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Author Topic: Yet another "what lens?" question  (Read 5701 times)

elflord

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Re: Yet another "what lens?" question
« Reply #15 on: February 15, 2012, 11:03:06 PM »
Current set up: 60D (yes, I regret not getting the 7D ::)) with 10-22, 15-85, 100 macro, 70-300L. 

You don't have anything faster than f/2.8, so I'd say get a fast prime (f/2 or faster, not one of the new f/2.8 lenses).

Depending on what focal length you prefer, Canon or Sigma 50 f/1.4, Canon 35mm f/1.4 or 35mm f/2, Sigma 30mm f/1.4.

I used the 28mm f/1.8 and wasn't very impressed with it.

I wouldn't recommend getting the 17-55 if that's going to be your fastest lens -- your subject matter calls for fast glass. When the kids are running around, you will probably want to shoot with a flash and smaller aperture, but when they slow down a little, it's nice to have shallow dof and be able to get good shutter speeds without a flash. For shallow dof shots, you need to be a bit careful with the AF (use the center AF point and lock it on exactly where you want to focus)

Given your interest in video, consider keeping the 15-85 (IS is nice to have) and get a fast but inexpensive prime (sigma 30mm f/1.4, canon 35mm f/2) If you're willing to spend more, keep the existing setup and get the 35mm L

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Re: Yet another "what lens?" question
« Reply #15 on: February 15, 2012, 11:03:06 PM »

elflord

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Re: Yet another "what lens?" question
« Reply #16 on: February 15, 2012, 11:12:48 PM »
To dhofmann: Thank you for that link.  I've always liked my 15-85, this has confirmed for me to keep it.

Now another gnarly issue has raised it's head.  The primes being recommended here are both pricey and non-IS. 

The following are relatively inexpensive: sigma 30mm f/1.4, canon 35mm f/2, canon 28mm f/1.8. The 15mm-85mm has IS -- if you keep this, it could be your primary video lens.

DianeK

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Re: Yet another "what lens?" question
« Reply #17 on: February 16, 2012, 12:18:52 AM »

The following are relatively inexpensive: sigma 30mm f/1.4, canon 35mm f/2, canon 28mm f/1.8. The 15mm-85mm has IS -- if you keep this, it could be your primary video lens.


But the 15-85 is only 3.5-5.6 so now I'm really confused.  Do I not need faster for video in indoor ambient light?

Marsu42

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Re: Yet another "what lens?" question
« Reply #18 on: February 16, 2012, 05:21:26 AM »
But the 15-85 is only 3.5-5.6 so now I'm really confused.  Do I not need faster for video in indoor ambient light?

3.5 actually isn't that bad - and the sharpness of the lens doesn't count for video resolution. The problem w/ larger apertures is that the dof is very thin, which means you have to focus-track your subject if it moves. You cannot do this w/ af on eos bodies (well, my 60D at least) since the contrast af is a bad joke, so you have to track your object manually. With anything fast moving and near you, this is only possible with a lot of luck and experience.

And "indoor" doesn't mean much: If you have skylights, the ambient light could be ok, but with one candle in the corner even a 1.8 lens will give you high iso noise.

elflord

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Re: Yet another "what lens?" question
« Reply #19 on: February 16, 2012, 06:13:03 AM »
But the 15-85 is only 3.5-5.6 so now I'm really confused.  Do I not need faster for video in indoor ambient light?

What Marsu42 said -- when shooting video, you're not shooting 18 megapixel frames any more. Even a camcorder or point and shoot (slow zoom lens, small sensor) can shoot decent video indoors. It's not practical to shoot a fast lens wide open all the time indoors because depth of field is shallow. When you're shooting video on a DSLR dof seems more shallow than with stills for two reasons -- one is that you're manually focusing, and two is that the subject is not still, so you need more depth of field to allow for some subject motion. With a still shot, you can lock in on an eye and hit the shutter. If you do that in video and the subject so much as turns their head, you are suddenly out of focus.

What a faster lens would buy you is shallow depth of field for stills. This will help you take pleasing portrait shots. You can always use a flash or two to create some light for yourself, but if you're primarily taking people-pictures, you're really limiting yourself if you can't use an aperture setting faster than f/5.6 at portrait focal lengths.

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Re: Yet another "what lens?" question
« Reply #20 on: February 16, 2012, 06:27:42 AM »
But the 15-85 is only 3.5-5.6 so now I'm really confused.  Do I not need faster for video in indoor ambient light?
Yes, that's recommendable.

Also, a variable aperture is not recommended for video because if you zoom, the video brightness changes. You'd better get a faster lens with a fixed aperture across its whole range, if you want to do serious video. That'd be a +1 for the Canon 17-55 f/2.8 IS.

elflord

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Re: Yet another "what lens?" question
« Reply #21 on: February 16, 2012, 06:31:58 AM »
To summarize, at 35mm focal length, the 15-85 is much sharper wide open (f/4.5) than the 17-55 (f/28).

