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Author Topic: Sigma 17-50mm F2.8 EX DC OS for Canon  (Read 6673 times)

Offline Scott S

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Sigma 17-50mm F2.8 EX DC OS for Canon
« on: January 31, 2015, 06:12:20 PM »
I wanted to post a quick review. I bought a Sigma 17-50mm F2.8 EX DC OS to replace my 28-75 2.8 Tamron.
17-50 is the equivalent of 28-80 Full Frame. so it's the classic range covered in the past by almost all upgrade wide-tele lenses.
first it's really nice and sharp. the first one I got was DOA and had to be returned, but the second one works stellar. focus is fast and pretty quiet, colors are good. image stabilization is almost unnecessary on a lens this wide unless you're doing macro stuff but then there are other lenses which might be a better choice, but it has it.
how useful this lens will be for you is going to depend on what you shoot. I shoot mostly portraits and events and I find the 17-50 range to be a bit limiting. basically it has the same problem the 28-75 did but in the opposite direction. 28-75 wasn't wide enough, and the 17-50 isn't long enough for a portrait photographer.
with this lens I find myself wanting to change lenses a bit too often. a good 17-85 1.8 or even 2.8 would be the perfect APS-C portrait all around. as it is, I have to jump from the 17-50 to the 70-200 leaving a 50-70 hole right smack dab in the middle of my portrait range. I'm now looking at getting rid of the 28-75 and the 70-200 and getting Sigmas 50-150 2.8. actually, at the moment I'm wondering if I even need that. something like a 35-135 would be better.

so, in conclusion, a classic length lens that's really sharp.

here's a shot taken with it:


Offline exkalibur

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #1 on: January 31, 2015, 10:44:21 PM »
I find it pretty decent for the price but find that it tends to go yellowish on a sunny day (grass and yellow/orange tones are a little strong)
I'm happy 'cause I have a good sense of humor and a short memory ...

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Offline Ochotona

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #2 on: February 01, 2015, 11:27:35 AM »
a good 17-85 1.8 or even 2.8 would be the perfect APS-C portrait all around.

Amen to that.  I wonder why there is nothing like that available?  Seems tecnnically feasable.  I want the canon 15-85 for the range it covers, but it's an f3.5-5.6 which is a bummer and makes me want a 17-50 f2.8, but as you said that is a somewhat limited range.  There just isn't the perfect walk around lens available for APS-C.

Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #3 on: February 01, 2015, 01:04:12 PM »
a good 17-85 1.8 or even 2.8 would be the perfect APS-C portrait all around.

Amen to that.  I wonder why there is nothing like that available?  Seems tecnnically feasable.  I want the canon 15-85 for the range it covers, but it's an f3.5-5.6 which is a bummer and makes me want a 17-50 f2.8, but as you said that is a somewhat limited range.  There just isn't the perfect walk around lens available for APS-C.
If you mean an all around "just in case" type of lens..I think the 18-135 is pretty versatile.
Personally, I kept my 70-200L f4 on my camera at all times unless I knew specifically that I would need another lens for something in particular.
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Scott S

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #4 on: February 01, 2015, 04:42:20 PM »
the big issue with the 18-135 is the aperture. remember on APS-C you have to add 2 stops to get the effective aperture. a 3.5-5.6 is effectively an f 7-11 it's a horrible portrait lens.
they need to make a few pro level L series lenses.

Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #5 on: February 01, 2015, 06:11:33 PM »
Ok a couple of things:
I only mentioned the 18-135 as an "all around lens", not a specific (such as a dedicated portraiture lens) lens. The 18-135 will do many things well but nothing exceptionally well. For portraiture, you would want (I would think anyhow) a lens specific for that purpose to do the best job you could.
Second: can you find some documentation that says you lose 2 stops of light with a crop sensor?? I've never heard that to be honest and have never seen any testing to show this.

