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01-07-2011, 02:27 PM   #46
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An easy way to think of 1:1 or life size is that with your lens set at 1:1 the subject in the frame is the same size as the frame/sensor.

Life size in 35 mm would be the first image, the second is life size for a 4/3 sensor 17.3X13 mm the third is with a 1.4 tele converter and the forth is the tele converter plus a +6.5 diopter. If you want to see what your lens will do at closest focus set it to manual rack the lens out to 1:1 and then see how large a bill or coin is when you move the lens into focus.

Life size for the APS-C size sensor in the K-5 would be between the size of image one and two.

Phil Rudin

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01-08-2011, 07:17 AM   #47
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Hey again guys i think im lost again.

Option 1

Sigma 2.8 105mm

option 2

pentax 2,8 100 mm wr,

what do u think ?
01-08-2011, 07:54 AM   #48
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Both the Sigma and Pentax should be fine pieces, can't really go wrong between them. WR is sealed, if you need that, if not, you'd probably be better off with a macro lens that has an aperture ring (for use with tubes and bellows). As for sample images with the Sigma, these tend to be convincing [IMO :-) (I ended up with the Pentax DFA 100mm, but merely by change as the right second hand deal came by first with that, might have gotten the Tamron 90mm or the Sigma 105mm as well based on reviews in general and pictures here: all three would seem to be excellent choices)].

Last edited by jolepp; 01-08-2011 at 08:01 AM. Reason: +[]
01-08-2011, 10:12 AM   #49
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Exacta to Pentax?

QuoteOriginally posted by aliasant Quote
Lol

I wish it was that easy. Just buy this..... but there are so many ways to the bugs
I dont think you will need to get much closer the 1:1 if your shooting freehand.
That bug image in my previous post was shot at about 1:1 and I then cropped of the sides and rotated it a bit so that image is probably only 40% of the real frame.
Maybe you should just get the Sigma 105mm 2.8 Macro lens?
I have seen others get great results with it.
It goes down to 1:1 so that will get you far.
If you need to get closer just put a reversed, smaller lens on top of that.

Just for fun....
Heres another way that I havnt really tried in the field yet.

I use an old Exakta lens that has a nice and big button to close down the aparture. The lens is a Carl Zeiss Pancolar 50mm f2.0 that you should be able to find on fleebay or similar.

It can be used on extension tubes both normal and reversed.
You will get a lot closer if you reverse it so thats probably the best way to go.

Heres my lens with a total of 50mm tubes. Not reversed.
This is great for flowers and similar when you dont need to get that close and theres no bug to scare of.





Heres a full frame of that kit but reversed on a 20mm extension tube + a flash. Click on it to see the full version.




Heres the same shot cropped 100%.
My focusing skills on this shot wasnt that great though.




The great thing using these old Exakta lenses is that big button.
I hold my thumb on that one while trying to find the focus/distance and this is with the lens fully open. When I think I found it I press the button to close the aparture and then take the picture with flash. I used f8 or maybe 11 on this picture.
I have never tried a ring macro flash so I cant say what the result would be. My flash is an older Pentax AF240Z. I use it slightly pointed up so that I dont get the direct hard light. Putting a diffuser on it works great too.

How do you get the Exacta mount to fit on a Pentax?

01-08-2011, 10:47 AM   #50
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QuoteOriginally posted by chuck luck Quote
How do you get the Exacta mount to fit on a Pentax?
Well.

I learned this from some forum thread and it actually works pretty well.
Infinity might need some kind of adjustment but sometimes it works without.

Take a m39 to m42 adapter. Buy it on fleebay or similar.
It is just a thin ring with internal 39mm thread and external 42mm thread.
Glew it onto the exakta mount like in the picture.

I cant use this as a normal M42 lens because the shutter button is in the way but with some m42 tubes it can be used anyway.
Atleast as a kind of macro lens.
There are Exaktas that doesnt have the shutter button and they can be used pretty much as any m42 after this mod.

If I would use this for macro I would use it reversed so then I wouldnt even need the m42 mod.

Last edited by aliasant; 02-19-2013 at 10:21 AM.
12-20-2011, 12:54 AM   #51
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QuoteOriginally posted by aliasant Quote


Heres my lens with a total of 50mm tubes. Not reversed.
This is great for flowers and similar when you dont need to get that close and theres no bug to scare of.
Thank you very much for your suggestion. I want to go more into flower photography, therefore this is very helpful. Macro photography is a new topic for me and I wasn't sure with which lens I should start because the variety of options is big. Because it's winter now, I thought it would be the best idea to practice with flower bouquets from a flower delivery in uk. Then I have an assortment of flowers and can take many different pictures. But of course I will also have to learn more about the technical side, before the outcome will be good.
12-20-2011, 01:49 AM   #52
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QuoteOriginally posted by chuck luck Quote
How do you get the Exacta mount to fit on a Pentax?
There's a little more. First, avoid Exakta-mount lenses with the stop-down button. And if you ever wish to sell the lens, remove and save the index screw on the lens base. The rest of the adaptation is non-destructive. As aliasant said, use an M39-M42 adapter ring, very cheap. Use contact cement (dissolvable in nail-polish remover) to glue the ring around the lens' bayonets. After it dries well, like about a day or three later, put a cheap clone M42-PK adapter on it for close-focus work.

