Forgot Password
Pentax Camera Forums Home
 
Log in or register to remove ads.

Showing results 1 to 6 of 6 Search:
Forum: Troubleshooting and Beginner Help 05-23-2018, 08:16 AM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
Got the E-mail about that - I can't say i'm happy about it either.
Forum: Troubleshooting and Beginner Help 05-18-2018, 01:44 AM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
It isn't at all improbable that condensation formed inside the lens somewhere, and managed to pick up some grease/dust and when it dried up, left a deposit upon the surface of a lens element somewhere in the rear cell of the lens.
Forum: Troubleshooting and Beginner Help 05-17-2018, 05:05 AM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
Does the blob show up the same size no matter what focal length you are using? or does it vary?




That's because what you have shown us is flare, non-image forming light. The blob you have depicted is smaller than this, and would be hidden in the shadows of this overexposed image.
Forum: Troubleshooting and Beginner Help 05-17-2018, 05:05 AM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
Does the blob show up the same size no matter what focal length you are using? or does it vary?




That's because what you have shown us is flare, non-image forming light. The blob you have depicted is smaller than this, and would be hidden in the shadows of this overexposed image.
Forum: Troubleshooting and Beginner Help 05-16-2018, 10:44 PM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
No, it doesn't. However, I would get the lens checked - of only to remedy the issues when it is zoomed to 50mm.


One could argue this is largely semantics, but If a lens is projecting an image with such inhomogenities in its illumination pattern, there is clearly something rotten in the state of denmark. Retrofocus wide angle lenses at their widest focal length can extend inside the mirror box of an APS-C camera to the point where small spots on the sensor can become visually more apparent than they ordinarily would be. The Sigma 8-16mm f/4.5-5.6 is a lens that Is annoyingly good at highlighting this.



Is the position of the spot consistent? does is appear under controllable conditions? Have you tried using the Pentax lens in a situation where the spot does appear with the tamron lens?
Forum: Troubleshooting and Beginner Help 05-16-2018, 09:14 PM  
Dark circle in images from Tamron 17-50 f2.8
Posted By Digitalis
Replies: 21
Views: 2,641
It could possibly be an oil spot on the sensor itself. Particulate matter inside lenses has to be either at a critical point in the optical path or of an extraordinary size to be visible in photos depending on focal length and aperture.

Does the spot appear at apertures f/8>= ? If the spot appears at wider apertures, than this it is probably the sensor that is at fault: rather than the lens. The reason for this is the sensor stack is closer to the sensor than the rear element of the lens will ever get. Thus anything on the sensor stack will have a visible effect long before anything in the lens shows up. It is just a simple process of elimination.



By definition: Flare is non-image forming light, a dark spot indicates an absence of light. So calling it flare is a bit of a misnomer.
Search took 0.00 seconds | Showing results 1 to 6 of 6

 
Forum Jump


All times are GMT -7. The time now is 11:03 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top