Sigma 24-70 f/2.8

[RCOONa]

Rented Sigma 24-70 f/2.8 IQ no better than Canon kit 18-55. Why ?

[RobertTheFat]

Inaccurate focus is one of the major contributors to poor IQ. If the camera you used supports it, did you calibrate the autofocus microadjustment?

[RCOONa]

The T3i does not support micro adjustment. The IQ is not "poor" with either lens, they both acceptable to me, but I was expecting the much more expensive Sigma lense to be much better for me to consider it as an upgrade to the kit lense. Would the Canon 24-70 f/4 give me a better visual difference so that I could justify the cost for a the upgrade ? Side note, I am comparing photos on a 21 inch computer monitor.

[Skirball]

THe kit lens IQ is extremely poor at f/2.8; considering that it can't do it.  That's what you pay for when getting faster, constant aperture lenses.

That said, you either have a really good copy of the kit lens, or a bad Sigma - which happens, and why many people recommend against Sigma if you don't have a camera that does AFMA.  But AFMA shouldn't be a huge deal at f/2.8 unless you got a really bad copy.   As to the kit lens, it's hard to say without seeing an example.  People have different definitions of what is good, ok, and bad IQ.   The kit lens gets a bit of a bad rap, because the test charts show it's mediocre, the aperture is small, the build is poor, etc.  Plenty of people make great photos with a kit lens.  I don't know how good the Sigma 24-70 is.  I know when I upgraded my kit lens to a Sigma 17-70 it seemed much better than the kit, but that might have been in my head.  It wasn't until I got a few prime lenses, and a fast prime, until I saw what a serious jump in IQ does.

[RobertTheFat]

---

@Skirball wrote:

THe kit lens IQ is extremely poor at f/2.8; considering that it can't do it.  That's what you pay for when getting faster, constant aperture lenses.

<chuckle!> I didn't notice that.

That said, you either have a really good copy of the kit lens, or a bad Sigma - which happens, and why many people recommend against Sigma if you don't have a camera that does AFMA.  But AFMA shouldn't be a huge deal at f/2.8 unless you got a really bad copy.   As to the kit lens, it's hard to say without seeing an example.  People have different definitions of what is good, ok, and bad IQ.   The kit lens gets a bit of a bad rap, because the test charts show it's mediocre, the aperture is small, the build is poor, etc.  Plenty of people make great photos with a kit lens.  I don't know how good the Sigma 24-70 is.  I know when I upgraded my kit lens to a Sigma 17-70 it seemed much better than the kit, but that might have been in my head.  It wasn't until I got a few prime lenses, and a fast prime, until I saw what a serious jump in IQ does.

---

But a serious jump in IQ can be wiped right out by a deep crop and the resulting enlargement of the saved portion of the image. Which is why I think that, statistically, I'm better off with good zoom lenses than with primes. Even if I could afford multiple primes, it wouldn't help me much, because so much of my work is under conditions where changing lenses on the fly isn't feasible. There are some in this forum who claim they can juggle three or more good-sized cameras while shooting an event. I'm not one of them.

[Skirball · Accepted solution]

---

@RobertTheFat wrote:

But a serious jump in IQ can be wiped right out by a deep crop and the resulting enlargement of the saved portion of the image. Which is why I think that, statistically, I'm better off with good zoom lenses than with primes. Even if I could afford multiple primes, it wouldn't help me much, because so much of my work is under conditions where changing lenses on the fly isn't feasible. There are some in this forum who claim they can juggle three or more good-sized cameras while shooting an event. I'm not one of them.

---

Sure, though that's another issue well outside of my point - being that you're not going to see a huge jump in IQ going from a kit lens to a midrange zoom.  The differences mostly lie in wider aperture, constant aperture, better AF motor, better build, full frame compatible, etc.  Not that the IQ isn't better, but people expect the performance increase to be proportional to the cost, and it rarely is.  In part because the additional cost is associated with many of the above features as well.  The really noticable difference, in my opinion, are prime lenses.  Where even a moderately priced prime will have a marked difference in IQ. 

