Is my 55-250 broken?

Started Aug 16, 2011 | Discussions
treepop
treepop Contributing Member • Posts: 723
Is my 55-250 broken?

I was comparing my 55-250 to my 18-135 and noticed a big problem. 135mm on my 18-135 was equivalent to 96mm on my 55-250. Additionally. The 55-250 is exceptionally more blurry than the 18-135, which shouldn't be the case at all.

Please look at my pictures. I shot them with a tripod, IS off, and 2 sec delay shot.

I will look to see if 18mm and 55mm match my other lenses, but I am pretty sure the 55-250 is broken and needs to be sent in.

Of course I am a photography noob, so any input would be greatly appreciated.

Thanks

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Jon_T
Jon_T Veteran Member • Posts: 4,061
Re: Is my 55-250 broken?

treepop wrote:

I was comparing my 55-250 to my 18-135 and noticed a big problem. 135mm on my 18-135 was equivalent to 96mm on my 55-250. ...

Depends on the camera to subject distance. Not unusual with the wide-tele zooms that the max tele focal length is only when focused at infinity. As the distance between the camera and the subject decreases, the effective focal length decreases. Would not be surprised if you may notice the same effect comparing the 55-250 with a fixed 200mm tele lens.

... Additionally. The 55-250 is exceptionally more blurry than the 18-135, which shouldn't be the case at all. ...

Curious as to what's your reason(s) you would think that? This subject was discussed in your similar previous thread: http://forums.dpreview.com/forums/read.asp?forum=1029&message=38938907

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Gene L. Veteran Member • Posts: 3,788
Re: Is my 55-250 broken?

The field of view is affected by the focal distance. As you increase the distance from the subject expect the two lenses to become more similar in terms of field of view.

Though the 55-250 is a bit softer, I don't see exceptionally blurry. How does it perform at other focal lengths?

treepop wrote:

I was comparing my 55-250 to my 18-135 and noticed a big problem. 135mm on my 18-135 was equivalent to 96mm on my 55-250. Additionally. The 55-250 is exceptionally more blurry than the 18-135, which shouldn't be the case at all.

Please look at my pictures. I shot them with a tripod, IS off, and 2 sec delay shot.

I will look to see if 18mm and 55mm match my other lenses, but I am pretty sure the 55-250 is broken and needs to be sent in.

Of course I am a photography noob, so any input would be greatly appreciated.

Thanks

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Steve Balcombe Forum Pro • Posts: 13,226
Re: Is my 55-250 broken?

treepop wrote:

I was comparing my 55-250 to my 18-135 and noticed a big problem. 135mm on my 18-135 was equivalent to 96mm on my 55-250.

Already mentioned by the others, but just to give a fuller explanation:

At the simplest level, focusing a lens consists of moving the optics closer to the sensor for distant subjects and further from the sensor for close up subjects. That's why many lenses extend when focusing. However, many others focus by moving internal elements, and this can have a 'zooming' effect, making the focal length shorter (usually) when focusing closer. It's a trade-off - sure we would all prefer to retain the full 'reach' of the lens throughout the zoom range, but internal focusing is generally better for at least three reasons. It keeps the lens more compact in use; it reduces the size and weight of the glass which has to be moved by the focusing mechanism; and it allows for better correction of aberrations at close focusing distances.

The focal length specified in the description of a lens - "55-250 mm" etc. - is always the focal length when focused at infinity. This is also the focal length reported in the EXIF data, and it is not adjusted for focusing distance, so it is often incorrect.

Because the actual focal length shortens when focusing closer, we can say that the 'problem' you see is not that the 55-250 is reporting 96 when it should be 135. It's the opposite - the 18-135 is reporting 135 when it should be 96. In fact, the likelihood is that both lenses are overstating their true focal length and they are actually both (wild guess) only 80 mm at that focusing distance.

It's important to understand that this is not a fault, and it is also not associated with cheaper lenses. One of the worse cases of this I know is the £1000+ 70-300L, which is only 200 mm at minimum focusing distance.

Additionally. The 55-250 is exceptionally more blurry than the 18-135, which shouldn't be the case at all.

Well, your 18-135 shot is very slightly sharper but there are too many variables to draw any conclusions from this. At another focusing distance or another aperture you might get the opposite result. And in any case the 55-250 shot is plenty sharp enough - sometimes you can look a bit too closely!

treepop
OP treepop Contributing Member • Posts: 723
Re: Is my 55-250 broken?

Thanks for the feedback. I never knew that about focal lengths and zoom lenses!

