Can the Canon EF 20mm f/2.8's faults be corrected in Post Processing?

henrytd

Since I'm going to be replacing my 16-35 f/2.8L (mark I, purchased years ago with a 10D), I'm considering what options with extreme wide angle lenses will lighten my camera bag, and am considering the Canon EF 20mm f/2.8.

This lens is not favored in a very thorough review at http://www.the-digital-picture.com/Reviews/Canon-EF-20mm-f-2.8-USM-Lens-Review.aspx

But I like it's size, weight and price. So, I'm hoping someone can advise me if I would I be able to correct the distortion and vignetting problems described in this review using post processing tools that are designed to correct problems specifically with this lens.

(This is an equipment question, so I'm putting it here, but I'll understand if it's moved to the Finishing School. Or I could split it into two questions).

My alternative is to spend $300 more and get the 17-40 f/4 L, but it's a bit heavier, and overlaps the function of the 24-70 f/2.8L which I'll be getting to replace my 24-105 f/4 L, since I'm also going to get a 70-200 f/4 to cover the telephoto end of things (daylight grandchildren sports).

I know there are three other 70-200 lenses that are "better", but with the cost and extra weight of the 24-70, I want the lightest and least expensive of these wonderful lenses.

And I do have a 200 f/2.8L, a 100 f/2 and a 50mm f/1.4 for available light that I'll keep (all from pre-digital days).

I'll also be putting my 70-300 f/4.5-5.6 DO in the Fleamarket to help finance the new lenses. I love it, but I just don't use it often enough.

Thanks,

Skip

ziggy53

If this is for the Canon 5D MKII I would easily recommend the Canon EF 17-40mm, f4L USM. Yes, it's heavier than a wide prime but the quality is excellent in the image center throughout the range and wide open and the corners follow at f5.6. If you have to, and if you're not going to be using the lens a lot, you can travel without the lens hood, saving some space. (I use a lanyard cord outside the bag myself to carry larger lens hoods but, I digress.) Flare resistance at 17mm is pretty good even without the hood. Curved diaphragm blades help the bokeh and the 17mm really is visibly wider than 20mm.

For some common applications I even use the 17-40L as a walk-a-round lens on the 5D MKII, cropping into the frame to supply more reach as necessary. The 5D MKII images will easily crop to the same size image as an older 20D/30D/1.6x crop camera with the same number of pixels but better dynamic range. You really can produce a 20" x 30" print from that data for many, if not most, subjects.

An 8" x 10" crop, with the same pixel width 1.6x crop as above, will yield around 10 MPix. That's more than enough for a 300dpi print without interpolation.

aekurth

When I look at the lens list that you intend to replace, I can't figure out what you are trying to accomplish. The 16-35 is a good lens. The 24-105 is a good lens. I would recommend that you keep what you have until you can verbalize what you need in a new lens - different focal length, faster, lighter etc. Then, rent the lens that you think you want to compare it with what you have. Don't depend on reviews you see on the internet. Once you know exactly what you want to accomplish and can demonstrate that the lens you rented will fill the bill, then make a purchase.

ThatCanonGuy

henrytd wrote: »

Since I'm going to be replacing my 16-35 f/2.8L (mark I, purchased years ago with a 10D), I'm considering what options with extreme wide angle lenses will lighten my camera bag, and am considering the Canon EF 20mm f/2.8.

This lens is not favored in a very thorough review at http://www.the-digital-picture.com/Reviews/Canon-EF-20mm-f-2.8-USM-Lens-Review.aspx

But I like it's size, weight and price. So, I'm hoping someone can advise me if I would I be able to correct the distortion and vignetting problems described in this review using post processing tools that are designed to correct problems specifically with this lens.

Vignetting can be corrected in a few seconds with ACR or Lightroom, but do you want to go through that every time for each image? They probably have a batch processing feature, but still.... I don't know how to correct distortion (I'm sure there's a way, just how time consuming is it?).

My alternative is to spend $300 more and get the 17-40 f/4 L, but it's a bit heavier, and overlaps the function of the 24-70 f/2.8L which I'll be getting to replace my 24-105 f/4 L, since I'm also going to get a 70-200 f/4 to cover the telephoto end of things (daylight grandchildren sports).


Skip

Honestly, it depends in whether you're shooting full frame or not. If you're not shooting FF then the 17-40 is better because it's wider. If you are shooting FF (you say you'll shoot youth sports: a 5D2 or similar won't be good for that) then I would recommend the 24 2.8. It gets a much better review on the-digital-picture. Then that would be 24mm, perfect wide-angle. If you want REALLY wide-angle then you're gonna have to either get the 17-40 or sacrifice some image quality with the 20 2.8. The 17-40 is the best option here, in terms of overall quality and the zoom convenience (unless you want the 2.8 aperture).

