This Month Through Your Adapted Lens -- January 2020 -- Part 1

[M_digicapt]

Hmm, swirly bokeh from a modern Canon lens?? That's something new!

Swirly bokeh is typically the result of vignetting. The Canon EF-S 55-250 f/4-5.6 IS STM at 250 mm and f/5.6 has about 1 stop of vignetting in the corners of Canon APS-C (1.6 crop), and it's going to be even stronger in the corners of Sony APS-C (1.5 crop). So, in retrospect, it's not that surprising.

All lenses have compromises. Here, it looks like high vignetting is the price one pays for other qualities such as lightness (375 g), IS, and internal AF, which tend to favor physically smaller elements.

If you want to avoid this, an EF lens such as the 70-200/4L IS USM or 70-300/4-5.6 IS USM might be a better option.

Regards,

Alan

I think the IQ is very good and the swirly like bokeh kind of cool actually. Vignetting for me is usually not a problem because I tend to crop them anyway.

Do the wide angle and standard zooms also vignette?

 

[aidaho]

--
I like to shoot with manual lenses. Here are some of my photos: https://www.flickr.com/photos/curry-hexagon/

 

[Photodog2]

Very nice again.

 

[Photodog2]

Has that film noir look. Nice.

 

[Photodog2]

Beautiful architecture and your photos display them nicely.

 

[Photodog2]

Nice colors. I don't know what some people are talking about when they say Sony doesn't have good colors.

 

[Photodog2]

Excellent product photography. Beautiful product and the lens used performed well.

 

[biggles266]

Hmm, swirly bokeh from a modern Canon lens?? That's something new!

Swirly bokeh is typically the result of vignetting.

That's something I've never heard before in all the years of camera reading I have done, and to be honest, doesn't sound right to me. Do you have a link that explains this?

 

[Alan WF]

Hmm, swirly bokeh from a modern Canon lens?? That's something new!

Swirly bokeh is typically the result of vignetting.

That's something I've never heard before in all the years of camera reading I have done, and to be honest, doesn't sound right to me. Do you have a link that explains this?

No, I don't have a link.

However, see the image below, taken with the same 55-250/4-5.6 IS STM on the same a6000. I manually focused to about 5 meters. The lights are much more distant. You can clearly see the vignetting of the pupil in the out-of-focus images of the lights, and see that the bokeh is tangentially elongated away from the center. I think this is what causes swirly bokeh.

People say it's combination of vignetting and field curvature. Now, I can understand how field curvature helps to throw the periphery further out of focus, but I can't see how on its own it gives swirly bokeh. I could well be wrong, but I think the crucial ingredient is vignetting.

Regards,

Alan

 

[Alan WF]

Do the wide angle and standard zooms also vignette?

The 10-18/4.5-5.6 IS STM is notorious for vignetting. Wide open, it has about 2.2 stops of vignetting in the corners at 10 mm and about 1.2 stop at 18 mm.

The usual nicer standard zoom is the 18-55/3.5-5.6 IS STM. Wide open, it again has about 1.8 stops of vignetting at 18 mm, dropping to about 0.7 stops at 55 mm. I have the /4-5.6 version, and it is more compact, so possibly has more vignetting.

Regards,

Alan

 

[M_digicapt]

Do the wide angle and standard zooms also vignette?

The 10-18/4.5-5.6 IS STM is notorious for vignetting. Wide open, it has about 2.2 stops of vignetting in the corners at 10 mm and about 1.2 stop at 18 mm.

The usual nicer standard zoom is the 18-55/3.5-5.6 IS STM. Wide open, it again has about 1.8 stops of vignetting at 18 mm, dropping to about 0.7 stops at 55 mm. I have the /4-5.6 version, and it is more compact, so possibly has more vignetting.

Regards,

Alan

Thanks.

With M43 probably little vignetting, though?

 

[biggles266]

Hmm, swirly bokeh from a modern Canon lens?? That's something new!

Swirly bokeh is typically the result of vignetting.

That's something I've never heard before in all the years of camera reading I have done, and to be honest, doesn't sound right to me. Do you have a link that explains this?

No, I don't have a link.

However, see the image below, taken with the same 55-250/4-5.6 IS STM on the same a6000. I manually focused to about 5 meters. The lights are much more distant. You can clearly see the vignetting of the pupil in the out-of-focus images of the lights, and see that the bokeh is tangentially elongated away from the center. I think this is what causes swirly bokeh.

People say it's combination of vignetting and field curvature. Now, I can understand how field curvature helps to throw the periphery further out of focus, but I can't see how on its own it gives swirly bokeh. I could well be wrong, but I think the crucial ingredient is vignetting.

Regards,

Alan

I think I see what you are saying but it still doesn't seem believable. If a camera has software correction turned on (like Canon's Illumination correction or whatever it's called), then vignetting is corrected in camera, and the user doesn't see it. Are you saying if the camera removes the vignetting it will or won't still give the swirly bokeh? And similarly if you remove the vignetting in post by doing a reverse vignette slider bar, then there is no vignetting, but the swirly-ness will still be there, right?

Since very many lenses have vignetting wide open, but only a very few are famous and known for their swirly bokeh, it doesn't seem logical to me that vignetting causes it.

