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02/04/2004 09:26:27 AM · #1 |
I was inquiring about the Sigma 28-300mm f3.5-6.3 before in another post and was told by EddyG that canon's autofocus supports only 5.6 or larger apertures. So this means that at 6.3, I would need to manual focus to get the correct focus? Or if the camera beeps and autofocuses, should I trust this focus?
Regarding the 6.3, can someone please explain the 2 numbers? F3.5-6.3. From what I can figure, 3.5 would be at the closest focal point of 28mm and 6.3 at 300mm. Is this correct? If so, how does this correlate with the speed of the lense? I'm a bit shady on that part, since in my mind, the aperture mostly refers to a size measurement and not exactly the speed. And why does some lenses only have on F number, does this mean that at all focal lenths, it is the same?
Okay, sorry to make this so long, but I was thinking about getting a Macro lense. I looked at the Canon 50mm f2.8, but it said that it was a 1:2 mag as compared to the 1:1 offered on a similr Sigma lense. Can someone explain this difference in terms of actually taking a picture and getting a result? I read articles about it, but they are really confusing. I just need a simple explanation that I can relate to.
Thanks all,
Kenny
Message edited by author 2004-02-04 09:34:28. |
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02/04/2004 09:30:19 AM · #2 |
| I have Sigma 24-135 mm F2.8-4.5 and focuses extremelly fast and flawless on any focal lenghth.... |
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02/04/2004 09:37:56 AM · #3 |
Yes, Canon's prosumer bodies only autofocus down to f/5.6. Their pro bodies can autofocus with an aperture as small as f/8.
You are correct about f/3.5 referring to the maximum aperture at 28mm and f/6.3 referring to the maximum aperture at 300mm.
When someone says that a lens is "slow", they are referring to the fact that you need longer shutter speeds to compensate for the small maximum aperture. As I stated in my previous example, the difference in shutter speeds between a lens with a 2.8 maximum aperture and a 6.3 maximum aperture is 4X. For a sports shooter, or somebody trying to "stop action", slow shutter speeds are the kiss of death because they result in "motion blur" from the shutter being open too long: either the subject moves, or the camera can't be held steady to get a clear picture.
Focusing speed is another issue entirely. =]
In terms of Macro lenses, the "magnification ratio" is an indicator of how big the object being photographed would appear on the exposed film. A macro lens that can do 1:1 magnification means that if you photographed a macro of a penny, and then took the negative from the camera and set the penny on top of it, the penny on the negative would be the same size as the "real" penny. A macro lens that does 1:2 magnification means the penny would be half as big on the negative.
The advantage of going with a 100mm Macro (which Canon also makes) is that you can be a little farther away from your subject, which is nice if you are trying to photograph living things that react when you get close to them.
Message edited by author 2004-02-04 09:40:18. |
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02/04/2004 09:47:24 AM · #4 |
| Now I undertood,so if the lense is let's say f8 at 400 mm Rebel or 10 D can't focus because is not enough light! |
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02/04/2004 09:51:25 AM · #5 |
There is another advantage to "fast lenses" (lenses that have large maximum apertures -- that is, small f-numbers): the faster the lens, the brighter the viewfinder.
When you are looking through the viewfinder of a 10D/300D/D100, etc., the camera always has the aperture "wide open" to let the maximum amount of light reach your eyes. So when you use a lens that has a maximum aperture of f/6.3, you will only get 1/4 of the light to the viewfinder compared to what you would get if you were using a lens that had a maximum aperture of f/2.8... and 1/8th of the light compared to using a lens with an aperture of f/1.4!
When you depress the shutter all the way to take a picture, the camera very quickly stops the lens down to the appropriate aperture (unless you are shooting "wide-open", which means at the maximum aperture, in which case the aperture doesn't need to change), and then flips up the mirror to expose the shutter/sensor.
You can simulate how "dark" a slow lens looks by using the Depth Of Field Preview button on your 10D or 300D. While holding the camera to take a picture, it is a small button near the bottom front, just to the left of lens mount under the lens release button. Put on a lens, select Av mode, dial in "6.3" as the aperture, focus, and then push-and-hold the DOF preview button. You will hear a slight mechanical noise as the lens is stopped down, and your viewfinder will dim considerably. That is how bright (or dim, as the case may be) a slow lens will normally be. If you try this with something like Canon's 50mm/1.8, the difference is considerable.
In the case of a zoom lens with variable maximum apertures, the viewfinder brightness will change depending on your current focal length.
