Sigma 150-600 - Bad copy?

A friend just purchased this lens and sent me a picture, asking if something was wrong with the lens. She did have a CP filter on the front, and I've asked for a test image without the CP filter and haven't received it yet. However, I've never seen anything quite like this and am wondering if any of you have seen anything like this and know what it might be. Thanks.

That is quite weird. More images might help, definitely without any filters.

I'm guessing the filter may have been a contributor. It also looks like the plane of focus was in front of the flower, based on the below and to either side of the flower being a bit sharper (but not all that great) and looking like they are in front of the flower.

I wonder was there a window in the image path as well?

Just to be clear, we are talking about these, right?

While I have no idea, I notice around the plane of focus, they seem focused, in the foreground they are much smaller, in the background they appear doubled, or ghosted. I think that will be a clue in identifying the problem.

The general doubling (ghosting) of the oddities suggests reflections between the filter and the front element. The straight-line doubling just below and to the left of the upper left set of oddities looks like the internal edge of a double-pane window.

EDIT:
On closer examination, it looks like a window glass reflection. That is my guess. Here is the crop.

I got very similar images when I put an a cheap CPL filter that came with the lens when I bought it.

sdipirro wrote in post #18052320
A friend just purchased this lens and sent me a picture, asking if something was wrong with the lens. She did have a CP filter on the front, and I've asked for a test image without the CP filter and haven't received it yet. However, I've never seen anything quite like this and am wondering if any of you have seen anything like this and know what it might be. Thanks.

I would expect it is the filter. Most long telephotos do not play nice with filters. Also, large 95mm filters are very expensive for good ones, and even those ones cause issues on long lenses like this. A cheap 95mm filter would be a nightmare for quality.

Very best,

You guys are right on the money. I finally got a bunch of images from her without the CP filter, and they look fine. I had never even heard of the brand of this CP filter, but it's obviously the problem. Thanks very much!

I just went through this same issue when I purchased my Sigma 150-600mm C lens.

I picked up a cheaper CPL and when I first tried the lens it was sharp side to side on my 70D MKII but when I put the CPL on it and took some pictures it gave the same effect with a slight blurring on some parts of the image and somewhat sharp in others with a poor overall IQ.

I've sent the filter back and I'm hesitant in getting another even at a higher cost.

I will probably look at some ND filters and not an adjustable one to see how that works for longer exposure.

I'm somewhat disappointed and reluctant to get another somewhat more expensive CPL as I like the function on water shots and I'm looking to use the lens for surfing shots.

I stopped using UV filters years ago when I took pictures of a JROTC event my son was part of with hanging lights produced doubling ghosting of the lights in the images.

Overall I'm very impressed by the copy of the lens I got and feel it produces pictures that are on par with my 70-300mm L lens.

I have been very happy with my 150-600C. Since I shoot airshows, in manual exposure mode, a CPL filter is not particularly helpful. Here in the UK you don't see too many filters advertised in sizes over 82mm. The store where I got my 150-600C only offers one 95mm CPL and that costs £159, it's a Sigma one, I guess that would be around $180 once you allow for taxes and currency exchanges. If I were to get a CPL or even an ND filter for the lens I would go for a Sigma one from choice, but WEX don't have one listed.

Alan

I think I remember paying over $200AUD for the Sigma 105mm CPL back when I got my 120-300 a few years ago. Might have even been close to 300.

It doesn't spend a lot of time on the lens but when I do use it I can't say I notice any IQ degradation (most likely happening to some degree but I'm not noticing it)