EF lens on crop body. Am I thinking odd?

Hi, I have been wasting nights thinking about which of these lens do I get.
- Canon 50mm f1.8
- Tamron 17-50 f2.8
- Tamron 28-75 f2.8 or Sigma version for 550D.
Just when I was about to freeze on 50mm f1.8 + 17-50 f2.8, I came across a post specifying the impact of EF lens on crop body. In short, it mentioned the crop body would utilise only the centre portion (mostly) of EF lens, given the FOV in crop. In general, we all know centre tends to be sharper than edges, for most of the lens. If that be the case, then is it advisable to buy Tamron 28-75 f2.8 for a crop body. Is it a fair assumption that the combination would deliver 'bigger sharper area' (for lack of word) as compared to EFs lens?

Please teach. Quite often, I do have such odd question but i guess thats inevitable while learning

An EFs lens just has less glass inside of it as it was designed for a crop sensor. That doesn't mean it's less or more sharper or better quality than an EF lens. just that it was specifically designed for a crop sensor. And generally the EFs lenses cost less as they don't have as much polished lens glass inside of them.

Since you'll effectively be cropping the (supposedly) less sharp corners when you use an EF lens on a crop, you may get better corner-to-corner results than with a lens specifically designed for a crop. Of course you'll pay more for equivalent quality (due to the larger size needed), but you'll also have a lens that will work without vignetting if you decide to use it on a full frame camera. I try to buy full-frame lenses because I want them to work on both my T1i and my EOS film body.

There are no "laws of science" against using made-for-FF lenses on crop bodies.

None.

So, if you can afford the more expensive lenses, buy them, and enjoy edge-to-edge better sharpness than FF users.

Regards,

Simon
[Yes, I shoot with two 7D croppers, and yes, I own plenty of EF/made-for-FF lenses]

Pupu wrote in post #14544131
Is it a fair assumption that the combination would deliver 'bigger sharper area' (for lack of word) as compared to EFs lens?

Maybe, but the real question is would 28mm be wide enough for your use on a crop........

In theory an EF lens could be sharper then an "EF-S" lens corner to corner (just remember that third party lenses are not actual EF-S mounts as they do not have the protrusion into the mirror box) However in actual practice I doubt you would see much if any difference in sharpness. In fact with the lenses you mentions you would see worse IQ with the tamrom 28-75 compared to the tamron 17-50.

The way I am looking at my purchases is to get the best lens for my money that will deliver not only what I want now, but what I may be using two years from now. It makes no sense to buy the same thing twice.

<<New owner of an EF 85 1.8

gremlin75 wrote in post #14544406
In fact with the lenses you mentions you would see worse IQ with the tamrom 28-75 compared to the tamron 17-50.

Any particular reason you say this?

gremlin75 wrote in post #14544406
In fact with the lenses you mentions you would see worse IQ with the tamrom 28-75 compared to the tamron 17-50.

Can I ask why you say this? I've owned a Tamron 28-75 for about three years and have used it successively on an XTi, a 40D and now a 7D. It's razor sharp and produces great colour and excellent overall IQ. I use it outdoors and in the studio, and it never lets me down. I'm very happy with it. The range is perfect for portrait photography.

Pupu wrote in post #14544131
If that be the case, then is it advisable to buy Tamron 28-75 f2.8 for a crop body.

No. If you're looking at 17-50's, that means you need a lens in the 17-50 range, not a lens in the 28-75 range.

Buy according to focal length needs, not because of FF or crop.

Sirrith wrote in post #14544735
Buy according to focal length needs, not because of FF or crop.

Buy the glass you want.

Sirrith wrote in post #14544735
No. If you're looking at 17-50's, that means you need a lens in the 17-50 range, not a lens in the 28-75 range.

Buy according to focal length needs, not because of FF or crop.

True, but the beginner with a crop body needs to also keep in mind that when he reads rave reviews about a 28-xx that's being used on a 5d, it will not be a wide angle zoom on his camera. At the wide end he will get an equivalent field of view of a 45mm on a FF. If he needs or wants a wide angle zoom, then he will probably need that 17mm, regardless of whether it's an EF or EF-S compatible lens

Preeb wrote in post #14544901
True, but the beginner with a crop body needs to also keep in mind that when he reads rave reviews about a 28-xx that's being used on a 5d, it will not be a wide angle zoom on his camera. At the wide end he will get an equivalent field of view of a 45mm on a FF. If he needs or wants a wide angle zoom, then he will probably need that 17mm, regardless of whether it's an EF or EF-S compatible lens

I'm not sure how this is relevant to my post?

hold on guys. What focal length I need is a different issue. I do understand the limitations of 28mm instead of 17mm on a crop body. But my question is purely focused on sharp image (rather image with greater sharp area) as a result of using a EF focused lens (not sure if Tamron makes its lenses keeping FF/Crop in mind). If canon EF and EFs is to be compared for that matter.

again > "Is it a fair assumption that the combination would deliver 'bigger sharper area' (for lack of word) as compared to EFs lens?"

I'd say there's a fair chance of it, but it's not guaranteed; making smaller lenses to high precision is easier than larger ones. Probably the biggest thing working in your favor on that assumption is that lenses intended for use on a crop are generally not aimed at professionals, and may not get quite as sophisticated of a design or as tight of tolerances as ones aimed at pros and full-frame cameras.

Pupu wrote in post #14545645
again > "Is it a fair assumption that the combination would deliver 'bigger sharper area' (for lack of word) as compared to EFs lens?"

That is a safe and fair generalization. As one who owns a crop-factor camera, I have been upgrading/replacing my EF-S glass with EF over the past year (and glad for it).