Difference between Sigma and Tamron lens

Looking at the Tamron 28-75 or the Sigma 17-70.

Any thoughts? Thanks.

tawcat wrote in post #13917014
Looking at the Tamron 28-75 or the Sigma 17-70.

Any thoughts? Thanks.

here's a thought: one is primarily for full frame, the other is for crop models
see the reviews at www.photozone.de

Difference? They're different focal lengths, different apertures, and are compatible with different cameras.

The 28-75 is a pretty decent lens. It isn't a L, but it is capable of some really sharp shots. Used my friend's copy several times. Never used or seen a 17-70 before though...

My 28-75 is my workhorse. I got a great copy, sharp wide open and all lengths. Full frame compatible as well. For portraits and general use its a gem. If you were looking for more of a walk-around lens, I think the 17-70 might be better because 28mm isn't as wide as you might want on a crop body.

watt100 wrote in post #13917076
here's a thought: one is primarily for full frame, the other is for crop models
see the reviews at www.photozone.de

Well thanks, but the link you sent did not include the Tamron 28-75. And if I knew the difference I would not have asked.

Seems to me, if I read the descriptions correctly, they both are APS-C lenses. So which of these two is not compatible with my Rebel XS?

tawcat wrote in post #13917504
Well thanks, but the link you sent did not include the Tamron 28-75. And if I knew the difference I would not have asked.

Seems to me, if I read the descriptions correctly, they both are APS-C lenses. So which of these two is not compatible with my Rebel XS?

Your Rebel XS has a APS-C sensor, so both will definitely work on your camera. The Tamron will also work on a FF body, not sure about the Sigma though.

I do love my Tamron, even though it can be annoying when the AF hunts; no issues with the IQ though...

watt100 wrote in post #13917076
here's a thought: one is primarily for full frame, the other is for crop models
see the reviews at www.photozone.de

tawcat wrote in post #13917504
Well thanks, but the link you sent did not include the Tamron 28-75. And if I knew the difference I would not have asked.

Seems to me, if I read the descriptions correctly, they both are APS-C lenses. So which of these two is not compatible with my Rebel XS?

I'm sure you already know this so please don't get offended but just in case you don't know:

Your Rebel XS has a crop sensor and has a crop factor of 1.6x. What this means is, on your camera, the Sigma has an effective focal length of 27-112mm (17-70 x 1.6). The Tamron will have an effective focal length of 45-120mm. Therefor, the Sigma is much better suited to your crop camera as the Tamron is not nearly wide enough for a general purpose lens (on your camera).

I don't know much about these two lenses but the Sigma is probably designed around a crop sensor such as the Rebel so it is likely to perform better on a crop camera even if it was compatible on Full Frame cameras (which I don't think it is)

I was leaning toward the Tamron, but that was my concern, if it was a better fit for a FF. my present lens is a Tamron 18-250, nice lens but really does limit everyday shooting.

I'm sure I'm not indifferent than most, have bought and sold many lenses looking for a good everyday lens. I got tired so I settled on the Tamron.

Thanks for the info and I will probably go with the Sigma.

It's not.

People sometimes say that a lens that is FF-compatible, like this lens or any EF lens, will work 'better' on a FF. This is not necessarily true, and it is simply wrong in this case. When you mount such alens on a crop sensor camera, you lose the outside of the image circle that a FF could capture. That has nothing to do with the quality of the image it does capture.

If you read reviews of that lens, you will find that the only criticism of its IQ is that it can be a tad soft in the corners. On a crop, you don't see those corners. So IMHO, it is actually a better lens for a crop.

I own one and use it a lot on my crop sensor camera. It is my standard lens for indoor candids of people.

Both are good lenses and both will work on your XS. The difference is one may not be wide enough for your needs on a crop camera.

Personally 28mm is not wide enough for me. I do own the sigma 17-70 and it's on my most used lens

All that said, the Tam has an F2.8 and the Sig has an F2.8 - 4. For some reason I thought the 2.8 is better. Am I wrong? Thanks.

tawcat wrote in post #13917014
Looking at the Tamron 28-75 or the Sigma 17-70.

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Any thoughts? Thanks.

difference is....
tamron's better.
:P
But id get the sigma because of its more wide side

tawcat wrote in post #13917923
All that said, the Tam has an F2.8 and the Sig has an F2.8 - 4. For some reason I thought the 2.8 is better. Am I wrong? Thanks.

The tamron has a constant f2.8

The sigma has more focal range, is wider, has an HSM focusing motor, and has optical stabilization.

Like i said both lenses are good lenses bit this is one of those things that if you don't know why you want a lens then you're probably better off just not getting one until you know what you are looking for out of it.

StructuredAmazing wrote in post #13918084
difference is....
tamron's better.

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But id get the sigma because of its more wide side

tamron's is quite wide, i thought, compared to the sigma

tawcat wrote in post #13917923
All that said, the Tam has an F2.8 and the Sig has an F2.8 - 4. For some reason I thought the 2.8 is better. Am I wrong? Thanks.

It seems you may not know some the basics like Aperture and sensore sizes etc so again this is all just in case you don't know. Please don't get offended if you do, it still may help someone who doesn't.

f/xx is used to show the maximum Aperture of a given lens. Aperture is basically how wide the lens will open to allow light to come in. The lower the f/xx number, the wider the lens can open and the more light will be able to enter for a given shutter time. A lens with a wide Aperture is also called a 'fast' lens - reason being you can use a faster shutter speed than a lens with a lower Aperture for the same amount of light entering.

For example, let's say you need to take a picture handholding your camera and your max Aperture is f/4.0, like the Sigma at it's longer focal lengths, and the ideal shutter speed (for the correct exposure) is 1/20th of a second - this will probably lead to a blurry shot (at least a little bit). To get the same amount of light onto your sensor with the Tamron at f/2.8 you will be able to use 1/40th of a second shutter speed because your lens is opening wider and letting more light in which is likely to give you a sharp picture as long as your hands aren't too shaky

So to answer your question, yes a maximum of f/2.8 at all focal lengths is better than one that ranges from f/2.8 to f/4.0. A lens with a variable max Aperture like the Sigma will be able to use its maximum Aperture (2.8 in this case) at its wider focal length (17mm) and it will adjust to a maximum or f/4.0 somewhere along the way to it's longest focal length (70mm). You can usually find out the exact focal lengths at which the max Aperture changes at thedigitalpicture.com.

Of course, whether a constant 2.8 is better than Sigma's widest focal length of 17mm depends on what you are shooting. Sigma also has 2.8 at it's wider focal lengths and even 4.0 isn't HEAPS wider anyway. Also for a general purpose lens 28mm on a 1.6x crop body is not wide enough. Therefor I would choose the Sigma hands down, as long as the IQ is comparable.

Hope this helps