Railfan Technology > Lens Flare?

Hi all--

I have a problem that I cannot seem to solve.  When I shoot extended exposures directly into a light source I end up with the two different spots on the image as can be seen in the attached photo.  The attached photo is a 90 second exposure, I was thinking of silhouetting the signal in the picture but ran into this problem.  A couple things have come to mind--

a. Would using a lens hood fix the problem?
b. Is this a result of a dirty mirror or sensor?

I have done a little research and lens flare is something I have considered.  However, from what I understand, lens flare comes from a light source that is not in the picture, such as the sun.  If that is the case, I do not think a lens hood would do anything because the spots are a result of the light source in the picture.  So I remain puzzled.

I appreciate any thoughts from all of you experts out there!  Jeff M.

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Do you have a filter on the front of your lens?

No, the only thing I have on the front is a transparent piece to keep the exposed part of the lens from getting scratched.  Should I try removing that?
 

jeffm238 Wrote:
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> No, the only thing I have on the front is a
> transparent piece to keep the exposed part of the
> lens from getting scratched.  Should I try
> removing that?

YUP! loose the filter! It is probably causing internal reflections. Try it without the filter.

Bob
>  

Shooting at an angle into a light source will frequently produce lens flare, even with the highest quality lenses.

Lens flares are caused by changes to the angle the light is travelling at each lens surface...surface to air, surface to surface, air to surface.  Each wavelength of light refracts at a slightly different angle.  That's the reason that camera lenses are carefully computer designed and take into consideration various wavelengths of light (colors) and how each one travels through each lens element as well as the lens as a whole.  Throw in a variety of lens coatings designed to prevent light from being reflected (like a pool ball hitting a cushion), either internally within a lens or off the surface of a lens/air interface.  

Camera lenses are designed within the constraints of capability, quality, and cost.  Obviously, lower cost lenses don't have the higher-quality or even 'exotic' glass elements or the very best coatings, and will thus suffer a slight image quality loss compared to a high-end ($$) lens of similar focal length(s).  Throw in that most zoom lenses cannot match the image quality of a prime lens (fixed focal length).  Add to that, the greater the zoom 'range' (30mm-300mm, vs 16mm-35mm, for example) the more 'compromises' must be made to achieve the greater range, resulting in less image quality.  Due to lower quality glass, coatings, and added design compromises, lower-cost lenses will also experience more lens flare than their more expensive breathren.

As mentioned previously, using a filter of any kind, and any quality in the front of a lens increases the likelihood of lens flare due to the added air/glass/air surfaces that the light must pass through.  As with lenses, the cheaper the filter, the more likely a degraded image or lens flare will occur.  So, ditch the filter.  Yes, if you bang the front perimeter of the lens, you'll likely bend and break the cheap protection filter.  At best, it'll easily unscrew and the tiny glass fragments easily removed from the front element of your lens.  More likely is that the metal ring of the filter will jamb into the filter threads of the lens and be exceedingly difficult to remove without a trip to the lens manufacturer, and 'powdered' glass may find its way into the internal workings of the lens. 

Which brings me to another point.  There is no such thing as a 'protective' filter.  In the film photography days, most photographers, myself included, kept a UV or Haze filter on my lenses not for protection, but for improved image clarity by removing various (undesired) wavelengths of light.  But these days, a UV filter is useless as the camera sensor has a built-in UV filter in front of it.  Unfortunately, the marketing whiz kids that package 'camera deals' with various filters, cleaning devices, and even carrying pouches are merely making a big profit for the company, and little benefit to the customer.  I only carry 2 filters, Circular Polarizers (CPL) of different diameters, that I use to cut down reflected glare off water or glass surfaces in the image.  I may start experimenting with Neutral Density (ND) filters, but for railroad photography, I feel there is little need for ND filters. 

The best 'protection' you can put on a lens is a lens hood!  If it takes a 'whack', it's less than $30 or so to replace the plastic hood.  My hoods have a number of dings in them from tables, doorways, and who knows what.  Sometimes it's difficult to move from here-to-there without hitting something.  I have yet to break a hood.  Also, the primary purpose for a lens hood is to prevent 'stray' light entering the lens.  Think of a street lamp at a 45 degree angle from where your lens is pointing that is not a part of the image.  Angular light from that street lamp will most likely be blocked by the lens hood, thereby preventing a likely lens flare.      



 



Edited 2 time(s). Last edit at 07/21/15 17:58 by BRAtkinson.

