15th August 2012, 12:50 PM
In this thread I hope to compare and contrast all the different macro set ups I can get my mitts on - bellows, extension rings, reversed lenses, microscope objectives and press-ganged enlarger lenses and so on.
But first a discovery. In my initial experiments, I found a nebulous white patch in the centre of images taken using a very cheap extension ring set. I thought the extension must be leaking light, and replaced the extension rings with a BPM Bellows. Not only was the white patch still there, but it had grown in size and density. Naturally I was dismayed, and ran round and round crying out "Mein bellows ist leaking! Mein bellows ist kaput! and other such nonsense.
After a cup of tea, I thought the matter through, and did some exposures with the lens cap on. This produced beautifully black frames, which could not have happened were both the extension rings and bellows leaking light.
I concluded that light was being reflected from the sensor back down the lens barrel before being partially reflected back at the sensor by the UV filter. I removed the filter and the problem disappeared. After more tea, I felt settled enough to proceed with my first experiment.
This Prussian silver coin is 18mm across.
Equipment and settings were:
7mm lens extension
Nikkor AI-S 50mm f/1.8 (manual only)
Exposure details: 800 ASA, f/11, 1/200th
Illumination: the gap between lens and subject was large enough to benefit from flash bounced off the ceiling. I used an old Nikon SB-20 speedlight on an extension cable lying face up on the carpet. After a few test exposures, I found the half power manual setting gave a fair result with the lens and film speeds given.
The camera was mounted on an enlarger stand by way of a Manfrotto monopod head, and brought to focus by twiddling the enlarger height knob. I didn't find it easy to gauge the best focus with this set up.
15th August 2012, 03:03 PM
Mexican 2 1/2 gold pesos 1945
In this test I have used the same rig described above, but with a 14mm extension tube.
Settings were Nikkor 50mm f/1.8 set at f/11.
Illumination was provided by a Nikon SB-20 speedlight set at 1/8th power, and held about one yard to one side of the subject.
Clearly, the lighting needs needs to be balanced better - to preserve the detail revealed by strong side lighting, but without creating such deep shadow on the unlit side - a simple reflector perhaps.
Last edited by Brocken; 15th August 2012 at 03:08 PM.
15th August 2012, 03:34 PM
If you want to have complete coverage of the subject you should consider the principle of using a long focus lens with either extension tubes or close-up lens. The drawback of doing it with extension tubes is that the longer the lens the more tube/bellows required. Depending on how powerful the CU lens used there may be some loss of IQ. The advantage of the longer lens is greater distance between subject and lens.
I have several sets of extension tubes as well as a bellows but they never get used .... they were purchased on the basis that perhaps it would be nice if I had them ... in case .....Normally I use a moderate CU lens, two dioptre, as the simplest way to work on either a 420 or 280 lens depending on camera being used. For my thoughts on the subject .....
15th August 2012, 03:55 PM
I've got +1, +2, +4, and +10 add on front lenses which came as a set, but forgot to mention them in my first post. It will be interesting to see whether there is any loss of image quality when using these, as compared with a bellows providing similar magnification. There's certainly a lot less mucking about with them!
15th August 2012, 06:12 PM
Christopher, that is a problem that has been bothering me for quite some time; and I was going to post a thread here to see if anyone knew what was going on.
Originally Posted by Brocken
I've found the same thing when shooting with my Nikon D700 using an adapted Olympus Auto Bellows and some Olympus bellows mount macro lenses designed for 35mm cameras. The white, circular patch looks like haze or fogging; I thought it might be light hitting the lens cross-wise from my lighting set up, or (worse case scenario) fungus in the lens elements.
Light reflecting back from the sensor... that's an interesting thought. I have no idea how I am going to deal with that; but I do manage to get some photo sequences where that isn't a problem so perhaps, knowing how the problem arises and that I can get around it, I can now experiment to find how to eliminate the problem in each and every case.
15th August 2012, 07:12 PM
Hi John, my experience with that centre fog is exactly the same as yours. I noticed that it was worst with bright illumination coming in at a steep angle - for example, from a ring flash, where the angle of incidence and the angle of reflection from the subject are close to 90 degrees.
In my case, removing the Hoya HMC UV filter removed the problem. A pal told me that so-called 'digital' filters, such as the Hoya Pro-1 Digital series are coated on the back (as well as front) in an attempt to stamp out this problem, which he reckoned was a well-known problem in DSLR design.
What bothers me is that this same problem has maybe degraded lots of my pictures, but at a much lower level, so as to avoid notice as a distinct fault.
15th August 2012, 07:30 PM
Queen Victoria Crown 1889
Queen Victoria Crown 1889
The diameter of this sterling silver coin is 38mm
A few months ago I bought a Sigma 28-200mm f/3.5-5.6 DL Aspherical Hyperzoom Macro for a few pounds in a charity shop, but didn't think to try it out until today.
