Sony 18 - 250mm vignetting - what do you think

[mic291]

Hey everyone

I am sure a few people will suggest the solution is Cannon or Nikon, but stick with me for a moment.

For a while now I have been using a Sony a100 DSLR with a newly released 18-250mm lens which was actually released when the new A700 came available several months back. On a trip to the US I upgraded to the A700 and I was taking a few shots the other weekend, playing around and I saw some vignetting which I have never seen before.

Looking at a few of the fotos, most issues are at f4 but a few are noticeable at f5.6.

The strange thing is I was using this lens for about 3 months on an a100 and I do not recall seeing this at all which has been worrying me that its related to the A700. If this is the lens, and is normal then thats a very bad lens in my opinion and when I am in HK next week I will purchase a Sigma 50-150 f2.8 or something similar.

Here is an example of the test shots at f4
http://www.flickr.com/photos/mic291/2363713936

Here is an example at F5.6
http://www.flickr.com/photos/mic291/2362883465

As mentioned, I dont think I ever saw this when using the A100.

What do you think? Dodgy lens quality or a mechanical problem with the lens itself?

Cheers
Mike

[sirhc55]

Hi Mike

A couple of questions, are you using a lens hood? What focal length were these shot at? Were you using a polariser?

In pic #2 if you look at the bottom right hand corner there appears to be no vignetting! The sky coloration looks very much like the effect you get with a polariser.

[photohiker]

Given the extreme range of this lens, I don't think the vignetting is horrific.

What do you use for PP? LR and PS and others can easily correct vignetting, have you tried it?

I'd be surprised if it was the filter or lens hood, the sample photos are not taken fully wide. What does it look like at 18mm? Have you tried it without hood or filter?

Michael

[mic291]

Sorry Chris, I should have added that info !!

No lens hood or polarizer and the focal length is about 28mm. Thats the thing that suprised me as I would have not been too suprised had it happened at 250mm.

As mentioned I have not seen this before on the a100 and maybe took about 100 fotos for a photography course and never saw the vignetting. with my f1.4 50mm prime on the a700 the fotos do not have the issue.

WIll keep playing !!

Mike

[mic291]

Interesting...

Thought I would post to see what you all may think as I dont have that much experience which such an extreme lens...

On a Sony forum where I posted the question some of the feedback from the site admin that seems to have some relation to Sony included the following:

Response 1: The simplest would be that you have a filter which interferes with the peripheral image, unlikely or you would have mentioned it.
- As mentioned from me, no filters etc.

Response 2: The second is that the lens has in some way become misaligned but this should affect sharpness.
- This is one concern that I have

Response 3: The third is that the vignette mapping of your A700 sensor, a built-in function required for all lenses, is not correctly encoded while your A100 was OK. This is possible, but it would show in the form of increased vignetting with all lenses.
- This is along the lines of what I am really worried about


Is the example I have shown very bad as this same person stated, "It could also be that the combination of conditions, contrast and exposure made these effects very visible. I certainly have had similar results on film from the 28-300mm Tamron XR, and the 18-200/18-250 models do show strong vignetting - as do all lenses like this. But not as bad as your example."

Regards
Mike

[gstark]

In pic #2 if you look at the bottom right hand corner there appears to be no vignetting!

Chris,

Do you think that might be because of the proximity of the sun to that corner within this image? I think that it may have a mitigating effect and thus is negating the apparent vignetting.


Mike,

Is there a difference between the rated crop factors of these two bodies? While they may be nominally similar, if there's an actual/real difference, that might account for this.

Are you able to shoot the same image with each of the bodies? That would give us a valid basis for comparison between the two bodies, as well as a reference point from which to make a real judgment. I'm not sure that there's much that can be construed from just looking at this pair of images, except to accept the fact that yes, there is some vignetting present. Once we can compare the results with those obtained from another body, we can then start to infer that the lens, or one of the bodies, might be causing some issues.

[mic291]

Hi Greg

As of last weekend I unfortnately no I do not have the a100 to further evaluate with that body.

So the plan is to take a number of different fotos at varying focal lengths and aperture and then use the 50mm lens however thats not a great test. What I am trying to see if I can locate a standard 18-70mm lens and try the same type of fotos.

Thanks
Mike

[gstark]

Greg??

Mike,

What about a very simple test then: stick a piece of white paper onto a wall or a fence. Basically, you're going to do a variation on a focus test, except that you won't be using a focus test chart. Do this with good, even lighting across the target.

Put the camera on a good tripod, set the exposure to manual, and get a good exposure reading. Incident if you have a handheld meter, otherwise remember that your camera's meter is going to try to compensate its reading to a grey, so you'll need to adjust the reading to compensate.

Fill the frame with your white paper at various focal lengths, and then shoot at varying exposure settings, but using the same EV. IOW, get your EV and set the lens at wide open with the matching shutter speed. As you stop your lens down, alter the shutter speed accordingly to keep that EV, and reshoot. Repeat through the range of apertures available at the same focal length.

Then repeat at different focal lengths.

While that won't give us any comparative data vs another body, it at least will give you a set of controlled results that you can compare, one against the other.

