Help advice needed

Replies to This Discussion

Permalink Reply by nathan mccreery on January 17, 2012 at 12:45pm

It looks to me like you're at the ragged edge of coverage for the lens, which is normal.  I have been extremely disappointed with the lenses manufacturers are putting out.  In film days I would never, ever, expect to see some of what I am seeing in modern lenses, both Canon and Nikon, in the good lenses.

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Permalink Reply by John C on January 17, 2012 at 12:55pm

Thanks nathan! That keeps me off worrying a bit. Is this what you call the chromatic aberration? Is it possible for lenses to deteriorate considering it's a 2yr old lens, just curious i guess :). 

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Permalink Reply by CameraClicker on January 17, 2012 at 1:08pm

EXIF data says 1/25th at f/8 and 12 mm using a Nikon D90.

Canon are re-designing a number of their lenses and bringing them out again as version II.  The reason given is that a sensor needs light to arrive perpendicular to it, even at the edges.  Film could tolerate the light striking obliquely. 

Presumably the Tokina is a DX lens which should have been designed with this in mind....

Did you use a lens hood? 

Was any filter in front of the lens?

If you shoot a plain white piece of paper do you get any colour or dark areas?

Do other scenes exhibit the same problem?

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Permalink Reply by John C on January 17, 2012 at 4:54pm

Hi CameraClicker, thanks for the extra effort to check the EXIF, my fault, I must have mixed up the settings with the other picture..too sleepy :( apologize for that. Thanks for the explanation yes you're right this Tokina lens is a DX format. To reply to your query:

1. Did you use a lens hood?

No. 

2. Was any filter in front of the lens?

Yes, a UV filter.

3. If you shoot a plain white piece of paper do you get any colour or dark areas?

Actually, I tried shooting towards our empty wall it's not white kinda light yellow but close enough.

I shoot one in my bed room and one at the living room. In the bed room the bluish stuff looks evident while at the living room slightly but still bluish. I use hood and without hood to try. In the living room the light is slightly behind my right shoulder and in bed room the light is slightly above my left shoulder. attached shots as reference. all setting are f/8 12mm 1/10. not sure if i can attached all though attached only one in living rm. with no hood. no filter

4. Do other scenes exhibit the same problem?

I saw one shot also having the same issue. the rest it's kinda hard to tell due to the differences in lights.

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Permalink Reply by CameraClicker on January 17, 2012 at 6:41pm

It is not a super scientific test, however, opening the photo of your wall in an editor and then using the eyedropper to sample, through much of the frame R, G & B all report 153.  At the corners, B gets darker resulting in 102.  There is a larger area on the left and upper left that tests with the darker B channel.  That may be caused by the light being to your right.

I would try the same test with another lens to compare the evenness.

Trying something else, I opened the picture in Camera Raw and set white balance near the middle of the frame, then increased exposure until the highlight warning filled most of the frame, that's the big red blob.

As you can see, it is not quite centered.  The left edge is darker than the rest.  If you get a nice centered test result with another lens, I would say this lens is slightly off.  If other lenses give the same result, I would say it may be the sensor that is off, and the new lens brought it to your attention.  Of course if you were casting a shadow or the room light is relatively much closer to the right side of the frame, that would affect the result too.

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Permalink Reply by John C on January 17, 2012 at 8:58pm

Hi CameraClicker, 

Really appreciate your efforts, I'm learning something from your theories :). I decided to redo the shots and compared it using Nikon 16-85mm lens and did exactly what you've done with the Camera Raw settings. I set the camera to 16mm, f8, 1/10s, shots taken at my living room wall same spot. The results were almost the same with the red high lights covering all of the frame or the picture. I've attached here the results with its raw data and camera raw converted. So I guess, from these results can I safely say that both camera and lens are OK?

Thanks again for the help. 

-Regards

Attachments:

• Pictures.rar, 3.6 MB

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Permalink Reply by CameraClicker on January 19, 2012 at 3:19am

When I try to retrieve Pictures.rar, I only get 404 bytes.

If you can get similar looking red and white areas using another lens, then your lens is probably fine, but your light is slightly weak on the left side of the image.