For this picture, I set the lens at its closest working distance - about 50 cm - and bounced a manual flash off the ceiling.
It's better than I expected, which is good enough for me!
16th August 2012, 02:54 PM
Re: Queen Victoria Crown 1889
This is intriguing. I do a lot of macro and have never experienced this center fog. I often do macro with a UV filter on, and on both lenses (EF-S 60mm and EF 100mm L), the filters are Hoya HMC. I use filters because the hoods are impractical when photographing bugs, and I want some protection of the front element when focusing at that distance.
I don't use bellows or close-up lenses. For greater magnification, I use extension tubes, ranging from 12 to 68mm.
So the question I have is why other people are having this problem (which is unsurprisingly made worse by a filter) when I never have. I have a hunch that the missing variable is lighting. I never use a ring flash. Almost all of my macros have one of three kinds of lighting: natural lighting, artificial ambient lighting, or flash. For the artificial ambient lighting, I use halogen or incandescent lights that can be aimed, most often diagonally from the sides. Here is my setup for some recent flower macros. For flash, I use a highly diffused single 430EXII, held next to the end of the lens. My flash rig is built like this, but with a much smaller diffuser.
So, I wonder if the center fog problem is caused by undiffused lighting that is positioned fairly close to parallel to the lens, so that it can reflect off the sensor?
16th August 2012, 05:36 PM
Light sources at 90 degrees
I've been using a MK Digital eBox Plus lightbox for my macro work. I've had the greatest problems with the halogen lights, at 3200 degrees Kelvin and the least problem with the fluorescents at 6500 degrees Kelvin.
Initially, I thought that the problem was related to the color temperature of the lights and a selective reflectivity of whatever is causing the problem; but I also thought the issue might have been the placement of the lights, which are in the side walls of the lightbox and so are at 90 degrees to the camera. I had been trying to loosely place light shades on/over the lens but I am not thinking I am just going to get a short section of black PVC pipe and line it with black velvet.
The fluorescent lights of the lightbox are much more diffuse than the halogen lights and this might be why they are less prone to producing the white center fog/haze I've noted in some images. The fluorescents are also a much flatter light source so I would prefer to use the halogens, which give very nice surface definition to objects and which are particularly suited to objects that are reddish is color to begin with.
16th August 2012, 08:12 PM
Re: Light sources at 90 degrees
John and Dan, I've found a reference to this problem (link below) where the author reckons that this artifact is worse with older SLR lenses (such as the Nikon AI-S 50mm that I used) as DSLR lenses have an anti-reflective coating on the reverse side. It may be that a combination of reflection from the back surface of the lens elements and reflection from the filter acted together to produce the bad results seen in my case, which was much more diffuse than the specimen image shown in the article.
Last edited by Brocken; 16th August 2012 at 08:16 PM.
17th August 2012, 05:35 PM
George III silver shilling 1816
Poor George III was completely bonkers when this coin was minted in 1816, and had only four more years to live, but his life would have been shorter still had he been able to see the devilish chromatic aberration on this photograph.
Details are: D7000 + AF Nikkor 50mm f/1.8 set at f/11 + x10 close-up lens + daylight.
The x10 lens came as one of a set of four ( +1, +2, +4 and +10) which cost about £10 on ebay, so I suppose one can't be too unhappy at the chromatic aberration for such a modest price.
17th August 2012, 09:25 PM
Re: George III silver shilling 1816
Christopher, these images are just stunning! Beautifully photographed, great dynamic range, no specular highlights (not an easy accomplishment when photographing metal), great depth of focus - wonderful work!
Today, I purchased a section of black ABS pipe; some black velvet; and a can of spray adhesive. I am going to find out just what effect completely shielding the lens from any incident light coming from the sides has upon that white fogging patch; so I'll get back to you sometime next week with some results on that.
17th August 2012, 09:53 PM
Re: George III silver shilling 1816
Thanks for your encouragement, John. I still have a great deal to learn, but it's good to know I'm making progress.
Originally Posted by John Morton
I'm very interested to see how your experiment with the black pipe goes. I like the idea of conducting the light directly to the subject at a chosen angle, rather than having it bouncing around all over the place.
Tomorrow, I'll see if I can find the time to re-create the centre fogging phenomenom, so that other people will know what we're talking about.
18th August 2012, 12:10 AM
Macro Fogging Issue
Originally Posted by Brocken
Well if you are just starting into this kind of macro work I would have to say that you are already way ahead of the curve in this. It isn't an easy area to work within, and it is fraught with many pitfalls that you appear to have very skillfully avoided.
I purchased my first bellows back around 1978, and I am very definitely still learning how to do exemplary macro work!
