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A little minor problem with the 28-70.. LIttle it may be, its enough to bother me... Problem could potentially be setting and error on my behalf, I know ---- but I'll give you guys a run down on what I've tried to attemp fixing it, but to no avail.

Equipment used
- D200
- SB800
- SB800 diffuser

Settings
- Normal - no sharpening, softening, vivid etc etc...
- direct flash no bounce using the sb800 diffusion attachement. still occurs even without the attachement.
- White Balance set to Auto
- 1/60 shutterspeed
- shot at 70mm
- f2.8 - also happens @ f3.2, f4, f5.6
- distance to subject - about 1.5 meters


This is an image shot at JPG Low Quality / Basic then resized to put up on the net. Doesnt really matter what quality i shoot - i can easily replicate the same potential problem in High Quality..




This is an image zoomed into the problem area.



Do you guys notice the purply glow on the end caps...
I cant seem to replicate this problem with my other lenses - and if it does happen its very very very slight not even worth worying about.

Checked the settings in the camera and there is no custom setting that i can find that may cause this.

1. I also tried it on my second body and it does exactly the same thing.
2. I thought it may have been my filter on the lense - but not the problem
3. I tried a second flash thinking it might be the flash and again the same result...
4. Tried changing the white balance to "Flash" - no luck either.

I'm a little stomped with this one ...

This bothers me as I took some pictures of a couple today that showed this same "potential problem" on their eyes, instead of the catch light being white it has a purple ring around the light..



?????

Is this a problem with the lense - i may need to check out someone elses 28-70 to do the same tests --> maybe "RAY" i might have to come and visit you again...

during testing - the only way i got rid of the purple glow on the endcap is when shooting at f11 ???

I need a PURLE-EYE reduction feature ????

Care to comment guys ???

Thanks.....

That is strange, I've shot too many with this lens on the D70 and D2H, had no problem at all with the flash at f/2.8 or anywhere.

Does it happen with other lenses? How about RAW?

If your lens is still new, maybe a trip to the repair station will tell what exactly is going on...

Looks like (lateral) chromatic abberation aka purple fringing. It's an optical charactersitc of apparently even the best pro grade Nikkors.

Usually happens at high contrast edges, typically more apparent with wide angle lenses - but it seems in this case like the white of the flash hitting the edge of the black lenscap was enough to bring it out.

Stopping down the lens will minimise/eliminate it. As will correct focusing. (ie. lenses or users who don't focus correctly will exacerbate the purple fringing).

I do personally find it offensive - CA and with lenses that produce bad bokeh. Hence my most often used lenses are ones that don't seem to produce CA as badly

There are software fixes available for CA, Capture and I think Photoshop also has 1 button all purpose solution, or via manual fine tuning...

I have noticed it on the 35/2, 80-200/2.8 wide open, 135/2.8 and to a lesser degree the 18-70 towards the wide end of zoom. The Defocus Control lenses, 105 and 135, were specially made not to correct for this kind of abberation, hence will exhibit this noticeably, and from my limited experience with the 105DC, it does.

It's not a problem with the lens. It comes down to the physics level - digital sensors favouring incoming light that's exactly perpendicular, and light hitting the sensor from slight angles due to the refractive properties of the lens' elements, causing the shorter wavelength (ie. purple/violet end of the spectrum) to bend a little bit further than the other colours that make up white light.

The 28-70 was designed in the days of film, so I would hypothesise that none of this was a consideration in its day. Since it's difficult and costly to change its optical formular, the lenses of the same model built today would have the same 20 yr old optics and also the lack of optimisation for digital use.

Newer lens designs, made since the intro of the digital sensor, would feature aspheric elements, specialised optical coatings and other applied Nikon expertise in reducing/correcting for these (and other) forms of optical abberations.

Oh yes, needless to say, take off any unnecessary filters (all UV and skylight are unnecessary AFAIC) as they won't help.

Using the same camera & flash --> I couldnt replicate the same results with my 80-200 --> 80mm right up to 200mm @ f2.8 Not with my 50mm either. Not with the 12-24 or the 18-70 either - though these are DX lenses, so if its to do with the older style lens then that may explain this.

But what about the above non DX lenses..

I migt have to try it with my 10year old 35-70 f2.8 to see if it has any effect.

Will need to do more thorough testing. N yes it is a brand-spankin-new lens - I've sent an email to the seller too just to enquire if they've had soemthing similar occur previously - i've mentioned that I will further more do testing prior to pursuing warranty...

I will need to compare it againts another 28-70 to make any conclusion.

I dont want to shoot an entire event with everyones eyes having this purple glow. Its as bad as "red eye"...

thanks guys...

What if you relocate the flash so that it's off-camera?