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Permalink Reply by John C on January 19, 2012 at 4:36am

Hi CameraClicker,

i have the files uploaded again hope it works. about the lighting, i will agree with your

observation and i believe you were referring to the picture where you did the camera raw evaluation first. This is probably due to the light source being off-centred and unevenly distributed from behind my shoulder. When I retook the photos, it was morning and the light from the windows are likely giving it a more evenly distribution and thus probably giving a better result. Thanks for looking at it once more.  

Attachments:

• nikon 16-85.gif, 3 KB
• tokina 11-16.JPG, 1.7 MB

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Permalink Reply by CameraClicker on January 19, 2012 at 6:40am

I tried the same steps as last time, using your tokina 11-16.JPG file and got almost exactly the result as I posted previously.

I took a photo of the side of an old Dell computer that was sitting on a table here.  I fired a 430 EX II flash at about 45 degrees up and behind me onto a white stucco ceiling to illuminate the computer.  I increased the exposure in Camera Raw with the highlight warning turned on to give the red blob and stopped moving the slider when most of the frame was red.  This is what I would expect the pattern of a healthy system to look like.

In a perfect world, as the slider is moved, the whole frame would be white at 2.75 and at 2.76 it would all be red, for instance.  For the side of the computer photo, I first noticed red at 2.35 and the setting was 2.75 when I took the screen capture.  If I use Lens Correction in Camera Raw, it brightens the corners, and the image above is the reason it does that.  It can automatically do that for a large number of lenses but unfortunately, Tokina lenses are not on the list.

You should be able to create the same pattern as my camera got, using your Nikon 16-85 mm lens.  You need a flat, evenly lit, evenly reflective surface.  If you can, I would say the Tokina is out of adjustment -- definitely take the test shot without filters.  If the pattern with the Nikon lens is also more red on the right side, it would suggest the camera body needs service.

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Permalink Reply by John C on January 26, 2012 at 6:42am

Hi CameraClicker,

Thanks for your patience. I tried my best to capture as much even light as possible and after so many failed tries :( I finally got one close enough. I have this styrofoam box which I used 2 bright lights to create an even light as much as possible. In summary, the Nikon lens is by far what you would call a "healthy system" based on the results and the Tokina lens is somehow off-centered. Another interesting indicator is the histogram where, Tokina lens is slightly to the right compared with the Nikon lens. 

I guess the question now is:

1. Is this common with 3rd party lenses specifically Tokina for this instance?

2. Is this a big factor in terms of picture quality?

3. Is the Tokina lens damage?

Basically, I have some friends whom have had experienced with 3rd party lenses and most would say that Nikon lenses are the best as expected in terms of Contrast and quality. I just want to get confirmations/feedback. 

I have here attached some files as reference. I'm learning something from your personal experiments :) Thanks a lot. Btw in the attachement movie file, the first 2 sets are from nikon.

Best Regards,

JohnC

Attachments:

• LensCheck.wmv, 448 KB
• tokina 11-16 actual.gif, 95 KB
• nikon 16-85 actual.gif, 111 KB

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Permalink Reply by CameraClicker on January 26, 2012 at 7:20am

In the movie, the spot from 16-85 looks very similar to the spot from 11-16, so it would appear the off center spot you were getting previously was caused by uneven lighting rather than by the Tokina being out of alignment somehow.

The histograms show the Tokina lets in a little more light than your Nikon lens at the same focal length -- assuming the light source and distance from the wall did not change.  The Tokina may like the colour of your wall or the temperature of the light source a little better than Nikon, and let more in.  This is not a big deal.  Your light meter should see the difference if it is enough to matter.

I own several Sigma lenses, which I find are quite good.  I also own several Canon lenses which are very good.  I don't know anything about Tokina, I have never owned one, I am not sure I have even ever held one.

Permalink Reply by John C on January 26, 2012 at 11:35pm

Thanks, to sum up all the discussions and evaluations we did here, the least I can say is that,  it seems like this Tokina lens is still very much OK. =) I wouldn't know that without your help so THANKS guys for the feedbacks and sharing your knowledge/expertise. I'll keep you all posted in case I have a new info about the issue(s) we have discussed here.

 

Best Regards All!

 

-JohnC  

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