As to the prime vs zoom debate.  No need to fully rehash it, but your example is a fairly extreme one that doesn't really offer a fair comparison.  Poor use of a prime in a questionable prime situation such as even photography.  Sometimes primes just don't cut it, and you grab a zoom.  But there's a lot more types of photography than that.  I primarily do studio work, portraiture, product, architectural, real estate, macro, and some landscape.  Buildings don't move, nor does tierra firma, and nothing compares to the resolution of a tilt-shift compared to fixing in post.  Macro photography is almost entirely dominated by primes.  People, even my toddlers, don't move enough indoors that I can't work with a prime.  I'm not saying that zoom doesn't work better for some in these situations, but others of us are quite comfortable with primes. I did some outdoor family shoots last weekend and used nothing but primes, even though I never went below f/2.8.  I just like the flow and sometimes it gets me to crop in closer than I would with a zoom and I often like the result.  It's not for everyone, I understand that, but I wouldn't dismiss primes because of cropping.  I don't crop any more with my primes than I do zoom.

[RCOONa]

Skirball, you have answered my question with your statement that "you're not going to see a huge jump in IQ going from a kit lens to a midrange zoom".  Not having much experience in this area, I guess I was under the impression that going from a cheap kit lense to higher priced lense would improve my IQ enough for me to say "wow, that is a lot better picture", but I guess that may or may not happen. I read in one (KR) review of the Canon 17-55mm f/2.8 IS lense that the reviewer "did not see any more sharpness"  in this $800 lens than in the $200 18-55mm IS II kit lense.  You get what you pay for ? Maybe in build quality, but not a "huge jump in IQ", as you say.  But family and friends looking at my pictures never ask about the build quality of my lense - so if most of that high price don't transalate into picture quality, then what is the sense in the "upgrade".  Thanks for your input, your comments made me think and that is a good thing.  

[ebiggs1]

"...  so if most of that high price don't transalate into picture quality, then what is the sense in the "upgrade"."

The first thing is the poor build on the average "kit" lens will not stand up to pro-level constant day in and ay out use.  They can be pretty good in what pictures they take but if they break than they are useless.  I would destroy a kit lens in a month or two.

If you use your camera once month or just get it out on special occasions, the kit lens is fine.  But if you are like me and use your camera several hours every day the kit lens is a no-go.

I have the Sigma 24-70mm f2.8 and I really like it as it is the smallest lens of this type lens.  I have the EF 24-70mm f2.8 which I consider the best lens in this category.  Primes do not have musch if anything on that lens.  I am a lens junkie as I buy an awful lot of them just for the fun of it.

I will say the Sigma is the worst in IQ in this type lens.  I would rate them in this order:

Canon 24-70mm f2.8 version I and/or II

Tamron 24-70 f2.8

Tokina 24-70 f2.8

Sigamn 24-70mm f2.8

But this is not to say that any of these are not good.  They are and you need heavy crops to see the difference. In real world use, all are fine examples.

IMHO, any of these is a serious upgrade over any of the so-called "kit" lens.

I have done extensive tests of my own to satisify myself comparining lenses, yes, zooms and primes.  A high end zoom can produce results as good or so very nearly as good to be nonexistant.  Sure if you are comparing a kit zoom lens to a average prime you will see the difference.

Was this photo taken with __________ lens?  Not easy to tell, is it?

 

[ebiggs1]

It alos depends greatly on how you intend to use your photos.

[RCOONa]

Thank you ebiggs1 for your valuable input and I certainly agree with your comments as far as they apply to your situation.  But I am not a pro photographer as you are, I don't have a FF camera, I can't afford a Canon L f/2.8, and I have been using the 18-55mm kit lense for two years. I thought it was time to "upgrade" and that is why I rented the Sigma 24-70 f/2.8 - to see what kind of improvement I would see in IQ. As far as the type of pictures I take, I do a bit of traveling and I like to bring home some memories in photos, and I also take flower pictures in my garden.  I find that most of the time I am using the 18-55 lens, and occasionally I use the other kit lense, the 55-250.  I still think I'm ready for an "upgrade" that cost less than a thousand, so I will continue my search.  I prefer Canon, (and it does not have to be 24-70, I just picked that because I could rent the Sigma  locally) but I may have to consider other brands also.  So if you have a couple of recomendations, I would appreciate it. Thx.