Message edited by author 2004-02-04 09:58:47. |
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02/04/2004 10:02:51 AM · #6 |
Originally posted by EddyG:
In terms of Macro lenses, the "magnification ratio" is an indicator of how big the object being photographed would appear on the exposed film. A macro lens that can do 1:1 magnification means that if you photographed a macro of a penny, and then took the negative from the camera and set the penny on top of it, the penny on the negative would be the same size as the "real" penny. A macro lens that does 1:2 magnification means the penny would be half as big on the negative.
The advantage of going with a 100mm Macro (which Canon also makes) is that you can be a little farther away from your subject, which is nice if you are trying to photograph living things that react when you get close to them. |
So, with a macro lense like the Vivitar 100mm f/3.5 Macro telephoto lens, the lens would act as a regular fixed length 100mm lens until the adapter is put on for macro shots?
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02/04/2004 10:06:58 AM · #7 |
| Macro means you can come close down to 4-5 inches from the subject and be able to focus. |
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02/04/2004 10:08:56 AM · #8 |
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02/04/2004 10:26:22 AM · #9 |
Originally posted by pitsaman:
Macro means you can come close down to 4-5 inches from the subject and be able to focus. |
I know what macro means, I was asking ifthe lens is only used as a macro lens or does it also function as a regular 100mm fixed lens
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02/04/2004 10:31:03 AM · #10 |
I don't have any direct experience but according to the Lens Performance Survey, it didn't score all that great (scores out of 100, higher is better).
Performance wide open (wide): 61
Performance wide open (long): 53
Performance stopped down to f/8 (wide): 74
Performance stopped down to f/8 (long): 63
Vignetting (wide): 84
Vignetting (long): 84
Distortions (wide): 91
Distortions (long): 87
Color: neutral
Flare: 64
AF Speed: 42
Build Quality: 78
Number of survey inputs: 34
compare and contrast to the Canon 100-400/f4.5-5.6L USM IS:
Performance wide open (wide): 85
Performance wide open (long): 83
Performance stopped down to f/8 (wide): 94
Performance stopped down to f/8 (long): 92
Vignetting (wide): 96
Vignetting (long): 95
Distortions (wide): 97
Distortions (long): 95
Color: slightly warm
Flare: 81
AF Speed: 85
Build Quality: 95
Number of survey inputs: 62
As the saying goes, "you get what you pay for".
Message edited by author 2004-02-04 10:32:02. |
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02/04/2004 10:35:09 AM · #11 |
Originally posted by rickhd13:
I was asking ifthe lens is only used as a macro lens or does it also function as a regular 100mm fixed lens |
Macro lenses on DSLR's do not have "adapters", and yes, they can be used as a regular 100mm lens.
What makes a lens a "true" macro lens is two things: one, it has the optical characteristics that allow it to focus up close, and two, it has very fine focusing adjustment ability, since focusing at macro distances is critical. |
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02/04/2004 02:24:01 PM · #12 |
Originally posted by EddyG:
Macro lenses on DSLR's do not have "adapters |
The Vivitar lens i was asking about does indicate that it has an adapter that when placed on the lens takes the magnification from 1:2 to 1:1
Vivitar 100mm f/3.5 Macro Telephoto AF Lens
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02/04/2004 02:37:59 PM · #13 |
Originally posted by pitsaman:
Macro means you can come close down to 4-5 inches from the subject and be able to focus. |
Macro refers to maginication size, not how close the lens focuses. Anything that is maginfied more than a 1/4 life size is generally refered to as "Macro". Also Macro means that lens focuses at a "flat" plane, where as all other lenses focus at a "radial" plane.
Message edited by author 2004-02-04 14:39:25. |
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02/04/2004 02:51:47 PM · #14 |
Originally posted by rickhd13:
The Vivitar lens i was asking about does indicate that it has an adapter that when placed on the lens takes the magnification from 1:2 to 1:1 |
Interesting. I personally would skip the Vivitar and get something like the Canon 100mm/2.8 Macro or the Sigma 105mm/2.8 Macro which doesn't have that requirement. Both of these macro lenses are very highly regarded by many photographers. |
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02/04/2004 02:54:39 PM · #15 |
Originally posted by EddyG:
Originally posted by rickhd13:
The Vivitar lens i was asking about does indicate that it has an adapter that when placed on the lens takes the magnification from 1:2 to 1:1 |
Interesting. I personally would skip the Vivitar and get something like the Canon 100mm/2.8 Macro or the Sigma 105mm/2.8 Macro which doesn't have that requirement. Both of these macro lenses are very highly regarded by many photographers. |
But check out the price difference :P
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02/04/2004 03:05:47 PM · #16 |
Originally posted by Konador:
But check out the price difference :P |
Price is definitely a factor in my world, but on the other hand, my local camera shop has one of these Vivitar lenses and it produced some very nice prints...