But that's not an apples to apples comparison. The 15-85 isn't very "sharp" at f/28 !

Quote
You have to stop down the 17-55 to f/4 to get the same sharpness, but then it's only 1/3 of a stop faster.

 What matters isn't how far you need to stop down to reach "the same level" of sharpness, but rather where you need to shoot to attain acceptable performance. While "acceptable" is in the eye of the beholder, there is a broad consensus that the 17-55 is quite usable at f/28.

What you wrote does imply that if you never want to shoot faster than f/5.6, there is no point getting the faster lens, and I'd probably agree with that (in this case). But f/5.6 makes it a pretty slow lens -- that's dof equivalent to f/9 on a full frame, so it basically rules out what would normally be considered large apertures.

Quote
And you lose 2mm at the short end and 30mm at the long end but  gain 2 stops of aperture at the long end.  So the 17-55 is just not a very useful lens unless you want a wider aperture than f/5.6.

The other issue with getting a faster lens is that focusing becomes more difficult unless you stop down, which you can do with a faster lens.

Getting the faster lens doesn't mean that you have to shoot wide open all the time, it gives you the option to use wider apertures. Just as a wide range zoom provides versatility in focal length, a faster lens provides versatility in depth of field

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Re: Yet another "what lens?" question
« Reply #21 on: February 16, 2012, 06:31:58 AM »

neuroanatomist

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Re: Yet another "what lens?" question
« Reply #22 on: February 16, 2012, 07:20:00 AM »
I don't think I would replace the 15-85 with the 17-55, and here's why: http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=398&Camera=474&Sample=0&FLI=3&API=0&LensComp=675&CameraComp=474&SampleComp=0&FLIComp=2&APIComp=0

To summarize, at 35mm focal length, the 15-85 is much sharper wide open (f/4.5) than the 17-55 (f/2.8). You have to stop down the 17-55 to f/4 to get the same sharpness, but then it's only 1/3 of a stop faster. And you lose 2mm at the short end and 30mm at the long end. So the 17-55 is just not a very useful lens.

The other issue with getting a faster lens is that focusing becomes more difficult.

If you read the TDP review of the 17-55mm, there's a statement that the ISO 12233 crops of that lens seem less sharp than Bryan thinks they should.  Also, you're selecting one focal length. At other parts of the range, the 17-55mm is sharper. Overall, across the zoom and aperture range, basically it's a wash between the two lenses in terms of sharpness.  Even if it weren't, sharpness is just one element of lens performance, and offer not the most important (but it is one of the easy ones to measure and gives a number for comparison, so people focus on that, sometimes exclusively).  Consider - the $125 50/1.8 II, when stopped down, is sharper that L-series prime lenses costing 20x as much - if that's your main criterion, you should never spend more than $125 on a lens.

Regardless, to say the 17-55mm is just not very useful simply makes no sense.  At the long end of the 15-85, the 17-55 is letting in 4 times more light.  Also, the DoF with the 17-55mm f/2.8 is shallower than you can achieve with the 15-85mm f/3.5-5.6, for the same framing.  The 15-85mm also has much worse vignetting and barrel distortion.  So, overall, the 17-55mm has slightly better IQ, and f/2.8, whereas the 15-85mm has a larger zoom range. Both are useful, for partly overlapping uses. The 15-85 is a good outdoor walkaround lens, the 17-55 is better indoors, for action where you need a fast shutter, and for portraits.

Finally, I really don't get your last comment. How, exactly, does an f/2.8 lens make focusing more difficult?  For AF, an f/2.8 lens activates the high-precision center AF point found on most Canon bodies, resulting in more accurate and more precise focusing than you'd get with a slower lens like the 15-85mm.  With MF, f/2.8 means a thinner DoF which makes it easier to tell what's in focus and what's not, even if the shot is taken with a narrower aperture.  How is that 'more difficult'?  I suspect what you mean is that f/2.8 can result in a shallow DoF, meaning parts of the scene you wanted to be in focus are outside the DoF - but that's not the fault of the lens, that's the fault of the person holding the camera not choosing an appropriate aperture.  That thin DoF of a wider aperture doesn't have to be used all the time, but having it available is useful.
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The Bad Duck

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Re: Yet another "what lens?" question
« Reply #23 on: February 16, 2012, 09:15:04 AM »
I have no clue when it comes to video but for photos, in low light on a budget I would get a sigma 30 /1.4 or canon 28/1.8 and use it with flash. In low light AF has trouble locking and you might need faster shutterspeeds. Just dial the flash down a bit and use the camera in manual mode; a rather slow shutterspeed of perhaps 1/30 or 1/60 and f/2 or something (at least for the canon). The AF-assist of the flash will help you with focusing, as will the fast lenses. Then if you lack light, the flash will help you. It will also help you freeze action a bit. Then drag the shutter to let ambient light in and set the mood of the scene. Just bounce the flash or use a cord (but then I am not sure about how it will help you get AF locked). Oh and don´t forget to gel the flash to match the ambient light. Practise some and you will find it is rather easy to get the settings right after a few shots.