I know I had mentioned this in my other thread, but thought it was less "18-135 vs 55-250" and more about my 55-250 possibly being faulty.

As for the focus distance affecting clarity, it doesn't seem to help

Thanks for the feedback You guys/gals rock!

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hesbehindyou Senior Member • Posts: 1,834
Re: Is my 55-250 broken?

treepop wrote:

Additionally. The 55-250 is exceptionally more blurry than the 18-135

Centre sharpness looked okay. If you're worried about the corners photograph something both flat and perfectly perpendicular to the camera (brick walls are ace, though seem to have fallen out of fashion) - the blurryness could be due to the camera being at a very slight angle and the aperture being wide open.

treepop
OP treepop Contributing Member • Posts: 723
Re: Is my 55-250 broken?

hesbehindyou wrote:

treepop wrote:

Additionally. The 55-250 is exceptionally more blurry than the 18-135

Centre sharpness looked okay. If you're worried about the corners photograph something both flat and perfectly perpendicular to the camera (brick walls are ace, though seem to have fallen out of fashion) - the blurryness could be due to the camera being at a very slight angle and the aperture being wide open.

Would this affect one lens over the other?

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Hoefie Regular Member • Posts: 279
Re: Is my 55-250 broken?

Excellent explanation ! I didn't know that.
Thanks

Steve Balcombe wrote:

treepop wrote:

I was comparing my 55-250 to my 18-135 and noticed a big problem. 135mm on my 18-135 was equivalent to 96mm on my 55-250.

Already mentioned by the others, but just to give a fuller explanation:

At the simplest level, focusing a lens consists of moving the optics closer to the sensor for distant subjects and further from the sensor for close up subjects. That's why many lenses extend when focusing. However, many others focus by moving internal elements, and this can have a 'zooming' effect, making the focal length shorter (usually) when focusing closer. It's a trade-off - sure we would all prefer to retain the full 'reach' of the lens throughout the zoom range, but internal focusing is generally better for at least three reasons. It keeps the lens more compact in use; it reduces the size and weight of the glass which has to be moved by the focusing mechanism; and it allows for better correction of aberrations at close focusing distances.

The focal length specified in the description of a lens - "55-250 mm" etc. - is always the focal length when focused at infinity. This is also the focal length reported in the EXIF data, and it is not adjusted for focusing distance, so it is often incorrect.

Because the actual focal length shortens when focusing closer, we can say that the 'problem' you see is not that the 55-250 is reporting 96 when it should be 135. It's the opposite - the 18-135 is reporting 135 when it should be 96. In fact, the likelihood is that both lenses are overstating their true focal length and they are actually both (wild guess) only 80 mm at that focusing distance.

It's important to understand that this is not a fault, and it is also not associated with cheaper lenses. One of the worse cases of this I know is the £1000+ 70-300L, which is only 200 mm at minimum focusing distance.

Additionally. The 55-250 is exceptionally more blurry than the 18-135, which shouldn't be the case at all.

Well, your 18-135 shot is very slightly sharper but there are too many variables to draw any conclusions from this. At another focusing distance or another aperture you might get the opposite result. And in any case the 55-250 shot is plenty sharp enough - sometimes you can look a bit too closely!

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treepop
OP treepop Contributing Member • Posts: 723
Re: Is my 55-250 broken?

I just compared my 55-250 to my friends, and it is most definetly softer/out of focus. I used a tripod, the same settings, the same camera and a brick wall (as suggested in this thread). It was quite obvious which lens was the better of the two.

I will be contacting Canon to see if they will adjust it.

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hesbehindyou Senior Member • Posts: 1,834
Re: Is my 55-250 broken?

treepop wrote:

Would this affect one lens over the other?

No, but the depth of field is pretty small at close distances and wide apertures, so small movements of the camera may have a significant effect.

Ron Outdoors Contributing Member • Posts: 826
Re: Is my 55-250 broken?

If you are in the warranty period, Canon will check alignment of the lens and calibrate it for free. I've sent lenses to them and it was well worth the shipping cost to know the lenses are adjusted properly.
--
http://www.ronhartman.net

treepop
OP treepop Contributing Member • Posts: 723
Re: Is my 55-250 broken?

Ron Outdoors wrote:

If you are in the warranty period, Canon will check alignment of the lens and calibrate it for free. I've sent lenses to them and it was well worth the shipping cost to know the lenses are adjusted properly.
--
http://www.ronhartman.net

Aw man. I have to pay for shipping! Not cool man. Not cool.

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