70-200 f4L sharper than 100 f2 at f4

[yltan]

I have been using the 100 f2 for my "small yet sharp" telephoto for some time, together with a 1.4x Tamron converter when I need longer length. Last night I decided to see how good it is, so I took some pictures ( with flash ) at my bookshelf, using the 70-200 f4L set at 100 mm and the 100 mm f2 at f4.

The result ? The 70-200 f4 looks a lot better! At the center, both are about the same, perhaps the 70-200 f4 looks slightly better, but at the right hand corner that I look, there is a distinct difference! See the crop below. I went to look at the left hand bottom corner - same result.

Curious with this difference, I tested my 80-200 f4.5-5.6 - my cheap consumer zoom. Well to say the least, this chap at f11 is much worse than the 70-200 at f4. Well, guess you get what you pay for...

[Citizensmith]

Well the 100 is supposed to be better. In this instance because its a well built prime, and because its stopped down to f/4 wheras the 70-200 is wide open.

My thoughts are...
Focus was off. Did you take one shot or several?
Not sure of the numbers but maybe the 70-200 has a shorter close focusing distance and you were too close for the 100 to achieve correct focus.
Was the 100 definitely at f/4? It looks more like lack or depth of field as the green book is equally sharp in both.
You've got a really bad example of a 100.

Your photos certainly show the 70-200 to be the better lens, and while it is good I'm suprised the 100 is putting in such a weak showing. I wonder whats up?

[yltan]

Well the 100 is supposed to be better. In this instance because its a well built prime, and because its stopped down to f/4 wheras the 70-200 is wide open.

My thoughts are...
Focus was off. Did you take one shot or several?
Not sure of the numbers but maybe the 70-200 has a shorter close focusing distance and you were too close for the 100 to achieve correct focus.
Was the 100 definitely at f/4? It looks more like lack or depth of field as the green book is equally sharp in both.
You've got a really bad example of a 100.

Your photos certainly show the 70-200 to be the better lens, and while it is good I'm suprised the 100 is putting in such a weak showing. I wonder whats up?


I tried several times with the 100 f2 that I had ( it was a used copy that I bought about 2 years ago). The object is 5m away. I check the scale and both the 70-200 and the 100 was at the same spot ( I know, it is not very accurate ). If you think at f4 the 100 was bad, at f2 it was horrible - the corners are absolutely blurred - no words can be read! It could be a DOF type of problem, or my 100mm misfocused ( either front or back focussing ). Strange I never noticed that before! Of course I don't shoot bricks and book shelfs that often... Perhaps I may need to send my 100mm for calibration?

YL

[yltan]

I tried several times with the 100 f2 that I had ( it was a used copy that I bought about 2 years ago). The object is 5m away. I check the scale and both the 70-200 and the 100 was at the same spot ( I know, it is not very accurate ). If you think at f4 the 100 was bad, at f2 it was horrible - the corners are absolutely blurred - no words can be read! It could be a DOF type of problem, or my 100mm misfocused ( either front or back focussing ). Strange I never noticed that before! Of course I don't shoot bricks and book shelfs that often... Perhaps I may need to send my 100mm for calibration?

YL


Not quite correct test. I found that my angle of shooting is somewhat slanted and my books are not quite in line. After retaking the pictures, I found that my 100f2 is quite decent at f2 after all! At f4, it was very sharp, but the 70-200 f4L was very close. It was partly a misfocussing & DOF problem! This makes me feel I shouldn't test all these artificial targets - instead take pictures!

YL

[Citizensmith]

This makes me feel I shouldn't test all these artificial targets - instead take pictures!YL

That's always the theory I've worked on. Nothing at all wrong with analysing your photos to check you equipment is peforming correctly. I just feel its much better doing it in everyday situations. Particularly as they will highlight a lot of issues such as lens flare that these test will never show.

Glad you haven't got a crappy lens as well. :)

[karusel]

It's good that the books are misaligned, that way it is apparent that one of the lenses has backfocused... just look at the books below.

[mbze430]

umm, I think this test is invalid. probably because of focusing.

Look at the first picture. the black books are SHARP, but the green book is not.

Look at the second picture. The green book is SHARP, but the black book isn't.

So this tells a story. Focus on the wrong item, and comparing the wrong subject.

Than the image size. Smaller images will appear sharper than larger ones.

I think this needs to be re-done.