In fact, I found this that says just the opposite:
http://www.bobatkins.com/photography/tutorials/crop_sensor_cameras_and_lenses.html
Scroll down to Aperture and then Summing Up.
 
Lastly, Canons L lens ARE pro lens. At least, those L lens are the cream of their crop and arguably as good as anyone elses lens on the market.
« Last Edit: February 01, 2015, 06:46:54 PM by Doodle »
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Scott S

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #6 on: February 01, 2015, 06:53:52 PM »
I'll look and see if I can't find something that explains it better than I'm going to try to do right now, but here goes.
it has to do with the circles of confusion. when you take a photo, the lens is basically a circle through which you are letting light hit the sensor. bigger aperture means bigger hole, means larger circles. larger circles of light coming through the lens from all angles means shallower depth of field, or basically you are focusing on the point where all of the circles of confusion converge on the sensor, with a wide aperture the circles are larger and the point where they converge is much smaller, and the depth of field is much smaller. a tighter aperture is a smaller hole, therefore smaller circles of confusion and greater depth of field.
on paper, f2.8 is f 2.8, 50mm is 50 mm, but not in practice. in the real world, if you have a smaller sensor, you change the angle of view hitting the sensor, so naturally the largest circles of confusion are eliminated entirely, and the depth of field is increased. at the same time, no one says to themselves I want 50mm, you compose how you like to see it and make the camera obey by setting it the way you want. actually a field of view of 50mm on a full frame is achieved on a crop sensor at about 31mm. at 31mm you are at a much wider angle than 50 and all of the things that happen when you use a wider lens happen here. you get a greater depth of field on a wider lens, significantly greater when you consider you're on a 1.6:1 crop factor. the same picture on a full frame camera has a 1.6x larger sensor gathering light, that means 1.6x more light hitting the larger sensor. 1.6x the light is not quite 2 stops. that's just the light that's no longer hitting the sensor because it's smaller. all of this factors in on a crop camera. a smaller sensor means less light hitting the sensor, so you need larger apertures to get the same light, a smaller sensor also means a less effective use of the large circles of confusion resulting in smaller circles of confusion which is like stopping down the lens, again you will need a larger lens to overcome this
2.8 x 1.6 crop = 4.48
3.5 x 1.6 crop = 5.6
5.6 x 1.6 crop = 8.96


Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #8 on: February 01, 2015, 07:04:02 PM »
Rather than edit (again) my last reply, let me amend it with a new post:
I re-read what you wrote about the aperture and realized it was not just about light but could also mean (for portraiture) Depth of Field, or bokeh.  If that is what you meant, then you are probably correct. I still couldn't find anything that said it was a 2 stop difference though but the main point was there IS a difference of DoF for any given length.  It won't be any DARKER, but the DoF would certainly be affected.
But, that then brings me back to the reason I suggested it (the 18-135) at all was your statement of "There just isn't the perfect walk around lens available for APS-C."  Perfect?  That's going to be highly subjective and dependent on each persons need. As a rule though: if you are wanting good portraits, you would use a good portrait lens and not a walk around "Jack of all trades, Master of none" type of lens.
Many portrait photographers prefer a prime (again- subjective as to length) over a zoom. This makes sense as you would probably get a better (sharper) image with a prime.
Walk around lens...almost exclusively...are some sort of zoom to accommodate any given scenario.
Here is a pretty informative article on General Purpose (which is a pretty good description of a walk around lens) lens and none of them were primes. Note that none of them were very long in length either but that goes back to the person's shooting style.
http://www.the-digital-picture.com/Canon-Lenses/Canon-General-Purpose-Lens.aspx
I had to laugh because my suggested walk around lens was not listed at all until the end as a budget alternative. <sigh> Shows how little I know about various lens!
I also noted that the first couple of lens they suggested as walk around lens were pretty damn nice and might actually do well for portraiture (at full zoom though, not at wide angle).
I gotta admit, that 24-70 f2.8 might be fun to try and walk around with.
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Scott S