Just something i am kicking around
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02/04/2004 06:47:46 PM · #17 |
It seems like most of you guys like the 100mm macro lenses better than the 50mm. From what I gather, the only thing that really matters would be the maginification ratio of 1:1 (being the best). But does the minimum focusing distance matter? If you were to get really close, wouldn't the image taken be larger than the object or would the maximum be only 1:1?
I am asking because compared to the Sigma 50mm which focuses at 7.4" (inches) with a 1:1 ratio , the canon 50mm focuses at 0.8' (feet) with a 1:2 ratio.
Thus, would it be safe to conclude that you're both going to be able to get closer and also a much larger image than the Canon?
The 100mm Sigma focuses 1:1 at a min distance of about 12 inches I think, so would this image be much larger than the 50 mm?
Also, how does the 1.6X factor of the 10D affect this image size?
I can't figure all this out. If someone would just say that no matter what I do, all my images at 1:1 will be the same size on any macro lense, whether it be 50mm or 100mm because of the min focusing distance, then I would be much relieved, but I somehow don't suspect this is the case.
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02/04/2004 06:57:55 PM · #18 |
1:1 is 1:1 at any focal length lens 50 or 100 or 200 is the same magnification. 1:1 is more magnification than 1:2
The problem with the 50mm is that you will be so close to your subject that you block the lighting. And forget about live subjects.
I have the 100mm canon and love it. Lots of people like thier 105mm sigmas too and they are cheaper.
Tim |
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02/04/2004 07:09:45 PM · #19 |
Originally posted by EddyG:
Yes, Canon's prosumer bodies only autofocus down to f/5.6. |
EddyG, where is the writeup on this? I've used autofocus at F11 before with no problems from any of my lenses. Perhaps I'm taking this out of context? I found no limitations on autofocus on the body. Got a link? Now you have my interest. |
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02/04/2004 07:11:57 PM · #20 |
I see, so you get the same magnification of 1:1 with either the 50 or 100mm lense, it's just that the 100mm would zoom you closer to the subject farther away, yet still be at 1:1 magnification right?
I'm currently planning my future lenses set:
15mm fisheye or superwide f2.8
100mm Macro f2.8
and a 100mm-300mm f3.5-5.6
I plan to use the 100mm macro as my all purpose lense, either that or I buy a very cheap 28-100 mm lense. Anyone think this will be a problem?
My primary photos will be of grand landscapes, far away details, and macro scenes. I am not sure how often the lower focal lenses between 30-100 will be for me, but I think I can probably just get farther away with my 100mm Macro.
Yeah, cost is definitely of a concern for me, that's why I'm trying to figure out my set and not be wasteful.
I have a very very all purpose lense 28-300mm, my first lense, inexpensive but the f6.3 is killing my 10D at the 300mm, the AF can't focus! and i need a tripod for everything indoors... very annoying. Should I just get rid of this lense and get a 100mm macro or a 100-300mm to replace it for the time being? and again, money is a problem right now, unless I am willing to lose 20 lbs in the next month. |
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02/04/2004 07:12:22 PM · #21 |
And to throw more fuel on the fire, there is also the Canon 180mm f/3.5 macro, which is supposed to be even sharper than the 100mm (the MTF graphs certainly support this) and gives an even longer working distance. But costs $1000+. >:(
There's also the MP-E65 macro, which gives from 1:1 to 5:1 magnification (!!) but does not work as a normal lens (is for macro only). Lotsa great choices for the macro junkie!
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02/04/2004 07:23:19 PM · #22 |
5:1 mag i would like to see a shot from that lense.
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02/04/2004 07:24:13 PM · #23 |
| OK, I'm confused now. The Canon specs for the 300D say autofocus range is from .5 to 18 EV. .5 is somewhere between f1 and f13.? at 4 minutes and 1.5 seconds respectivly and 18 is f11-f64, 1/60 at 1/2000 respectivly. |
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02/04/2004 07:24:38 PM · #24 |
The canon 50mm macro(I believe) only goes to 1:2(less magnification)
The 100mm will put you farther away from your subject.
I dont know much about the less expensive lenses.
my main 3 lenses are
24-70L
100macro
100-400L
Tim
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02/04/2004 07:27:50 PM · #25 |
you use them on an olympus?
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