Extension tube help!
Oct 1, 2018 17:37:07 #
I got some extension tubes (inexpensive Fotodiox) to go with the manual 50 mm lens I have been using in reverse.
But in trying it out I seem to get some ghosting in the photos.
Attached is a quick one of some black rice, with the smudge pretty evident throughout. No, it is not on the lens.
This one was shot with the sun to my right coming over my shoulder so it doesn't seem like it would be lens flare.
I am wondering if the inside of the tubes are too shiny and need a matte black finish to cut down on internal reflections. The inside has the usual ridges, but is a glossy black.
Can anyone offer an explanation/solution for this?
But in trying it out I seem to get some ghosting in the photos.
Attached is a quick one of some black rice, with the smudge pretty evident throughout. No, it is not on the lens.
This one was shot with the sun to my right coming over my shoulder so it doesn't seem like it would be lens flare.
I am wondering if the inside of the tubes are too shiny and need a matte black finish to cut down on internal reflections. The inside has the usual ridges, but is a glossy black.
Can anyone offer an explanation/solution for this?
Oct 1, 2018 17:42:11 #
Yes, this is a very good chance ......which is why bellows are preferred.
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Oct 1, 2018 17:46:27 #
was the lens fogged up,i have to put my camera out for about 20 minutes before i use it when its really humid.
Oct 1, 2018 17:52:05 #
imagemeister wrote:
thanks imagemeister. That is good to know.Yes, this is a very good chance ......which is why bellows are preferred.
Oct 1, 2018 18:05:19 #
Thanks tinusbum, but the lens is clean and I have never had this problem with the same lens without extension tubes.
Oct 1, 2018 18:40:57 #
Reflections off of internal glossy surfaces is a real possibility. To test, I suggest that you properly attach your 50-mm lens to the tubes, and take similar photos as above.
You will NOT have nearly the same magnification, but you may see internal reflections.
Also remember that a reversed lens positions the rear element (glass) outside of the normally shaded area, which can contribute to flaring.
For your info, extension tubes were designed to be used WITH macro lenses, not INSTEAD of a true macro lens.
In my opinion, reversing a lens with extension tubes is like putting knobby tires on a Buick to go off-roading. You can do it, but do NOT expect similar results to using equipment properly.
You should read this FAQ: Extension Tubes vs Bellows vs Tele-Extenders vs Thread-on "Close-Up" lenses http://www.uglyhedgehog.com/t-26496-1.html
P.S. - This is VERY important. Take advice from ONLY UHH members who have actually POSTED macro-photographs. Many UHH members are only book or i-net educated, NOT field-tested.
You will NOT have nearly the same magnification, but you may see internal reflections.
Also remember that a reversed lens positions the rear element (glass) outside of the normally shaded area, which can contribute to flaring.
For your info, extension tubes were designed to be used WITH macro lenses, not INSTEAD of a true macro lens.
In my opinion, reversing a lens with extension tubes is like putting knobby tires on a Buick to go off-roading. You can do it, but do NOT expect similar results to using equipment properly.
You should read this FAQ: Extension Tubes vs Bellows vs Tele-Extenders vs Thread-on "Close-Up" lenses http://www.uglyhedgehog.com/t-26496-1.html
P.S. - This is VERY important. Take advice from ONLY UHH members who have actually POSTED macro-photographs. Many UHH members are only book or i-net educated, NOT field-tested.
Oct 1, 2018 18:43:18 #
Can you try a different lens? Maybe try different combinations of the tubes?
Last but not least - vary the lighting a bit? Maybe something transparent or translucent and lit from behind the object?
Good luck with this issue.
Last but not least - vary the lighting a bit? Maybe something transparent or translucent and lit from behind the object?
Good luck with this issue.
Oct 1, 2018 19:09:14 #
You might find this post od interest: Lens Reversing Technique https://www.uglyhedgehog.com/t-273500-1.html
Oct 1, 2018 20:03:08 #
Nikonian72 wrote:
You should read this FAQ: Extension Tubes vs Bellows vs Tele-Extenders vs Thread-on "Close-Up" lenses http://www.uglyhedgehog.com/t-26496-1.html
P.S. - This is VERY important. Take advice from ONLY UHH members who have actually POSTED macro-photographs. Many UHH members are only book or i-net educated, NOT field-tested.
Maybe in your link you should talk about the differences in internal reflections between bellows and tubes and the dangers of these reflections ? You should read this FAQ: Extension Tubes vs Bellows vs Tele-Extenders vs Thread-on "Close-Up" lenses http://www.uglyhedgehog.com/t-26496-1.html
P.S. - This is VERY important. Take advice from ONLY UHH members who have actually POSTED macro-photographs. Many UHH members are only book or i-net educated, NOT field-tested.
