, the "2.8" simply indicates that the maximum aperture of 2.8 is available throughout the zoom range...which is highly preferable to most consumer zoom lenses that end up giving you a reduced max aperture as you zoom toward the tele end. Remember, this ONLY refers to maximum aperture, and does NOT indicate a limitation of adjusting to smaller apertures. On lesser lenses, you'll see a range of apertures given, but that only indicates how much the **maximum** aperture changes throughout the zoom range. Most zooms allow larger apertures at the wide end of the zoom than at the telephoto end. You can always reduce the aperture to whatever the limitations of the lens is (usually anywhere from f22-f32, or perhaps f64, up to whatever it's max ap is). The only modern lenses (that I'm aware of) that have a TRULY "fixed" apertures (CANNOT be changed) are mirror lenses--which are NOT a good choice for most people, due to their strange rendition of background out-of-focus elements, and highlights. |
#6
|
|||
|
|||
Derek Fountain wrote:
chidalgo wrote: 17-40 f4L is a fixed-aperture lens?!?!?!?!?!!? Read a book or something on SLR & lenses. I am, and I'm asking questions when confused. Thanks for the pointer though. The fixed aperture at f4.0 simply means that the aperture is f4.0 at 17mm as well as 40mm. I do not know of a lens with that short a focal length that is that slow. But I do not know everything. The 17-40 fixed at f4.0 will also allow 5.6, 8.0 and more than likely f 11, and mabey f16. |
#7
|
|||
|
|||
"Derek Fountain" wrote in message ... I'm shortly going to upgrade from a compact P&S (Canon S40) to a Canon DSLR and have been pondering lenses. I find a lot of lenses which have a fixed aperture, such as the well regarded 17-40mm f4 L lens. I'd have thought that fixed aperture would be a bad thing... One of the things about a compact camera is that changing aperture from one end of the range (f2.8 for the S40) to the other (f8 for the S40) really doesn't do a great deal in many cases. I was rather looking forward to working, experimenting and learning with a system that allows a good range of aperture adjustment. But now, in my quest for a small number (like 1 or 2) of quality lenses as a starting point, I find myself homing in on lenses with fixed aperture. Am I right to be concerned about this, or is having a single wide lens fixed at f4 a good thing for reasons I don't understand? The higher priced lenses like the Canon L 17~40 is not a fixed aperture lens, it's a constant aperture lens. This means it stays the same through the entire zoom range. Example when wide open at f:4 it stays f:4 all the way from 17 to 40mm. If I set it at f:8 it stays a constant f:8 through the entire zoom range. A less expensive lens can be f:3.5-5.6 so at 17 it's f:3.5 but drops to f:5.6 at the 40mm end. The TTL light meter will compensate for this, but if I switch to manual, like when I use a studio flash I would have to correct for the offset as I zoom. I hope I have explained this clearly, if not ask and I can try to simplify it more. Darrell Larose Ottawa, Ontario |
#8
|
|||
|
|||
Skip M wrote:
Fixed aperture, in this case, refers to the fact that the aperture does not change when you zoom the lens This sentence straightens out my confusion. } Thanks to you and the others who pointed out the (now obvious to me) concept. -- The email address used to post is a spam pit. Contact me at http://www.derekfountain.org : a href="http://www.derekfountain.org/"Derek Fountain/a |
#9
|
|||
|
|||
"Derek Fountain" wrote in message
... Skip M wrote: Fixed aperture, in this case, refers to the fact that the aperture does not change when you zoom the lens This sentence straightens out my confusion. } Thanks to you and the others who pointed out the (now obvious to me) concept. -- The email address used to post is a spam pit. Contact me at http://www.derekfountain.org : a href="http://www.derekfountain.org/"Derek Fountain/a You're welcome! -- Skip Middleton http://www.shadowcatcherimagery.com |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Aperture fixed when 35mm lenses used on small CCD's?? | Dave | Digital Photography | 25 | January 4th 05 05:36 PM |
Which Maxxum lenses would you recommend? | Lee Howard | 35mm Photo Equipment | 10 | November 9th 04 03:47 AM |
New Leica digital back info.... | Barney | 35mm Photo Equipment | 19 | June 30th 04 12:45 AM |
Vivitar Series 1 lenses and one with sticky aperature | Kevin Butz | 35mm Photo Equipment | 2 | June 26th 04 12:49 AM |
Pentax "K" & "M" Lenses ? | Radio Man | 35mm Photo Equipment | 16 | June 23rd 04 10:23 PM |