15-85mm or 18-200mm

[NFLD Stephen]

Thanks John. I didn't realize the TS lens' were compatible with extenders; that's good to know. I do have the 1.4 II teleconverter. I still think the 24 would be the best focal length for me...I seem to use that length alot on my zooms.


FYI, here is an example of the distortion in the 15-85....note this was taken pretty much just as an example to see for myself how bad the distortion could be in certain circumstances.[img]/resized-image.ashx/__size/550x0/__key/CommunityServer-Discussions-Components-Files/8/6811.Lens-Distortion.JPG[/img]


This was at 15mm, ISO 100, F8 and 1/50s. Straight out of the camera; no PP. Clearly illustrates the need to keep straight lines away from the edges of the frame when at the widest focal lengths. If you don't use the widest focal lengths and/or keep straight lines near the centre of the frame then the distortion is not nearly so much of anissue. Here is another example:


[img]/resized-image.ashx/__size/550x0/__key/CommunityServer-Discussions-Components-Files/8/5165.Big-Ben-_2600_-London-Eye.JPG[/img]


This was at 24mm, ISO 100, F8 and 1/60s. Minor PP adjustments in DPP. I think this shows less distortion and is acceptable to me as a personal vacation photo (I'm not a pro and just take pictures for my own use).


And of course, when there are no straight lines in the frame at all (ie no buildings) then I don't find the distortion noticable at all. This usually works well for me since where I'm from there are no tall buildings or large cities...just miles and miles of wilderness


Nevertheless, the distortion is the only real issue I have with this lens. But it does detract from one of the key assets of this lens (the wide focal length range) and has me considering other lens. I'd like to justify the 17-55, but I think I would miss the focal length range (both wide and telephoto). If I did that then I'd definately want the 10-22 for the wide end. I've already got the 70-200 F4 IS so the telephoto end is OK. And as mentioned I'd love to have a TS to play with and get some better arch-type shots of some taller buildings!


Lots to consider when next I go lens hunting!


Stephen

[Kayaker72]

R.Acevedo,


Despite the examples of issues with the 15-85, I still recommend it. Really, it is part of "knowing your lens". The 15-85 is very good, not perfect. My experience is that thereis some barrel distortion at 15 mm (3.14% measured by photozone.de), but that it quickly goes away (24 mm they measured 0.581%). My experience the issues with vignetting and barrel distortion diminish by 18 mm (not measured by photozone.de). Also, for comparison to the other lens you mentioned, the 18-200 mm, photozone.demeasured 4.48% barrel distortion at 18 mm.


As a question for Stephen/others, is there more than one type of distortion going on inthe photo of Big Ben at 15 mm? It is certainly extreme. I am wondering ifpart of it is"convergence of parrallel lines"?A perspective issue?


Thanks,


Brant

[Mark Elberson]

Wide lenses are always blamed for "distortion". Although there may be some barrel distortion in the above images I don

[R.Acevedo]

Thanks to everyone for their input. I am definitely going to go with the 15-85. I

[neuroanatomist]

I don't know, Mark... Looking at the first image of Big Ben, I see both perspective distortion (the lean in the clock tower) and barrel distortion (the curve in the clock tower).


Here's an example from my recent trip, shot with the 5DII and EF 24-105mm f/4L IS @ 24mm, which has what photozone.de refers to as 'massive barrel distortion' at the wide end (measured as 4.3%). The left image is a DPP conversion with no corrections applied, the right image is a DxO conversion which corrects for the barrel distortion(DxO also improves the lighting). You can see that the perspective distortion is present in both images, but in the uncorrected image on the left the lines on the ceiling appear to converge (yes, perspective causes convergence too, but not over a distance of 15 feet), the transverse beams on the ceiling 'frown', the vertical columns bow outward, and the altar and table in front appear to 'smile'. Those effects are all due to the barrell dostirtion of the lens, and the spatial correction applied by DxO removes those effects.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/Barrel-Distortion.jpg[/img]

[neuroanatomist]

I am definitely going to go with the 15-85. I'm really looking for a better quality image while still having some freedom of a decent focal range. In time i think I may make a dive for the 17-55 for the wider aperture. Time will tell if will be something I need.

I have the 17-55mm and it's a great lens. But, I wouldn't advise having both the 15-85mm and the 17-55mm in the same kit - too much overlap. I suggest you'd be better off looking to a fast prime after the 15-85mm. Keep in mind that while f/2.8 is the fastest zoom lens Canon makes, an f/1.4 prime lets in 4 times as much light.

[Mark Elberson]

John,


Your example is a much better one. What I

[neuroanatomist]

What I'd like to see is two pictures taken with lenses having different amounts of barrel distortion but in the example itself having zero perspective distortion. If you get bored maybe you could show us since I "think" you have two lenses that would apply

Yep, the 24-105mm @ 24mm vs. the TS-E 24mm which is about as undistorted as you'll find at that focal length. The only examples I have of the same scene shot with both are where the TS-E corrects for both (perspective corrected with shift), but I'll find a bit of time to shoot a straight-on comparison which will isolate the barrel distortion component in a 'real world' setting.

[R.Acevedo]

I am definitely going to go with the 15-85. I'm really looking for a better quality image while still having some freedom of a decent focal range. In time i think I may make a dive for the 17-55 for the wider aperture. Time will tell if will be something I need.

I have the 17-55mm and it's a great lens. But, I wouldn't advise having both the 15-85mm and the 17-55mm in the same kit - too much overlap. I suggest you'd be better off looking to a fast prime after the 15-85mm. Keep in mind that while f/2.8 is the fastest zoom lens Canon makes, an f/1.4 prime lets in 4 times as much light.
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Got ya, thank you. I suppose my 50mm 1.8 would do for now.

[R.Acevedo]

There is also the Canon 18-135 that I forgot about. Any thoughts on that one?