As Chi has pointed out, this occurs at high contrast edges .... basically it's happening when parts of your image are beyond the specifications for that the camera is rated to handle.

Can you shoot the same subjects/conditions using a different camera? A different version of the same lens? Maybe also using film?

gstark wrote:What if you relocate the flash so that it's off-camera?

As Chi has pointed out, this occurs at high contrast edges .... basically it's happening when parts of your image are beyond the specifications for that the camera is rated to handle.

Can you shoot the same subjects/conditions using a different camera? A different version of the same lens? Maybe also using film?

Relocating the flash could potentially fix it but the type of photography i do would need the flash mounted on the camera. Will still try this though.

I have tried using a different camera, same model shooting the same condition with the same result.

I think i should try a different model, like a D2_, D80 or D70...

I will try and organise to shoot with a different version of the same lens.

No i havent tried film - might be worth the excercise - though I would really like to nut it down in the digital world as am planning to only shoot digital in the near future...

thanks..

blackD200 wrote:Relocating the flash could potentially fix it but the type of photography i do would need the flash mounted on the camera. Will still try this though.

Why ??

What type of photography that needs this?

I can accept that it's a convenient location, and that it's an easy location for the flash head within and from which you can easily work ... but need ????

I'm thinking in terms of a bigger diffuser and/or even a slight relocation of your flash and lens relative axes to help alleviate what you're seeing.

A larger diffuser may help reduce the hotspots, which I believe are, ultimately the root cause of this issue. Remove the hotspots, and the problem is gone.

Change the relative angles/axes, and you then alter the paths for the reflections of the hotspots.

gstark wrote:

blackD200 wrote:Relocating the flash could potentially fix it but the type of photography i do would need the flash mounted on the camera. Will still try this though.

Why ??

What type of photography that needs this?

I can accept that it's a convenient location, and that it's an easy location for the flash head within and from which you can easily work ... but need ????

ok fair enough... no so much of a need but yes definetely a very convinient location.
Been shooting mostly events so am always on the go and not much time to setup flash, and the most convinient way of lugging a flash for me is monted on the camera shoe

maybe i need( may want to try ) a setup similar to my old hammer Metz CLT45 where it is mounted on the side, though i think this may still be an issue with portrait oriented shots.

gstark wrote:Change the relative angles/axes, and you then alter the paths for the reflections of the hotspots.

will be trying some of this too...

thanks for the great feedbacks...

Look! No further need to worry:

as Chi mentions, it's lateral CA. Good Link Here

I haven't had too many problems at all with the 28-70 experiencing CA, but it can happen.

I've always found that CA and flare most commonly affects super wide angle lenses, or those with a lot of glass (fast). The 28-70 is sort of wide-ish (in its native film environment, and it's got a lot of glass!)

Of the 458 shots from the ferry hop, about 300 were taken with the 28-70. Of that, 3 images (3 F ev bracket) show noticeable or offensive CA.

It took a fair bit to provoke it though. The positioning of the light source is hardly going to deliver the best from the optics. Tthis image has both veiling glare (flare on ferry) and lateral chromatic aberration on the contrast edges of the water sparkle.


(Note: this ain't in the critique or comment forum - i know it's not a great image! )

I think I shall ask tho, were there any filter on top of the lens when you took those photos??

did similar tests with my 10year old 35-70 f2.8 last night and it came out perfect.. no CA at all - open wide at f2.8 70mm and 35mm Shot some direct flash into someones face and the catch light was white-ish... no purple glow..

At the same setting i plugged in the 28-70 f2.8 and shot at 70mm as well and purple glow around the catch light.
...its terrible compared to an old lens for what i'm testing...



Even just using the flash for fill on outdoor portraits, I still get the CA on the catchlight. Is this a 28-70 feature ??? I will def need to test another 28-70 for comparisson.

I shoot bounce as much as I can, but for the times I cant - this could potentially mean extra time in PP fixing them up... maybe I'm just being really picky, I dont mind it too much if its on an object, but i just dont like the CA on someones eyes.

I can finally put this to bed.

I shot with a D80 + 28-70 + flash w/ diffuser the other day showing the samme result. At any focal range it produced the same results when shot at wide open - right up to f7. This eliminated the D200 in the equation.

So i was very inclined that it was the lens.

So today ( thanks to Ray ), i got to use a fellow members 28-70 to do the same test.. To my surprise it showed the same results. I was actually more releived than anything. I thought I may have purchased a lemon. Now I can rest my mind... and stop searching in google for "Chromatic Abberation Nikon 28-70 f2.8" - must have gone through pages and pages of google results trying to find someone in the same scenario.

But a lemon its not... Its a feature of the lens i'll very easily learn to live with, and I think to most people prob isnt even an issue. I think i was just a little picky

Thanks everyone for the great info and feedbacks.