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05-28-2011, 08:52 PM   #1
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loved the idea of reverse-lens macro, BUT...

I'm a little confused about how to properly use this set-up. My wife randomly bought me a reverse ring adapter without my even knowing what it was for at first. After some searching around, I found out it was a way to put my lens on backwards for macro photography. Eager to try it out, I put on the adapter, attached my kit DA L 18-55mm lens and got ready to shoot. However, when I looked through the viewfinder I could see almost nothing (almost pitch blackness) - unless I was shooting directly at bright light -even then it was really really dark. I gave up quickly as my eyes were getting really tired and strained from trying to focus in on and see clearly the subjects I was attempting to capture.

Am I doing something wrong? Is there a way to let in more light so that I can actually see what I'm looking at through the viewfinder? It also seems that a lot of people use two lenses combined to take these kinds of photos, but is it a necessity?

05-28-2011, 09:02 PM   #2
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For a lens with no aperture ring (e.g. your DA L 18-55mm), when there is nothing to control the aperture (e.g. in the reverse position), the aperture of the lens is at the smallest.

No wonder the viewfinder is dark.

You may want to manipulate the aperture lever with a finger to open up the aperture.

But the problem is that except at max and min aperture, you don't really know the setting of the aperture of the lens.

If you want to continue with reverse lens, I suggest getting an inexpensive lens with an aperture ring (e.g. Pentax M-50 F/2.0).

For a lens with an aperture ring, when there is nothing to control the aperture, the aperture of the lens is the setting of the aperture ring. So to take a photo with a lens with aperture ring, you use the lens' aperture ring to set the aperture you want to use, then use a finger to fully open the lens (using the lens' aperture lever) to focus, then release the finger so the aperture of the lens can fall back to the set aperture value, then shoot.
05-28-2011, 10:18 PM   #3
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Fantastic - playing with that aperture lever changed everything! Now I can see Now what I'm finding is just how difficult it is to hold the camera steady when getting soooo close to a subject. I'm guessing SR doesn't work when putting a lens on backwards? I never tried it, but was figuring it probably doesn't work when in reverse with a lens.
05-28-2011, 10:48 PM   #4
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QuoteOriginally posted by slr_neophyte Quote
Now what I'm finding is just how difficult it is to hold the camera steady when getting soooo close to a subject.
This applies to macro photography in general, not just for reversed lenses. Sooner or later, you'll realize the needs for tripod, ring flash, and macro focusing rail.

QuoteOriginally posted by slr_neophyte Quote
I'm guessing SR doesn't work when putting a lens on backwards? I never tried it, but was figuring it probably doesn't work when in reverse with a lens.
That's correct, in order for SR to work, the body needs to communicate with the lens. For reversed lens, there is no communication. In my experience, at macro distances, SR (with a macro lens) does not help as much as it does in general photography.



05-28-2011, 11:51 PM   #5
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slip a piece of rubber or plastic tubing over the reversed lens' aperture lever to control it. Friction between the tube and the lever's shield will hold the lever in place. To avoid diffraction softening you'll want to shoot with the kit lens aperture open.
05-29-2011, 01:42 AM   #6
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QuoteOriginally posted by SOldBear Quote
... in order for SR to work, the body needs to communicate with the lens. For reversed lens, there is no communication.
Well, that's not quite right. SR depends on the focal length, not on communication. I use many M42 and K- and M- type lenses that don't communicate. But SR *is* ineffective with very close work; the user's manual even says so. Put an A-type or AF lens on A-type or AF extension, so the lens communicates but is within macro range, and SR *still* won't work.
_____________________________________________________

Reversing a prime lens means working close, under 50mm / 2in. This is fine for setup studio work, not so fine for handheld and field shooting. Reversing a zoom gives more flexibility, especially non-DA zooms in the right focal range, with actual aperture rings.

I have a cheap old A35-80, a kit.lens that is arguably one of the worst Pentax ever sold. Ah, but reversed, it is sharp! At 35mm it reaches 2:1 magnification at ~5cm; at 80mm it focuses from ~150cm to beyond infinity, so can also be used as a portrait lens or short tele. The DA18-55 reversed doesn't have that range, and aperture control remains a PITA. So I just don't reverse the 18-55.

Last edited by RioRico; 05-29-2011 at 03:19 AM.
05-29-2011, 04:50 PM   #7
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SR is ineffective anyway and you must turn it off when you do use a tripod which is highly suggested you use for macro.
That's a good tip Newarts! Better than tape!
08-30-2011, 09:22 AM   #8
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Just curious, what mm value would you theoretically need to set SR at for say 50 reversed onto 100 (2:1)? I appreciate it might not be effective but even breathing gives me a wobbly image so this must be worth at least testing - anyone have an idea/equation?