 

[fferreres]

Do the wide angle and standard zooms also vignette?

The 10-18/4.5-5.6 IS STM is notorious for vignetting. Wide open, it has about 2.2 stops of vignetting in the corners at 10 mm and about 1.2 stop at 18 mm.

The usual nicer standard zoom is the 18-55/3.5-5.6 IS STM. Wide open, it again has about 1.8 stops of vignetting at 18 mm, dropping to about 0.7 stops at 55 mm. I have the /4-5.6 version, and it is more compact, so possibly has more vignetting.

Regards,

Alan

Thanks.

With M43 probably little vignetting, though?

It is thought sometimes that vignetting is a defect, but it’s a design tool usually the vignetting makes the outer high angle rays not pass through the aperture. In other words, it masks out the most aberrantes worst performing part of the lens. If you could have the same design and to not vignette, it’s be a much softer image. You se clearly the vignetting has this oval shape in OOF areas, indicating which part of the front element becomes black at top apertures.

Vignetting is not at all bad, as it could not happen the extra light would be all aberrated

 

[aidaho]

I think I see what you are saying but it still doesn't seem believable. If a camera has software correction turned on (like Canon's Illumination correction or whatever it's called), then vignetting is corrected in camera, and the user doesn't see it. Are you saying if the camera removes the vignetting it will or won't still give the swirly bokeh? And similarly if you remove the vignetting in post by doing a reverse vignette slider bar, then there is no vignetting, but the swirly-ness will still be there, right?

Since very many lenses have vignetting wide open, but only a very few are famous and known for their swirly bokeh, it doesn't seem logical to me that vignetting causes it.

Alan and Alex talk about mechanical vignetting, not optical.

To my eye strong mechanical vignetting is a pre-requisite but not the whole story. Not all lenses with strong mechanical vignetting cause swirl effect for me.

And on the few occasions I've managed to induce subtle swirl in lenses not known for exhibiting one. I believe spherical aberration correction at the given focus distance and aperture also plays it's part.

 

[Daneland]

Thank you for your kind words...

 

[Alan WF]

With M43 probably little vignetting, though?

Less. Ken Rockwell often publishes vignetting images in his reviews:

• 10-18/4.5-5.6 IS STM
• 18-55/3.5-5.6 IS STM
• 55-250/4-5.6 IS STM

You can evaluate these for yourself.

Regards,

Alan

 

[M_digicapt]

With M43 probably little vignetting, though?

Less. Ken Rockwell often publishes vignetting images in his reviews:

• 10-18/4.5-5.6 IS STM
• 18-55/3.5-5.6 IS STM
• 55-250/4-5.6 IS STM

You can evaluate these for yourself.

Regards,

Alan

Thanks

 

[Alan WF]

If a camera has software correction turned on (like Canon's Illumination correction or whatever it's called), then vignetting is corrected in camera, and the user doesn't see it. Are you saying if the camera removes the vignetting it will or won't still give the swirly bokeh? And similarly if you remove the vignetting in post by doing a reverse vignette slider bar, then there is no vignetting, but the swirly-ness will still be there, right?

Vignetting typically means that as the field angle increases, less light reaches the sensor. This makes the image darker away from the field center. This darkening can be corrected by simply artificially increasing the brightness of the electronic image.

However, let's think a little more deeply. Why does vignetting cause less light to reach the sensor? Because something blocks light from passing through the nominal pupil, which is normally at the position of the iris. Consider two parallel metal plates each with a circular hole. The plates are separated somewhat and the centers of the holes are aligned. One of the holes represents the nominal pupil and the other a vignetting element, perhaps an undersized optical element or a lens hood. Consider viewing the holes from a position on the axis defined by their centers. The image of the pupil will be circular. Now move your viewing position off axis. Eventually, the edges of the two circles will touch, and after this the pupil will no longer be circular, but will be defined by two arcs of the circles and will be elongated. The elongation will be tangential. This can be seen clearly in out-of-focus images, like the one I showed.

The illumination correction will not correct the shape of the pupil. It will not make the pupil circular again. Even with illumination corrections, the out-of-focus highlights will still be extended tangentially.

Tangential extension of the out-of-focus image is precisely swirly bokeh.

Since very many lenses have vignetting wide open, but only a very few are famous and known for their swirly bokeh, it doesn't seem logical to me that vignetting causes it.

You need strong vignetting to give noticeable tangential extension (I'd say at least one stop) and a situation that favor an out-of-focus background (so faster apertures and, especially, longer focal lengths).

I'll see if I can create a swirly lens with by artificially adding vignetting to a non-swirly lens. It might take me a few days to find time to do this.

Regards,

Alan

 

[shuttlexman]

Beautiful architecture and your photos display them nicely.

Thank you!

 

[shuttlexman]

Nice colors. I don't know what some people are talking about when they say Sony doesn't have good colors.

I agree completely. I'm sure it's a problem with their workflow or lack of calibration of their displays. Maybe it's the Canon lens adding its own persona to the finished photos. I always shoot RAW and use a calibrated monitor and know my post processing software well. Been shooting RAW since my Canon 10D days way back in 2004/2005.