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #9 on: February 01, 2015, 07:07:29 PM »
a small exerpt from the Bob Atkins thread posted above:

"So the bottom line - and all you really need to know - is that DOF is inversely proportional to format size. Note that format size is inversely proportional to the "digital multiplier". The higher the "digital multiplier", the smaller the format and thus the greater the depth of field. Note also that now you can see one of the reasons large format camera users need tilts and swings to get adequate depth of field. With an 8x10 camera you have about 8.5 times LESS depth of field than you do with 35mm for the same image. This also explains why consumer digicams, some of which have sensors 1/6 the size of 35mm film,  have such a large depth of field and one of the reasons why it's almost impossible to get blurred backgrounds when using them."

Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #10 on: February 01, 2015, 07:12:41 PM »
You aren't changing the quality of light by the crop vs ff, you are just losing surface area. Sure the FF gathers more light due to its size but at f2 it gathers the same AMOUNT on each particular surface. Your example says that if I have 2 cameras using crop and FF...both with duplicate lens and settings...to get the same photo (never minding the size of the image which we all know would be different)...that the crop needs to be set at 2 stops HIGHER to make the same duplicate photo?  I would need a real world example of that because I'm not buying it.
Imagine it raining outside and I take a 6 inch square of cardboard and a 4 inch square of cardboard and hold them out in the rain. Both will get equally as wet but the 6 inch sq will get more water but be equally as wet per sq inch. The 4 inch square doesn't need to be held out longer to get equally as wet. (it would however need to stay out longer to get the SAME QUANTITY of water as the 6 inch)
That crop camera will not be 2 stops underexposed to the FF and that I believe is what you are implying. It WILL have 2 stops (possibly...no hard data yet?) worse in Depth of Field though, which I believe you alluded to.
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #11 on: February 01, 2015, 07:14:16 PM »
a small exerpt from the Bob Atkins thread posted above:

"So the bottom line - and all you really need to know - is that DOF is inversely proportional to format size. Note that format size is inversely proportional to the "digital multiplier". The higher the "digital multiplier", the smaller the format and thus the greater the depth of field. Note also that now you can see one of the reasons large format camera users need tilts and swings to get adequate depth of field. With an 8x10 camera you have about 8.5 times LESS depth of field than you do with 35mm for the same image. This also explains why consumer digicams, some of which have sensors 1/6 the size of 35mm film,  have such a large depth of field and one of the reasons why it's almost impossible to get blurred backgrounds when using them."

That still doesn't say it will be 2 stops less. It applies to DoF only...not aperture size as a whole or it would be affecting exposure...and that's not happening.
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Doodle

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #12 on: February 01, 2015, 07:17:25 PM »
Ok...I just checked your links. You were definitely referring to DoF. On that... I can't argue (although 2 stops?? proof?) as I agree there will always be a DoF degradation on a crop vs FF. But only DoF, not light exposure.
That is where we were not matching up our points I believe.
Take your camera with you dammit. You can't take your next "best photo" if your camera is sitting at home in the bag, now can you?

Offline Scott S

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #13 on: February 01, 2015, 07:19:54 PM »
the Bob Atkins article places it at 1 1/3 stops. I thought it was more, but I'll concede the point.
and you do lose some light, that's why Full frame cameras always outperform APS-C cameras in low light.
one of the things to watch is we're usually trying to achieve the same photo. yes, it you shoot at f2.8 and 1/60 at 50mm on both cameras, you'll see very little difference, but if you adjust the APS-C camera to get the same photo, you do affect the amount of light.

Offline Craig

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Re: Sigma 17-50mm F2.8 EX DC OS for Canon
« Reply #14 on: February 01, 2015, 07:22:11 PM »
Using a light meter my exposure was as follows .......   400 iso, f4.0, 1/160 shutter speed.

Exposure looks the same to me
6D, T2i, Canon 600EX, 430EXII, and some other stuff my wife doesn't know about.