My Canon glass isn't so hot on the 1Ds Mk. III...

Started Feb 2, 2013 | Discussions thread
brightcolours Forum Pro • Posts: 14,924
Wide open map photo??

CanonKen wrote:

These are 1500x1500, 100% crops from the top-left corner of the frame. Shot on a tripod, MLU, shutter cable. The sensor was parallel with the subject (a large, detailed map). Before you ask about focus on the f/2 shot, I even focused on the top corner, locked, and recomposed, same thing. You can still clearly read 'SEATTLE' in the f/2 example, it is just distorted.

First, here is the f/11 shot. I have to say it is AMAZING. To have an old, cheap lens squeeze this sort of detail out of a 20MP FF sensor is a lot to ask for. There is very little abrasion or vignetting.

Here is the same shot at f/2. While you cannot see it, the center of the image is in focus, and the brightness is the same as the f/11 image (with is, the same brightness across the board). My question is, for a lens like this, wide open on a FF body, is this what I should expect? It is OK if the answer is yes. I'm just surprised it is THAT severe. I'm really not trying to pixel-peep, I just want to make sure my expectations are in line.

Your expectations may be a bit off. I can not imagine one wanting to photograph a framed map with a 35mm f2 lens at f2. Not something one would use a shallow DOF setting for!

Try it wide open on a subject that makes sense, (maybe a portrait?) and see if you get what one would be after with such settings (the focussed part in focus, reasonably sharp, and the things in front and/or back of the focal plane nicely OOF, separating the subject from the surrounding clutter.

Same with the 85mm f1.8... No sense in shooting a flat surface at f1.8...

And remember (great bustard has been trying to make this point clear already):

f2 on your 30D is equivalent to f2 x 1.6 = f3.2 on FF. So, compare on a 30D 35mm f2 to 50-55mm f3.2 on FF.

Similarly, compare 85mm f1.8 on 30D to 135mm f2.9 on FF.

That will get you a similar field of view and a similar DOF.

The vinetting on wider lenses (like you see with the 35mm f2) on FF gets stronger due to the nature of FF sensors... The micro lenses on borders and corners can't catch all the light. That is not a problem with the lens, not a problem with the camera, but just normal. you might see similar vignetting with a 30D with an equivalent lens:

35mm / 1.6 = 22mm, f2 / 1.6 = f1.25. But no such 22mm f1.25 lens exists.

Adjust your expectations accordingly (only shoot wide open when it is desired), and you will find that the lenses you have can give pretty nice results with your awesome new 1Ds mk III.

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