[ATJ]

No lens hood or polarizer and the focal length is about 28mm. Thats the thing that suprised me as I would have not been too suprised had it happened at 250mm.

I would have thought that vignetting would be more common at wide angle than at telephoto. When the angle of vew is wider your more likely to get light blocked by things (lens hoods, filters, the lens itself.

[photohiker]

Me too. Any zoom lens I have seen with vignetting has been worse at it's widest than at it's longest.

Unless it's a faulty copy of the lens, I still think it's a bit of a non-issue these days, it's very easy to correct in Lightroom.

Michael

[mic291]

Hi everyone

Just finished my testing with interesting results.

The tests using 2 A3 pieces of white paper on the wall:
- I tested at 28mm, 50mm, 100mm and 200mm focal lengths
- EV as 0 for every test
- Adjusted f-stop from lowest, f/3.5 - f/20

Results:
- vignetting reproduced in every focal length, however its typically worst from 28mm -100mm but still noticeably bad to full focal length.
- vignetting is very bad from f/3.5 through to f/10 where once past f/10 it starts to become quite acceptable

Testing with my 50mm f/1.4 prime, regardless of f-stop is sharp and has absolutely no vignetting at all. Regardless of what I try, there is absolutely no vignetting.

The confusing part:

- I have been through 25+ fotos that were taken with the A100 and the 18-250mm lens and regardless of what f-stop or focal length, I simply cannot see any vignetting at all.
- the sensor on the A100 and A700 is essentially the same size, however the older a100 is CCD and the new A700 has the new Bionz which will be in the A900 full frame

This must be an issue with this lens on the A700 which has a very different sensor, however my logic is that given they are the same size sensor, there must be some sensitivety or vignetting compensation on the a700 that is not happy with this lens.

The only thing I can do now is test with another variable length lens, if I can find one before I purchase the 50-150mm 2.8 Sigma.

....should got a D300 for less hassle I guess

[mic291]

Well, seems as though I have a conclusion to this saga, still not sure, but a conclusion I thought I would share !!

Yesterday I spent time at Teds and the great guys there let me test with the Sony 16-105mm lens and kit 18-70mm lens and I spent more time with the 50mm f/1.4. Testing with my 50mm f/1.4 prime, regardless of f-stop is sharp and has absolutely no vignetting at all. Regardless of what I try, there is absolutely no vignetting and the fotos are as expected - http://www.flickr.com/photos/mic291/2373714196/

With the kit lens 18-70mm and 16-105mm vignetting is still noticeable on the 16-105mm however it is minor at wide angle with no vignetting above f7 http://www.flickr.com/photos/mic291/2373714282/ and on the 18-70mm there was still some vignetting at wide angle at f/4 http://www.flickr.com/photos/mic291/2373714412/

So today I spent time at Progear Australia, an authorised Sony Repair Centre and the team there would have to be the most professional consumer support organisation I have ever dealt with.

First things first, they were adamant that this is in no way the camera. Any issue with vignetting they have seen on the Alpha series or other cameras they have dealt with where the body is at fault never displays with vignetting on all four corners, its typically one corner only.

They took my camera for an hour and ran a series of tests, they used multiple lenses on my A700 and they used the 18-250mm lens on multiple bodies.

Summary:

- The 18-250mm lens vignetting happened on every body they tested which includes other non A700 bodies
- Worst vignetting was at 30mm focal length under f/10 which was suprising
- Other "kit" lenses had some level of vignetting, however all within acceptable manufacturer tolerances

Even though they cant explain why I never saw it on my A100, they are sure its not my A700 and confirmed its working perfect. The A700 with the new CMOS sensor also is very sensitive with lenses with an aperture above 5.3 and is suited (isnt every camera) to 2.8 or lower apertures.

What they did was carry out tests as per Sony specifications and sent them to Japan as they were shocked at the performance of the lens which they also dont think its faulty.

They did all of this for free !! Great bunch of people !!

Mike

[gstark]

What they did was carry out tests as per Sony specifications and sent them to Japan as they were shocked at the performance of the lens which they also dont think its faulty.

So, what, exactly, is the resolution from your point of view? Did anyone test other examples of the same lens to see if this was typical performance?

And if the lens is not regarded as faulty, but does perform so poorly, what does it take to have a lens regarded as being faulty?

I hope I'm not sounding overly critical; I'm just curious abut this.

Thanx.

[mic291]

Hi Gary

Its not critical at all, its the same question I am still asking myself. I am also in the back of my mind questioning the body......but thats the engineering side of me !!

I tested a Tamron 18-250mm yesterday also, Tamron make the Sony lens by the way, and I found the same issue so yes we have tested other examples of the lens. What I could not test was the Tamron on a different A700.

So the resolution at this stage is everyone claims there is no way its the camera and its more a case of buyer beware. Or more specifically the learning is that I was an idiot for paying so much for a Sony badged Tamron lens, i.e. the Sony version cost double when I could have purchased the Sigma 50-150mm 2.8 lens for less money. eBay for that lens and when I get to Hong Kong on Sunday, a shopping I will go !

I will go into a Sony store this weekend though and test their A700 with the 18-250mm and see what happens. If there is vignetting then I will be comfortable that its the lens.

Mike