Actually, I was going to get a 24 2.8 until the folks here convinced me to go for the 17-40

Grainbelt

Proposed:

Swap 70-300 for 70-200 F4
Swap 24-105 F4 for 24-70 F2.8
Swap 16-35 for 20mm or 17-40

If the goal is better telephoto for shooting kids sports, I can see a higher quality telephoto, but why not put it on a crop sensor (7D or used 50D) and leave the rest of the lineup alone?

I would think 70-200 on a 50D and 24-105 on a 5DII would be a cracking combination.

JimKarczewski

I don't see why you would trade the 16-35 for the 17-40. The weight isn't that much different and the difference in quality of images (at least with the MkII, I've never had the MkI 16-35) is quite a bit..... I mean are you really going to notice a 4.5 oz difference? Difference between the 20mm and the 16-35II is about 1/2 lb, so there might be a bit more... but not like you are comparing a 20mm to the weight of say a 300/2.8.

ThatCanonGuy

Yeah, I'm not sure why you want to get rid of that 16-35. If you want better telephoto then keep the 24-105, sell the 70-300, and get either a 70-200 2.8 or a 300 f4 or, for more, a used 300 2.8 non-IS.

henrytd

I've decided what to do. Thanks to all
Thank you Ziggy for your endorsement of the 17-40 f4L. I don't know if it's better than the 16-35 f2.8L (original), but as suggested by the majority of you all, I've decided to keep the 16-35 f2.8 L. At some point I might switch to the 17-40, but it’s not a priority now. Ziggy’s observations definitely convinced me to NOT get the 20mm f/2.8 prime just to save weight, and as TGC pointed out, some of my problems with any wide angle can be corrected in post processing. I just need to learn how to do that.

I agree that both the 16-35 and the 24-105 are great lenses. Crucial to all this is the camera change I’m making that Ziggy spotted: upgrading from the original 5D to the Mark II. That means finding another home for the 5D, and providing the 24-105 as a package seems like a good idea.

And I now will be exploring video, and want the very best lens I can get for the 24 to 70 range. Also the majority of my photography is in this range, and the f/2.8 L certainly meets that objective: twice the light for the viewfinder/LiveView LCD, excellent sharpness, etc. etc.

The loss of IS in that range is not a concern, since despite my age, I have a steady hand and good technique (many hand held shots taken at between ½ and 1/25th of a second without IS that fully meet my needs).

In the short to long telephoto range, I’ve decided on the 70-200 f/4 L IS. Although the IS wouldn’t help for the grandchildren sports pictures, it will help in most everything else. Four stops is claimed for this lens, which is amazing. I sure don’t need to double the weight and pay $800 more for a one stop wider aperture (but I did spend $500 more for the IS vs non IS version of the f/4 lens). (I got in under the 1/8/11 deadline to save $80).

And as suggested, in addition to the 24-105, I will be selling the 70-300 DO ($800?) to help pay the bill. While the IQ doesn’t measure up to the 70-200 lenses, it is amazingly small and inconspicuous, so for street photography and the like it’s ideal. And it has IS.

Grainbelt: I’m doing most of what you suggested. But my days of carrying two SLR’s are over. With the IQ of the 5D II, and the superb L lenses, filling the frame is not crucial: one tenth of the frame will give me a great shot for most purposes.

Unquestionably doing a wedding or other critical assignment, you have to have a backup DSLR, and I always did. Before great zooms, I’d have three cameras hanging from my neck with different focal length primes. But these days my backup is a G-12 (and before that, a G-11, a G-9, an G-7, etc. back to the first one). (And I do have a 10D around somewhere, which I’m told I should convert to IR).

Thanks to all for your helpful suggestions. By mid-week I should have two new lenses, and a new camera that will meet my needs for the next five years or longer (maybe for the rest of my life, who knows?).

Skip

ThatCanonGuy

You say you want to shoot sports, well, I'd say sell that 5D Mark I and buy a 1DIIn with the cash; the 5DII AF is not gonna cut it for sports.

henrytd

Regarding the use for sports photography

ThatCanonGuy wrote: »

You say you want to shoot sports, well, I'd say sell that 5D Mark I and buy a 1DIIn with the cash; the 5DII AF is not gonna cut it for sports.

The large majority of my photography is people and landscapes. Sports is less important. I've used the 5D I for sports, and it was not as good as I'd like, and certainly not as good as the 1D that I sold to raise the cash to purchase the 5D. But, I want and need a 3" LCD with high resolution (not a 2" monitor with 230k pixels), Live View, HD Video, Digic IV, and a camera that weighs 850g instead of 1565g, etc. etc.

While some have complained about the 5D mkII servo focus, I plan to just use the center focus point, and I am expecting a definite improvement over its predecessor. In addition, with AF Microadjustment, one can perfectly calibrate the camera with specific lenses. Also, the specific sports I will be shooting will not involve subjects coming directly at the photographer, which is the biggest challenge for servo focus.

However, the die is cast, and I will report back if I'm wrong about these expectations.

Thanks again for the advice.

Skip