September 15, 2014, 12:04:04 AM

Author Topic: Upgrade for 17-55 2.8  (Read 4082 times)

candc

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Re: Upgrade for 17-55 2.8
« Reply #15 on: January 01, 2014, 10:23:46 PM »
If I were to recomend one of the 24-70's I think the f/4 would be an interesting option for its macro capabilities. I haven't seen this reported on but if its .70 mag on ff then it should be more than 1 to 1 on aps-c and give you more working distance.

You haven't seen it reported because that's not how it works.  Maximum magnification is measured at the minimum focus distance - both are intrinsic properties of the lens, independent of the sensor.  It's called a crop factor for a reason.  On APS-C, you're still getting 0.7x mag at the same working distance, but you're capturing a smaller FoV.  Of course, if you back up so you've got the same framing you'd get on FF, you do get more working distance, but in that case you're getting less than 0.7x mag. 

To the extent that your APS-C sensor has higher pixel density, you're getting more pixels on target (digital magnification, as opposed to optical magnification).  If you compare a 5DII and 20D, there's no difference, for example.  If you used the 24-70/4 at the MFD on the full frame Sony a7R (36 MP) you'd get more digital magnification than with that lens at the MFD on the T3/1100D (12 MP), and capture a larger FoV at that 0.7x mag, too.

okay, that makes sense when you think it through. the maximum magnification of the lens refers to the size of the image it projects on the sensor plane. that means the ef-s 60 projects a larger image than the 24-70 at mfd. i was thinking there was some multiplier involved with the 60. like an equivalent to 100% mag on ff. and that the 60mm projected a smaller image on the crop sensor but was an equivalent to the 100mm on a ff sensor but it sounds like the projected image size is the same. its just that the working distance is greater on the 100mm due to the longer focal length?

thanks for explaining

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Re: Upgrade for 17-55 2.8
« Reply #15 on: January 01, 2014, 10:23:46 PM »

Aglet

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Re: Upgrade for 17-55 2.8
« Reply #16 on: January 01, 2014, 10:31:29 PM »
As a few have suggested, the 15-85mm is a very good lens.
It's my most used because of the range, low CA, very sharp, has great IS, fast AF and is no bulkier than the 17-55.  I still have both of these lenses but the 15-85 is nearly welded to my 60D. The 17-55 comes out for some indoor shots or shallower DoF work with my older bodies.
Only complaint i have about the 18-85 is that I sometimes get severe corner shading, likely from a filter I keep on it.  This is intermittent and likely a factor of the IS group being near its physical limit plus the filter not being a super-thin type. Other than that, it's provided 1000s of excellent images and lets me leave the tripod in the car a lot more.

neuroanatomist

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Re: Upgrade for 17-55 2.8
« Reply #17 on: January 01, 2014, 10:54:13 PM »
...it sounds like the projected image size is the same. its just that the working distance is greater on the 100mm due to the longer focal length?

Correct.  At their respective MFDs (for 1:1 magnification), the 60mm, 100mm, and 180mm lenses will all project the same sized image of the subject on the sensor.  The longer FL means two things: a longer working distance (which is why bug hunters like the 180L), and the narrower angle of view with the longer lenses means less of the background is in the image, and what is there is more strongly blurred (stronger background blur, even though the DoF for the subject is the same).
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Promature

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Re: Upgrade for 17-55 2.8
« Reply #18 on: January 02, 2014, 12:53:44 PM »
For what it's worth, I had a T2i and the 17-55 f2.8 and decided to get the 24-105 f4 instead.  I already had the 10-22, so losing the 17-24 range wasn't a problem and losing the 1 stop in appeture didn't really do anything either.  What I got in exchange was (in my opinion) a better walk around lens.  Also, since upgrading the T2i to the 70D, I can honestly stay that the loss of appeture is a complete non issue now with the better low light performance.
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neuroanatomist

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Re: Upgrade for 17-55 2.8
« Reply #19 on: January 02, 2014, 01:47:35 PM »
...losing the 1 stop in appeture didn't really do anything either.  What I got in exchange was (in my opinion) a better walk around lens.  Also, since upgrading the T2i to the 70D, I can honestly stay that the loss of appeture is a complete non issue now with the better low light performance.

More light is just one reason that a wider aperture is beneficial, and you're right that with current cameras, the high ISO performance compensates effectively in many situations.  But, shallower DoF for better subject isolation is another major benefit to a faster lens.
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Promature

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Re: Upgrade for 17-55 2.8
« Reply #20 on: January 02, 2014, 01:59:42 PM »
...losing the 1 stop in appeture didn't really do anything either.  What I got in exchange was (in my opinion) a better walk around lens.  Also, since upgrading the T2i to the 70D, I can honestly stay that the loss of appeture is a complete non issue now with the better low light performance.

More light is just one reason that a wider aperture is beneficial, and you're right that with current cameras, the high ISO performance compensates effectively in many situations.  But, shallower DoF for better subject isolation is another major benefit to a faster lens.

True, true.  But, if I want a walk around lens, I would rather have the range than DoF.  If I want to do portraits, I use my primes.  This of course is just a personal preference.  I'm sure people out there want exceptional subject isolation out of their walk around lens.
« Last Edit: January 02, 2014, 02:05:08 PM by Promature »
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neuroanatomist

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Re: Upgrade for 17-55 2.8
« Reply #21 on: January 02, 2014, 08:41:11 PM »
I'm sure people out there want exceptional subject isolation out of their walk around lens.

Well, I'd call f/2.8 on APS-C more like barely adequate subject isolation, certainly not 'exceptional'.
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Re: Upgrade for 17-55 2.8
« Reply #21 on: January 02, 2014, 08:41:11 PM »