Moon with 55-250IS & 70-300VC

Started Jan 11, 2012 | Discussions thread
tymevest
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Re: Moon with 55-250IS & 70-300VC
In reply to sjwolfhope, Jan 12, 2012

sjwolfhope wrote:

I think it would have been a better comparison if you would have taken both sets of pix at the 250mm setting. My impression is that the Tamron goes a little soft at 300mm, but is still good - your set of pictures shows that. I just finished up a detailed comparison test of those same two lenses at 70mm, 100mm, 135mm, 200mm and 250mm; wide open, f8 and f11; using both one point center focus and nine point focus. This test was done at two different camera to subject distances - one about 12 feet and the other at essentially infinity. Camera is a T1i. The Canon 55-250 lens is a very good performer for it's price. I saw better optical performance (slight in some cases) for the Tamron at almost every test case, except for one point at 250mm, one pt center focus and wide open for the infinity distance subject. I took two shots at each test case and this anomaly was present in both. The nine point focus was better than all the others at the same settings regardless of focus spot. Might have been a hard point to one point focus on that I selected for that shot. The focus point was not adjusted between the two shots per settings. It was set to AF, so it refocused for each shot.

These are just my observations of the Tamron 70-300 VC lens. Wanted to give it a detailed workout before deciding to keep the Tamron and maybe selling the Canon 55-250 lens. I have someone who is interested in it for his first telephoto lens.

Steve W.

One reason I did the test at max FL was to see what the capabilities were. This was not a good test subject because of the moon's phase. The pictures would be much more detailed at a half-moon. But the weather in Ohio doesn't always cooperate.

For better pictures, I would grab the Tamron. I will keep the 55-250 because it's smaller and lighter. For outdoors or walking around, I most always take it. In other test. The 55-250 is sharper at 55mm than the 18-55 is at 55mm even at a larger aperture.

I ran some test with the Tamron and two TCs, the Kenko MC4 (the cheap ones) 1.4x and 2.0x DGX. Both work reasonably well. The lens will autofocus 99% of the time in good light at 300mm with the 1.4x. With the 2.0x, anything past about 150mm is a lost cause so I use it only on a tripod and manually focused.

At full zoom with the 1.4x, it's sharpest at f/13, with the 2.0x at f/18. I tried stacking them and the image falls apart past f/22. Even at f-16-f/20, the image from only one TC enlarged in Photoshop looks noticeably better. I seemed to be able to resolve a bit more detail with the 2.0x than with the 1.4x when it was enlarged to the same size. Either was better than the bare lens when the image was enlarged to the same size as the ones using the TC's.

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Tymevest

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