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01-10-2010, 09:34 PM   #1
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Okay Guys, Confusing Field of View

Before I went to bed, I tried to do a comparison of the sharpness between DAL 18-55 vs DA 55-300. Keep in mind that these were done on a tripod, and I did not move the tripod between lens changes. Also, both lenses took the shots at 55mm.

Why is it that the 55-300 has a way narrower field of view compared to the 18-55? Doesn't 55mm = 55mm? As far as sharpness, can't tell from the first set, but if you look at the second set, It seems the 55-300 is sharper. But maybe that's because it is zoomed in closer even at the supposedly same 55mm. Still, the sharpness is significantly better for the 55-300, click on it so you can see it better.

LEFT: 55-300 @55 RIGHT: 18-55 @55


Sharpness Comparison
LEFT: 55-300 @55 RIGHT: 18-55 @55



EDIT: When the flyer was shot closer with the 18-55, it was extremely sharp as well, just in the picture above it doesn't seem to be.

Here's the Flyer shot at close range @ 55mm with the 18-55

100% Cropped resized


Thanks


Last edited by joodiespost; 01-10-2010 at 09:56 PM.
01-10-2010, 09:58 PM   #2
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Perhaps because you're shooting at short distances and one lens sticks out farther than the other at 55mm? Just a guess.
01-10-2010, 09:59 PM   #3
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QuoteOriginally posted by Mike Cash Quote
Perhaps because you're shooting at short distances and one lens sticks out farther than the other at 55mm? Just a guess.
yeah, I thought about that and I moved my 18-55 closer by about a foot, and that still doesn't constitute for the massive view field change. hmm.
01-10-2010, 10:09 PM   #4
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It's possible the 18-55 isn't truly a 55 and the 55-300 isn't truly a 55. A mm or two on both lenses could make all the difference.
Now you will have to get a 50mm lens to make comparisons with. I also don't imagine it is as simple as lining up the lenses when taking the shot, they are of two different designs.

01-10-2010, 10:16 PM   #5
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QuoteOriginally posted by joodiespost Quote
Doesn't 55mm = 55mm?
With zoom lenses, sometimes not. They should have close to the same field of view at infinity focus. At other distances, the focal lengths may not be exact because of various optical tricks in lens design. People used to particularily notice this with the DA 18-250. I think that's what's going on. Tomorrow I might see if there's a difference between the kit lens 55mm and my multitude of 55mm primes.
01-10-2010, 10:35 PM   #6
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i see i see.

@ Dave, yeah I'd like to see your shot comparisons too.
01-11-2010, 12:03 PM   #7
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My kit lens is the older version 1, but I don't think that matters. I took boring test shots of subjects at 8 feet and at about 30 miles, comparing several 55mm primes and the kit lens for field of view. I didn't see any changes in the kit lens field of view at 55mm.
01-11-2010, 12:24 PM   #8
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Joseph, I don't suppose there is any chance of operator error in your tests is there?

01-11-2010, 06:55 PM   #9
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If you were to line up a selection of lenses you would find that MOST of them are not exactly "on" the stated focal length. Because of my travels on Craigslist, Efray, and garage sales, etc, etc, I have a number of lenses, some not worth mentioning.

(One good example, shot on my Canon, is the old Tamron Adapt-a-matic 28mm, the Adaptall-2 28mm, and Olympus OM mount 28mm, all three slightly different fields)

During testing to find such things as sweet spots and comparing two lenses for sharpness and so on, I've noticed that MORE TIMES THAN NOT there is a noticeable difference in field of view.
01-11-2010, 07:57 PM   #10
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Gary. Sorry for the late reply, just got home. Yeah the measurements were done without the tripod moving I only switched the lens. I was thinking about it, it might even have to do with the focusing distance. So while the degree of view is the same for both, maybe the 55-300 has to be much furthur away for the same effect. Nothing really bothering though as both these lenses are working fine. Thank guys for the inputs
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