Reading mode: Light Dark

Lens starburst at fully open aperture

Go to last post
Atis photo

Atis photo

Member
Messages
36
Reaction score
1
Location
Riga, LV
Hi,

what could be the reason for starburst effect at fully open aperture 0.5'' @ f4 (RF L24-105) ?

0a35e95ee3144a25bd21221bbcd5aaea.jpg

Previously when shooting with EF-M at 30'' @ f5.6 I didn't get that effect. Image below:

d4f18a47b390471e9dacb4eebcbb5aff.jpg

Is it the angle of the light bulb? Or my RF lens is somehow damaged?
 
1Dx4me said:
to get a good starburst, you have to setup your lens down to f16 and lower!
Click to expand...
Hi,

my goal is to get rid of any starburst if possible. And I am wondering why does it appear with fully open aperture?
 
Atis photo said:
1Dx4me said:
to get a good starburst, you have to setup your lens down to f16 and lower!
Click to expand...
Hi,

my goal is to get rid of any starburst if possible. And I am wondering why does it appear with fully open aperture?
Click to expand...
sorry, i misunderstood you, but as has been suggested, i am pretty sure it is the fog that comes in mind. a polarized filter should take care of that, IMO.
 
Atis photo said:
Hi,

what could be the reason for starburst effect at fully open aperture 0.5'' @ f4 (RF L24-105) ?

0a35e95ee3144a25bd21221bbcd5aaea.jpg

Is it the angle of the light bulb? Or my RF lens is somehow damaged?
Click to expand...
I don't have that RF zoom, but other constant aperture zooms I do have achieve their constant aperture by stopping down the iris towards the wider end of the zoom. The nine bladed iris of your zoom would be consistent with the eighteen pointed starburst here.

See the Sunstar section of Ken Rockwell's review here (it's a long way down the review) https://www.kenrockwell.com/canon/eos-r/lenses/24-105mm.htm
 
Last edited:
Sittatunga said:
I don't have that RF zoom, but other constant aperture zooms I do have achieve their constant aperture by stopping down the iris towards the wider end of the zoom.
Click to expand...
WOW, that's a new one for me! That might be the issue! So in reality, at wider end of the zoom, the lens might be brighter than f4, say f3? And it is stopped down to f4 just so that it matches fixed aperture of f4?
 
Well, since fully open aperture is f/4 @105 mm it's diameter is 26.25 mm (or at least apparent diameter). This would make it f/0.9 @ 24 mm.
 
Atis photo said:
Sittatunga said:
I don't have that RF zoom, but other constant aperture zooms I do have achieve their constant aperture by stopping down the iris towards the wider end of the zoom.
Click to expand...
WOW, that's a new one for me! That might be the issue! So in reality, at wider end of the zoom, the lens might be brighter than f4, say f3? And it is stopped down to f4 just so that it matches fixed aperture of f4?
Click to expand...
This lens opens fully at the long end only, indeed. There is no conspiracy here. Take a look here. The off-corner mechanical vignetting is much stronger than what the physical diaphragm does. If you open the aperture somehow more, a large off-center part will get no extra light; you will get a hot spot in the central part only. In other words, the vignetting would be horrible.

And no, it is not a crippled 24/0.95 lens...
 
J A C S said:
Atis photo said:
Sittatunga said:
I don't have that RF zoom, but other constant aperture zooms I do have achieve their constant aperture by stopping down the iris towards the wider end of the zoom.
Click to expand...
WOW, that's a new one for me! That might be the issue! So in reality, at wider end of the zoom, the lens might be brighter than f4, say f3? And it is stopped down to f4 just so that it matches fixed aperture of f4?
Click to expand...
This lens opens fully at the long end only, indeed. There is no conspiracy here. Take a look here. The off-corner mechanical vignetting is much stronger than what the physical diaphragm does. If you open the aperture somehow more, a large off-center part will get no extra light; you will get a hot spot in the central part only. In other words, the vignetting would be horrible.

And no, it is not a crippled 24/0.95 lens...
Click to expand...
Thank you! This answers all my questions! Love the https://www.photonstophotos.net/ and didn't know that they had these cool graphs!

As I shoot mainly night photos and strive to achieve starburst-free photos it is a bit disappointing that L series zoom lens does not provide that. Seems like RF24-105mm f4-7.1 is stm is more suited for me, BUT it is not weather sealed (and probably optically less sharp).
 
Atis photo said:
J A C S said:
Atis photo said:
Sittatunga said:
I don't have that RF zoom, but other constant aperture zooms I do have achieve their constant aperture by stopping down the iris towards the wider end of the zoom.
Click to expand...
WOW, that's a new one for me! That might be the issue! So in reality, at wider end of the zoom, the lens might be brighter than f4, say f3? And it is stopped down to f4 just so that it matches fixed aperture of f4?
Click to expand...
This lens opens fully at the long end only, indeed. There is no conspiracy here. Take a look here. The off-corner mechanical vignetting is much stronger than what the physical diaphragm does. If you open the aperture somehow more, a large off-center part will get no extra light; you will get a hot spot in the central part only. In other words, the vignetting would be horrible.

And no, it is not a crippled 24/0.95 lens...
Click to expand...
Thank you! This answers all my questions! Love the https://www.photonstophotos.net/ and didn't know that they had these cool graphs!

As I shoot mainly night photos and strive to achieve starburst-free photos it is a bit disappointing that L series zoom lens does not provide that. Seems like RF24-105mm f4-7.1 is stm is more suited for me, BUT it is not weather sealed (and probably optically less sharp).
Click to expand...
No constant aperture zoom of any quality will provide that at anything other than the long end of the zoom. The STM lens might, and you can probably arrange the composition so that the dodgy corners are black anyway. Night scenes generally look horrible if it's raining or dusty anyway.
 
Sittatunga said:
Night scenes generally look horrible if it's raining or dusty anyway.
Click to expand...
I will disagree on that :) I love to go outside when it is raining or foggy, creates perfect mood, so weather sealing is a must. I switched from M50 for that reason - so I don't have to worry about weather. Will have to search for options maybe from other brands..
 
You must log in or register to reply here.

Keyboard shortcuts

f
Forum
m
My threads
Mobile site
About
Editorial content
Cameras & Lenses
Community
All content, design, and layout are Copyright © 1998–2025 Digital Photography Review All Rights Reserved.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
When you use DPReview links to buy products, the site may earn a commission.
©GPS Media - Guides, Products, Services.
Back
Top