I'm beginning to think the extra lens element that is in an Image-Stabilized lens  (I'm a Canon guy) might sometimes cause more lens flare.  Case and point: I had a Tamron 17-50mm f2.8 Zoom Lens that was not Image-Stabilized, then I upgraded to the Image-Stabilized version.  The IS version is an overall bigger lens than the non-IS version and I ended up with nasty lens flare issues at night, though during the day, the lens was otherwise perfect!  This is a very sharp lens that is decently fast as at any focal length, your largest aperture can be f2.8!  I'm beginning to wonder why I ever went with an IS lens considering I've now learned that it seems to serve little to no purpose for railroad photography!  I guess you live and you learn, though some may disagree with me on that.

As I understand it, image stablization is accomplished using various motor/detector mechanisms that have nothing to do with lens flare.  Yes, minute internal lens movement is used to maintain stabilization.  But that movement is nearly imperceptable to the human eye. 

The goal of IS is to reduce camera shake-induced blur at slower shutter speeds, roughly 1/125 and slower.  Faster than that, camera shake bluring largely disappears, unless one is using focal lengths roughly 200mm and longer.  Keeping shutter speeds above 1/200 is typically necessary to 'freeze' moving trains (or cars).  Hence, IS on a lens for most daylight photography generally provides little benefit.  

I've successfully taken handheld pictures at 1/10 compliments of IS on the lens I was using.  Of course, at that speed, the non-blurred success rate was in the neighborhood of 1 out of 25, largely due to subject movement (and some of mine, too).  Regardless of what it is called - IS (Canon), VR (Nikon), VC (Tamron), or OS (Sigma) - provides anywhere from 2 to 4 'stops' of stabilization, allowing slower shutter speeds, thereby allowing smaller aperture settings and/or lower ISO speeds.

Of note is that most lenses that have image stabilization should have that function turned off when the camera is on a tripod.  I've read that the stablization mechanisam in some lenses get confused while tripod mounted and cause bluring because of it.    
   

As mentioned, you don't want anything over the lens.  The other is you are shooting pretty close up into the signals at 90 seconds? 
Didn't mention other data but the signal is clearly blown out exposure wise.  Comments I have read is that with the right(actually wrong) combination you
can induce these results in even the best equipment.  I'd get rid of the lens cover, and think about your setup, ie the angle you are shooting, how close you are tothe signals with time exposure etc and see what you get.

Bob

Thank you all for your helpful suggestions.  I intend to get out this weekend to the same spot and see what I can come up with.  I'll post my results so that you can see if I was able to make any improvements.

Jeff M.

It also shows the lens that are not coated..................Swede...........Albany,Or

I realize that many photographers will swear up and down that a filter on the front doesn't offer any meaningful protection, but I beg to differ. The instruction booklet/warranty information for at least one of my professional grade, Canon L-series zoom lenses clearly states that a UV filter must be applied to consider it fully "weather sealed." I have B+W pro filters on all my lenses, and don't have issues with flaring or ghosting. Problems mostly arise when people put low quality filters on a lens.

Posted from Android

I have taken pictures of bright light souces at night with a variety of lenses, with and without filters.  The quality of the coating on the lens elements, and the number of lens elements and groups, seems to be the most important factor in reducing lens flare.  You can think of it as the number of glass-to-air surfaces, including the filter, as one big factor, and the quality of the anti-reflection coatings as another.  For example using a Canon 28-135 IS USM lens, even with out a filter, gave me great big red blobs around the navigation lights on top of some tall wind turbines (see attached photo 1).  Shooting the same thing with a Canon 24-105 was much better, and shooting with a Canon 135 single focal length lens gave me nearly flare-less images (though I did get some interesting differaction spikes, see attached photo 2).  The 20-135 has more groups and cheaper coatings than the 24-105, while the 135 single focal length has great coatings and very vew lenses or groups.

If you are running into lens flares, it is all about the glass, number of air-glass surfaces, quality of coatings.  If you find yourself fighting lens flare, you need to change your glass.

Kit Courter
Menefee, CA
LunarLight Photography

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bioyans Wrote:
-------------------------------------------------------
> I realize that many photographers will swear up
> and down that a filter on the front doesn't offer
> any meaningful protection, but I beg to differ.
> The instruction booklet/warranty information for
> at least one of my professional grade, Canon
> L-series zoom lenses clearly states that a UV
> filter must be applied to consider it fully
> "weather sealed." I have B+W pro filters on all my
> lenses, and don't have issues with flaring or
> ghosting. Problems mostly arise when people put
> low quality filters on a lens.
>
> Posted from Android

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