The canon 28/1.8 is not stellar but when focus is right my copy is sharp in the middle even @f1.8. I don´t think it deserve its bad reputation.

Then of course you have the 50/1.4 from canon and sigma if you want closer portraits. I was never really pleased with the canon 50 /1.4 on my 30D (focus issues) but on my 5DII it really really rocks! I got the canon instead of the sigma because it was lighter.

EOBeav

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Re: Yet another "what lens?" question
« Reply #24 on: February 16, 2012, 09:42:49 AM »
50mm prime, either in the f/1.4 or f/1.8, which ever you can fit into your budget.
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Beautor

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Re: Yet another "what lens?" question
« Reply #25 on: February 16, 2012, 10:05:50 AM »
There's been some great lenses suggested here, especially if you're looking for a prime lens. If you're wanting a zoom, but still want to keep your 15-85 (an awesome lens) maybe check out the Tamron 17-50 F2.8 non-VC (no IS). While it does lack the image stabilization it is a very sharp lens with a fast aperture for an unbeatable price. I bought mine used for $250 locally, and you could probably find a better deal than that depending on your market. A good review of this lens is here: http://www.the-digital-picture.com/Reviews/Tamron-17-50mm-f-2.8-XR-Di-II-Lens-Review.aspx

This lens would be an inexpensive way to try out a fast aperture zoom without having to break the bank. Then if you feel you want something better you can look at the more expensive ones like the Canon 17-55 F2.8.
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Re: Yet another "what lens?" question
« Reply #26 on: February 16, 2012, 01:00:38 PM »
Also, a variable aperture is not recommended for video because if you zoom, the video brightness changes.

... which is of course only a problem if you're using the larges aperture. If the 3.5 dof of a 15-85 is too shallow, you'll be using a smaller aperture anyway, so the variable f doesn't count anymore.

archangelrichard

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Re: Yet another "what lens?" question
« Reply #27 on: February 18, 2012, 09:25:19 PM »
Goto Home Depot (or Sears hardware or Lowes or ...). Get two or three floodlight-reflector-on-a-clamp set ups and 100 to 150 bulbs (they do not need to be too bright). Clamp in convenient locations, they rotate on that clamp so light the room accordingly. Test for brightness (you may need 150 watters)

If this isn't bright enough goto home depot and look at 500 to 1,000 watt halogen worklights (they actually have some on a flexible length of spring that you stand up like a cobra snake or on a tripod (twin head is only $36)

Use 1.8, 2.8 only if you have no other choice; indoor you NEED depth of field, especially to keep fast moving kids (Junior terrorists-in-training) in frame and in focus (f 8 is much better) and zooming to keep up with them is enough trouble - light the room!

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Re: Yet another "what lens?" question
« Reply #27 on: February 18, 2012, 09:25:19 PM »

DianeK

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Re: Yet another "what lens?" question
« Reply #28 on: February 19, 2012, 01:27:41 PM »
Goto Home Depot (or Sears hardware or Lowes or ...). Get two or three floodlight-reflector-on-a-clamp set ups and 100 to 150 bulbs (they do not need to be too bright). Clamp in convenient locations, they rotate on that clamp so light the room accordingly. Test for brightness (you may need 150 watters)

If this isn't bright enough goto home depot and look at 500 to 1,000 watt halogen worklights (they actually have some on a flexible length of spring that you stand up like a cobra snake or on a tripod (twin head is only $36)

Use 1.8, 2.8 only if you have no other choice; indoor you NEED depth of field, especially to keep fast moving kids (Junior terrorists-in-training) in frame and in focus (f 8 is much better) and zooming to keep up with them is enough trouble - light the room!

No need to go to Home Depot, I can simply raid my husband's workshop ;D.  However, busy toddlers and hot halogens on stands may be a recipe for disaster!

Tijn

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Re: Yet another "what lens?" question
« Reply #29 on: February 19, 2012, 01:43:44 PM »
No need to go to Home Depot, I can simply raid my husband's workshop ;D.  However, busy toddlers and hot halogens on stands may be a recipe for disaster!
Expect a lot of noise in those images...  :P

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Re: Yet another "what lens?" question
« Reply #29 on: February 19, 2012, 01:43:44 PM »