Reflections in a 50/1.4...

[Uffe]

Hi all,

I have a problem with my 50mm 1.4 lens. It shows reflexes that appears to come from somewhere within the lens, but I'm not quite sure what's up... The reflexes always appear in low-key pictures with strong lights in them. Take a look at this example:

http://www.zetterlund.com/reflexes.jpg

...as you can see the the lights are reflected through origo of the picture.

Could it be that I have a 50 mm where they forgot to coat one of the lenses or something? Or are all of those lenses like this? It is effectively impossible to use this lens at night, since street lights etc always ruin the images.

Anybody have a clue or suggestion?

/Uffe.

[Rudi]

Uffe,

if they forgot to coat yours, then they forgot to coat mine, too... :)

I am getting some reflections even if I use my lens for long-exposure astrophotography, and there is a bright object, such as Jupiter, in the frame. It's usually worse if the bright object is to the side of the photo, then you can just expect a "bounced" reflection on the other side of the frame.

I always thought it was my UV filter (I use it to protect the lens from the elements, especially on those humid, dewy nights), and plan to take it off and shoot some test frames to see if things improve.

Do you use a filter on your 50/1.4? If so, take it off and let us all know if things get better.

HTH,

[Uffe]

Thanks Rudi,

I have been thinking along the same lines... What I do see is that the slower the shutter speed the more prominent the reflections are... Although they don't have to be very slow to produce reflections. My included sample was shot at 1/15.

And yes, there is a protective skylight filter at the front of the lens. I will do some tests asap and see what happens. (Not tonight though, it is 1.40 AM here...)

I'll post my results.

/Uffe.

[karlg]

Yes, take the Filter off, THAT is the most likely problem. Unless you have a high quality multicoated filter, that is most likely what the problem is. What you are likely seeing is the the light bouncing off the front element of the lens, to the back side of the filter and then back into the lens.

I think most good photographers forget the filters. A lens hood gives better protection in some ways and never hurts the image.

Karl

[Scho]

I had a similar problem using my 50mm 1.4 with a Hoya R72 IR filter (see this thread: http://www.dpreview.com/forums/read.asp?forum=1019&message=2569413)
I concluded that there was a reflection off the rear element of the lens. Using the same filter on a 28-135, 135 2L, and 20 2.8 I did not see this reflection, so perhaps the 50 1.4 is particularly prone to this internal reflection problem with filters.

[Uffe]

Hi again,

and thanks for all the replies. Yes, it was the filter.

I'm normally a Hoya HMC kind of guy, but the day I bought my 50 mm they were out of stock on Hoyas. So I picked up a Soligor instead just for lens protection. Then I forgot all about it - until now...

My testing showed me:
- Soligor filter: Extreme reflection
- Hoya HMC filter: Slight reflection, but not really noticable in the final picture
- No filter: Very slight reflection, not noticable in final picture

All testing were done under extreme conditions, straight into a strong lamp in an otherwise dark room.

Could someone please pass me some vaseline, I'm going to turn my Soligor into a soft filter... :)

Thanks again,

/Uffe.

(Oh, almost forgot - I managed to get reflections from the soligor on my 28/1.8 too - so it's not specific to the 50/1.4.)

[Rudi]

Uffe,

thanks for the update. I don't know whether to feel proud of the fact that I suspected the filter in the first place, or stupid for putting that cheap filter on my 50/1.4 in the first place... :)

I usually use Hoya HMC as well, but slapped this one on the 50mm when I wanted to protect it from the moisture one night, because I just happened to have one from years ago, and it was the right size. After that, I never got around to replacing it with anything else...

Oh well, live and learn... :)

[jdavis]

Uffe wrote:
I'm normally a Hoya HMC kind of guy, but the day I bought my 50 mm they were out of stock on Hoyas. So I picked up a Soligor instead just for lens protection. Then I forgot all about it - until now...


Better yet the Hoya Super HMC UV filter, and best the Hoya Super HMC Pro (1mm filters).

For an interesting test involving the Super HMC UV see the Multicoated Filter Test link on the following page (right top column):

http://www.michaeltapes.com

John

[Uffe]

Thanks guys,

a lesson learned (again). It annoys me quite a bit that the quality of the filter had that much impact... It wasn't that much cheaper than a Hoya.

Thanks for the link, John. Interesting results, indeed. Definitely proves the point.

Anyway, I would still rather put on a cheap filter than have no filter at all. *Twice* in my 20+ years with SLR's I have had filters rescuing lenses that would otherwise have been smashed... :p

But the next time, I'll replace the cheap filter sooner...

/Uffe.

[Rudi]

Today I ordered Hoya HMC's for all of my lenses that don't have them on yet (replaced even the regular Hoya filters, which aren't bad, but the HMC's are that much better again).

Didn't have to go out of my way too much, either, as I was picking up a new 70-200mm f/4 L anyway... :) :)