Minolta 300mm F/4 APO

[UY79]

Hi UY...

In some cases, the light might be reflected light and hence the surface where bounce off also result in already a certain amount of aberration. Then this already not perfect edge/surface reflections light gets worsened as the light goes into the lens.

Some lens will have fringing if say taking photos of flourescent light refected on objects in a scene. But in some cases using flash the fringing on the same object is reduced or less obvious.

Is based on my own past experiences....

rgds,
sulhan

So how does "type of aperture where the light comes from (i'm not referring to the aperture of your lens here....)" come into the picture of purple fringing?

 

[sulhan]

So how does "type of aperture where the light comes from (i'm not referring to the aperture of your lens here....)" come into the picture of purple fringing?

Hi UY....

The aperture of reference here is any surface or edge that light actually passes though first before reaching your lens. And the light sourece in reference is the type of light - light can come from back ground as:
- point source (direct)
- Diffused - direct/reflected
- Glowing diffused....

Here is an example of a photo taken with the 80-200mm - this lens gives virtually no CA in 90% of the time. However, here in the example photo, you can see that the CA portion took place on the region where "smoke diffused" light was present. The texture and surface quality of the edges of the pillars which forms the aperture also gives varying fringing characteristics (i.e its not even on the edges).

I have tested side by side Sigma 70-300APO MAcro Super II, Minolta 100-300APO, 70-210f4 and the 70-210 f4.5-5.6. Extent of CA depends greatly on these two factors - source of light + external light aperture.

So i made my conclusion based on my personal tests & experiences.

To conclude - Lens that do not exhibit CA(chromatic aberration )in a type of lighting and aperture condition may not perform similarly in another type of lighting. So unless your image is going to be blown very large - else ......stop bother too much on CA go out and shoot more...:bsmilie: . If have CA - do some correction in PS....

Okay another example.....
(image left) - On board flash
(image center) - Window light
(image right) - Ceiling bounce fill light

Rgds,
sulhan

 

[Zerstorer]

Hi sulhan, those examples that you listed have absolutely nothing to do with CA. These are all prime examples of purple fringing aka sensor blooming which is a phenomenon when fully charged wells in the CCD have a spillover effect affecting adjacent pixels. It occurs on high contrast edges when the exposure nears saturation.

Try shooting directly at any light source and you will almost certainly see this with any lens.

 

[sulhan]

Hi sulhan, those examples that you listed have absolutely nothing to do with CA. These are all prime examples of purple fringing aka sensor blooming which is a phenomenon when fully charged wells in the CCD have a spillover effect affecting adjacent pixels. It occurs on high contrast edges when the exposure nears saturation.

Try shooting directly at any light source and you will almost certainly see this with any lens.

Hiee Zerstorer...

Sensor blooming does not exist inthis manner. They exist in vertical registers and this usually behaves on strong saturated light as you mention. They dont appear purple on only specific edges....

rgds,
sulhan

 

[Drudkh]

Let me share with you guys on the kind of CA I encounter with this lens. Shot was taken at sunset, spot metering.

full image

100% crop

so is this due to blooming of sensor or the CA that the lens did not focus on the different wavelength (RGB)?
The sun was directly in front of me but was covered by clouds.

 

[Zerstorer]

Hiee Zerstorer...

Sensor blooming does not exist inthis manner. They exist in vertical registers and this usually behaves on strong saturated light as you mention. They dont appear purple on only specific edges....

rgds,
sulhan

The same characteristics as you described are exactly whats in your samples.
Btw, only in vertical registers? I don't think so.

CA is typically manifested by a Red/Green/Blue shift and the extent varies with the distance from the edge.

One other type of CA can appear purple, but it only occurs when lenses are shot near wide open.

In my experience, one will encounter the situation u've shown above with almost any lens if shot with similar exposure settings. Back off the exposure and it disappears.

 

[Zerstorer]

Drudkh, what was the difference in exposure between the subject and sky? More than 3 stops?

Just step down the aperture on the lens, if it disappears by f8, it might just be halation if its there irregardless of aperture, its blooming.

 

[sulhan]

Hiee Zers..

The reason why i used that example of the three lighting condition is because for that lens used, it is the best example i can give. As for removing the CCD from the equation, another lens was used and the result as follows. Which means that the lens optics has an influence in the final result...

Here is an image

So the lens do play a part in reducing to a certain level. Yes no doubt that CCD do adds into the equation.......
The 300mm f4 APO is one of the fienst optics out there....again....CA (not specifically purple fringing) can happen at different situations where different lighting condition exisits. Its only how intense or how bad with respect to the image you want than it becomes a concern...

rgds,
sulhan

 

[Zerstorer]

Hiee Zers..

The reason why i used that exam of the three lighting condition is because for that lens used, it is the best example i can give. As for removing the CCD form the equation, another lens was used and the result as follows. Which means that the lens optics has an influence in the final result...

Hereis an image

SO the lens do olay a part in reducing to a certain level. Yes no doubt that CCD do adds into the equation...

rgds,
sulhan

Hi sulhan, with your samples did you shoot then well stopped down at f8 or more?

Also, there appears to be variance in the intensity of the highlights between this and your previous samples. I'd suggest shooting directly at a lightsource instead, since any slight variance in angle for a reflected source changes the intensity dramatically.

Sometimes it is indeed a combination of actual CA AND sensor blooming, so one has to take steps to pinpoint which is the main contributor in different situations.

 

[Drudkh]

Drudkh, what was the difference in exposure between the subject and sky? More than 3 stops?

Just step down the aperture on the lens, if it disappears by f8, it might just be halation if its there irregardless of aperture, its blooming.

yes, its definitely more than 3 stops.

 

[sulhan]

Hi sulhan, with your samples did you shoot then well stopped down at f8 or more?

Also, there appears to be variance in the intensity of the highlights between this and your previous samples. I'd suggest shooting directly at a lightsource instead, since any slight variance in angle for a reflected source changes the intensity dramatically.

Sometimes it is indeed a combination of actual CA AND sensor blooming, so one has to take steps to pinpoint which is the main contributor in different situations.

Hi Zerstorer,

All examples were shot using the same aperture f4. The reason for my posting these example is to discuss how lighting condition can result in different purple fringing behaviour. Many factors in the basket.

rgds,
sulhan

 

[Zerstorer]

All examples were shot using the same aperture f4. The reason for my posting these example is to discuss how lighting condition can result in different purple fringing behaviour. Many factors in the basket.

I would most certainly agree with this. I just didn't agree with your original categorization of it all as being attributed to CA as there are myriad factors involved, some of which perhaps the light was already split and diffracted before it even entered the lens.

I would prefer that CA be used to soley relate to lens issues.

 

[TME]

Zerstorer and Sulhan, u've lost me.... care to post a summary of the arguments? Is sulhan saying that depending on the light source and angle of entry to the lens, CA will be observed for all lenses even the very good ones? And is zerstorer saying that the aberrations we observe need not necessarily be confined only to CA but could include things like blooming(?explain?) and halation(??explain?) or may also be due to spillover effects from adjacent sensor pixels (again u lost me)...

Err.. zerstorer, why does stopping down reduce the apperance of aberrations? And why is it that blooming remains even when stopped down? I think the answer might be related...

Headache.... :sweat:

Thanks!