08-30-2011, 09:47 AM   #9
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QuoteOriginally posted by Nass Quote
Just curious, what mm value would you theoretically need to set SR at for say 50 reversed onto 100 (2:1)? I appreciate it might not be effective but even breathing gives me a wobbly image so this must be worth at least testing - anyone have an idea/equation?
The distance from lens to sensor hasn't changed much so 100mm is appropriate. For SR it is the distance from lens to sensor that counts.

Last edited by newarts; 08-30-2011 at 09:52 AM.
08-30-2011, 11:07 AM   #10
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Ahhhh, thank you. But, surely it also needs a fairly serious modifier based on the mm of the reversed lens? As in, the smaller the mm you have on the reversed lens, the greater the focal plane displacement for every degree of arc movement?
08-30-2011, 11:26 AM   #11
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for the record, SR does not fully apply to macro work.
08-30-2011, 11:28 AM   #12
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REmember, you've essentially created a microscope and you'll have to be a specific distance from the subject. You could make a jig to align your lens or at least give you an idea of the photographic field to help you compose your subject. That's pretty much what a stage or platform microscope is.
08-30-2011, 12:23 PM   #13
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QuoteOriginally posted by Nass Quote
Ahhhh, thank you. But, surely it also needs a fairly serious modifier based on the mm of the reversed lens? As in, the smaller the mm you have on the reversed lens, the greater the focal plane displacement for every degree of arc movement?
It turns out that no modifier based on lens focal length is needed for the following reasons...

The way the Shake reduction algorithm works is to imagine the camera is rotating up & down (or side to side) around the lens like a see-saw (teeter-totter) at particular speed. The distance the end of the see-saw moves is proportional to the distance from the end of the see-saw to the lens. That's where the normal hand-held speed is proportional to focal.length rule comes from.

When a lens is focused at something far away the lens to sensor distance is one focal length; that's why you normally enter 50 when using a 50mm lens. But if you are doing macro work you enter the actual distance from the lens to sensor.

Say you have a 50mm lens and you extend it another 40mm with extension tubes. You'd enter 50+40=90mm

Say you have a 50mm lens and you don't extend but put on a 25mm reversed lens. The distance is still 50mm so you enter 50.

Say you have a 50mm lens extended 40mm and put on a reversed 25mm lens. You'd enter 90mm.

In your original post you said you added a 50mm lens to a 100mm lens for a magnification of 2 - that implies you didn't increase the distance beyond the original 100mm. But if you do increase the distance by 50mm you'd enter 150mm.

Last edited by newarts; 08-30-2011 at 02:27 PM.
08-30-2011, 01:12 PM   #14
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basic macro math

QuoteOriginally posted by Nass Quote
Just curious, what mm value would you theoretically need to set SR at for say 50 reversed onto 100 (2:1)? I appreciate it might not be effective but even breathing gives me a wobbly image so this must be worth at least testing - anyone have an idea/equation?
Here's the simple math of what's going on - two equations are involved (thin lens approximation)

image.distance = focal.length(1+m) m is magnification

Lens extension
When the image.distance = focal length, m=0. Now say you increase the image distance to focal.length + extension:

focal.length + extension = focal.length(1+m.extended) or:
m.extended = extension/focal.length

Lens stacking:
Another way to change magnification is to change focal length but not image distance.When lens f' is stacked onto lens f a new lens is formed with a new focal length f"

f" = f'f/(f+f' -d) where d is the spacing between the two lenses, usually assumed to be zero.

say an original lens f is focused at infinity so its image.distance= f then we stack on another lens f' to make a new lens f"

image.distance = f = f"(1+m.stacked) or after some algebra:
m.stacked = (focal.length.original-d)/focal.length.stacked

Combined extension and stacking:
If the original lens is extended and a second lens is stacked, macro properties change like this;

(1+m.total) = (1+m.extended)(1+m.stacked)

image.distance = focal.length.original(1+m.extension)

f-stop.effective = f-stop.original(1+m.extension) SR setting
08-30-2011, 01:18 PM   #15
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Lowell is right...

QuoteOriginally posted by Lowell Goudge Quote
for the record, SR does not fully apply to macro work.
SR can reduce nodding and side-to-side motions of the camera but not in-out motions which are important for macros because depth-of-field is very small.
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