I happened to have the external drive that I have stored my more recent digital macro shoots on handy, so I pulled up a series of images that illustrate the problem we have been discussing. I've just given these photos a very cursory edit, to set the white balance and little else except downsize them somewhat, but this does nicely illustrate the issue we have been discussing.
First, the object I am imaging:
Next, a close-up at maximum aperture and minimum depth of focus:
Then, a close-up with minimum aperture and maximum depth of focus:
Finally, the issue we have been discussing:
I looked for an image which included a scale of measurement but none was ready-to-hand.
Last edited by John Morton; 18th August 2012 at 12:16 AM.
18th August 2012, 09:27 AM
Emperor Napoleon Italian states 10 silver soldi 1810
The white fog has not appeared on this picture - taken using a 21mm extension - though I expected it would.
Napoleon looks a bit worn, but I'd be doing well to look so good in 202 years time. Is the device to the right of the date meant to look like a champagne glass being knocked over?
Nikkor 50mm f/1.8 AI-S manual
Extension tube 21mm
ISO 100 - f/11 on lens - 1 second - sunlight about 30 degrees.
I've said 'f/11 on lens' because the effective aperture is much smaller than this, owing to the extension, but I can't remember how to calculate it.
There is less CA on this image than I got from the +10 close-up lens fitted to the AF Nikkor 50mm. I'm still having trouble with the bright edge on the light source side.
John - I've just got visitors, so I'll get back to this later.
Last edited by Brocken; 18th August 2012 at 09:31 AM.
Reason: postscript added
18th August 2012, 12:45 PM
Problem: Queen Victoria Newfoundland silver 20c 1896
Here we can see a bluish fog beneath the Queen's bun, and reaching out across her neck - but by no means as bad as I saw it the other day when I was using flash.
Nikkor AI-S 50mm f/1.8
Extension tube 7mm
ISO 100 - f/8 on lens - 1.5 seconds - daylight from window
I did tests across the whole aperture range from f/1.8 to f/22, and the fog was present in all of them in roughly the same quantity so I do not think it can be reflection off the back of the diaphragm blades.
19th August 2012, 12:21 PM
BPM Bellows Magnification test 50mm
Being a bit of dunce in the calculation department, I thought I'd do a practical test of the actual frame width pictured at different settings when using the BPM Bellows with a 50mm full frame lens and the Nikon DX crop format.
This image of a metric ruler shows a frame width of 17mm with the bellows set at 5 cm - nearly the shortest the BPM bellows can go without the risk of squeizure - a life-threatening contraction of the bellows akin to a seizure in human terms, and almost as hazardous as extreme concertina, where the venerable, ancient fabric - often compared to the Turin Shroud - is stretched beyond endurance.
Here are more rational details:
Nikkor 50mm f/1.8
Bellows set at 5 cm
100 ASA - f/5.6 - 8 seconds - natural daylight through window.
Has that white worm beneath the number 90 crawled onto the image after exposure, or did I forget to give the subject a good puff of the rocket blower for the 99th time this week?
Last edited by Brocken; 19th August 2012 at 01:15 PM.
Reason: added missing details
19th August 2012, 02:55 PM
BPM Bellows Magnification test 100mm
At a bellows extension of 10cm, the 50mm lens is now capturing an area of about 10 x 6.5 mm on the DX sensor.
The very colours themselves are coming apart with this degree of magnification and 800 ASA.
Nikkor 50mm f/1.8 AI-S (manual)
Bellows extended to 10 cm.
800 ASA - f/8 - 8 seconds - natural daylight from window
I could very likely improve the image by adding some anti-vibration damping to the copy stand, so I could use a slower film and longer exposure - or, of course, by shortening the exposure with flash.
20th August 2012, 06:29 PM
Nikon D90 with BPM Bellows, cable release, and rocket blower
And what a ruddy miserable picture it is too! I have completely failed to capture the mysterious nature of the bellows, the rush of blood to the head, the fever of excitement and expectation which any real photographer would feel just by being in the same room as them! The picture is not even exposed properly! Booo-ooo-ooo!
20th August 2012, 11:55 PM
Re: Mein Bellows
The question of image quality ... I have not done any tests but simply assumed that it comes from the quality of the CU lens and personally I remain content with a 2 dioptre since greater powered lenses do seem to lack IQ, particularly around the edges. The lens needs to be more than single element and in this situation I have a LF camera lens giving me about 7 dioptre and with its multi element construction gives good IQ. So while the cheap amazon [et al] sets get one started I think you need to go to Raynox or other multi-element lenses if one intends to do a lot of this work, and Raynox costs not that much more, though from the one I saw it is rather small and wouldn't work on a large DSLR lens. If the CU lens is smaller than the camera lens one looses light transmission as if one had added another iris up front.