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Oct 2, 2018 09:30:21 #
I have wondered if light gets in through the joins, I have made a band of thin leather and taped it around my tubes which, I believe, helps and makes the joins more solid. I have heard of using painters' tape around the tubes.
Oct 2, 2018 10:07:48 #
I tend to agree with your assessment of either internal reflection or EnglishBrenda's suggestion of light leakage through the tube connections. Both should be an easy fix to try. I'm new to the venture of macro photography myself however I understand how fugitive light disrupts the wanted light on the sensor and skews the results.
Oct 2, 2018 12:13:16 #
Thanks to everyone for the useful, and thoughtful remarks.
Many things to consider as possibilities. I will try to do a scientific study over the next few days when I can find the time.
Brenda, one quick study was to test your idea of light leakage. Lens and extension tube on, with the lens capped at the "front"...ie no light should be coming into the sensor...and the image is totally dark. So light leakage through the joints is not the problem. But thanks for the suggestion.
Many things to consider as possibilities. I will try to do a scientific study over the next few days when I can find the time.
Brenda, one quick study was to test your idea of light leakage. Lens and extension tube on, with the lens capped at the "front"...ie no light should be coming into the sensor...and the image is totally dark. So light leakage through the joints is not the problem. But thanks for the suggestion.
Oct 2, 2018 12:48:24 #
You can flock the inside surfaces with black, light absorbant material. Various options exist. A fairly simple one is ribbons of thin black velvet which can be had at a craft store. There are suppliers of more official flocking material for this sort of application, and this should be better at absorbing light. Here is one: http://www.fpi-protostar.com/hitack.htm You can buy the adhesive stuff by the inch. I have a roll myself for various old projects. But I found I needed to use glue to help hold it better.
It will be hard to say how good your set up is regarding image quality, until you resolve the glare problem. I heavily depending on a forward mounted 50mm on extension tubes for an extended time, and got good results, but felt that the IQ fell away if I pushed it much beyond 2:1.
It will be hard to say how good your set up is regarding image quality, until you resolve the glare problem. I heavily depending on a forward mounted 50mm on extension tubes for an extended time, and got good results, but felt that the IQ fell away if I pushed it much beyond 2:1.
Oct 2, 2018 16:12:32 #
imagemeister wrote:
Better yet, YOU write a stand-alone thread about "the differences in internal reflections between bellows and tubes and the dangers of these reflections." Include photographs showing different set-ups and comparative results. When your thread is ready, we will 'sticky attach' to first page of Macro Forum.Maybe in your link you should talk about the differences in internal reflections between bellows and tubes and the dangers of these reflections?
Oct 3, 2018 17:04:13 #
Not scientific but I put a bit of light absorbant material in the 28mm extension tube and took some shots with a reversed 50mm lens.
The shots with the reversed lens and tube regularly show a haze, although it is sometimes less obvious.
The reversed lens by itself can be very sharp and clear. I'll put a couple of other images in another post.
My guess is the problem is the extra light bouncing around between the lens and the sensor. With the tube, less of the light transmitted by the lens hits the sensor, ie more bounces around inside. As Nikonian72 pointed out, the reversed lens is not designed for this use and so probably lacks adequate baffles etc, letting in more stray light than the system can handle.
The inside of the extension tube was not completely covered by the absorbant material, I am going to try to cover as much of the surface as possible with either flat black paint or something else to see if that helps.
Summarizing - its not light leak, and its not the reversed lens itself.
Thanks all for the advice!
The shots with the reversed lens and tube regularly show a haze, although it is sometimes less obvious.
The reversed lens by itself can be very sharp and clear. I'll put a couple of other images in another post.
My guess is the problem is the extra light bouncing around between the lens and the sensor. With the tube, less of the light transmitted by the lens hits the sensor, ie more bounces around inside. As Nikonian72 pointed out, the reversed lens is not designed for this use and so probably lacks adequate baffles etc, letting in more stray light than the system can handle.
The inside of the extension tube was not completely covered by the absorbant material, I am going to try to cover as much of the surface as possible with either flat black paint or something else to see if that helps.
Summarizing - its not light leak, and its not the reversed lens itself.
Thanks all for the advice!
28mm tube, Haze is very evident
(Download)
28mm Tube, Haze less obvious but still there
(Download)
No tubes, Nice and clear
(Download)
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