If you want infinity focus, that's pretty easy: Tape a piece of 100-grit (rough) sandpaper to a very flat hard surface, like a kitchen tile. Get a cheap clone M42-PK adapter and a small chunk of white pine or a large rubber eraser. Use that to preserve your fingers as you press down on the adapter while you grind away at the wider (flange) side of the adapter. Remove about 0.6mm from the adapter. If you don't have a micrometer to measure it, blow away the metal dust every now and then and test-fit the lens to your camera, checking for focus on some distant object.

QuoteOriginally posted by ptaylor Quote
I want to go more into flower photography, therefore this is very helpful. Macro photography is a new topic for me and I wasn't sure with which lens I should start because the variety of options is big.
Macro is good for shooting floral anatomy -- the pistils, the stamens, the sex lives of plants, ooh ooh! Just like macro is good for shooting eyeballs. But to shoot faces, or flowers, a close-focus lens is more than sufficient. The kit.lens focuses to within about 250cm / 10in. Any manual lens can be easily converted to close-focus by just adding a thin macro tube behind it. To shoot real close with an A-type or AF lens, get a cheap used A-type 2X TC and remove its glass -- that provides plenty of extension for many lenses.

I hope this doesn't overwhelm you: https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html
12-22-2011, 06:37 AM   #53
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practise, practise, practise

12-22-2011, 06:51 AM   #54
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I have an FA-100 macro, it performs very well for me. The stand-off distance is vital if you want to shoot insects in the field, and if you do see a bird or something, that 100mm is a decent telephoto with a LONG focus throw.

Reversed-lenses are great, but they're essentially microscopes and the subject distance from the lens is fixed. (I think my optics understanding is correct). Bees won't sit still long enough for you to make that work. OK, sleeping male bumblebees will sit still long enough, but since they're usually under leaves or flowers, getting a shot of them with bellows or long rigs will not be easy.
12-23-2011, 07:54 AM   #55
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reversed lens working distance...

QuoteOriginally posted by TER-OR Quote
....
Reversed-lenses are great, but... the subject distance from the lens is fixed. .
That's true only when the lens is reversed onto another lens and both lenses are focused at infinity.

A reversed lens by itself acts like a normal lens (light does not know which direction it is traveling through a lens.)
12-23-2011, 10:33 AM   #56
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QuoteOriginally posted by TER-OR Quote
Reversed-lenses are great, but they're essentially microscopes and the subject distance from the lens is fixed. (I think my optics understanding is correct).
Quite right. The working distance of a reversed non-zoom is that lens' register; Pentax is 45.46mm. That's the same whether the lens is simple reversed on the mount, or reverse-stacked onto another lens for more magnification. Why? The lens is designed to project a flatfield image at that distance, onto the camera frame (the image field) in normal use. Reverse it, and it's the distance of the subject field. EDIT: Ignore.

Reversed zooms are different. My fave example is my crappy A35-80, arguably the worst lens Pentax ever made. But it is sharp reversed. Working distance varies from around 35mm at the short end to beyond infinity at the long end -- a true macro-zoom!

QuoteQuote:
Bees won't sit still long enough for you to make that work. OK, sleeping male bumblebees will sit still long enough, but since they're usually under leaves or flowers, getting a shot of them with bellows or long rigs will not be easy.
My cheap trick here is to use a longer enlarger lens on extension: bellows+tubes. Even 100mm may put you too close for the bees. The price differential between a 150mm macro lens and a 140-160mm EL with extension is enormous.

Last edited by RioRico; 12-24-2011 at 02:19 AM.
12-23-2011, 12:11 PM   #57
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We've two statements of fact here in direct conflict. I hope I can straighten it out...

QuoteOriginally posted by newarts Quote
That's true only when the lens is reversed onto another lens and both lenses are focused at infinity.

A reversed lens by itself acts like a normal lens (light does not know which direction it is traveling through a lens.)
A lens on a bellows acts qualitatively the same regarding working distance whether the lens is reversed or not. That is, increase the length of the bellows and the working distance gets smaller as the magnification gets larger. As the bellows gets very long, the magnification approaches infinity and the working distance approaches the lens' focal length.

Let's review the meaning of "working distance"; it is the distance from the "lens" to the subject - well actually it is the distance from where the lens appears to be in space to the subject. This imaginary location is called the front or rear Principal plane depending on which side of the lens you look at. It can be inside or outside the physical lens depending on how the lens is designed.

A camera lens is designed so infinity focus puts the focal point on the sensor. A wide angle lens has a short focal length. If this focal length is shorter than the camera's registration distance the Rear Principal Plane is designed to be inside the camera, one focal length from the sensor. Consider a 30mm lens designed for a Pentax type K camera (registration= distance from mount to sensor=45.46mm) - the lens is designed so its rear principal plane is 30mm in front of the sensor which is 15.46mm behind the physical lens.

The optics equation for working distance is:

Working.distance=Focal.length(1+1/m)

Say we put this lens on a bellows and adjust it so m = 1, ie 1:1

The equation says the working distance is 60mm (focal.length(1+1)) - but this is the distance from the rear principal plane to the subject. Now remember the rear principal plane is 15.46mm from the lens mount so the actual clear distance is 60+15.46=75.46mm

You can see from the above example that the only time the clear distance between the subject and lens mount is the registry distance is when the magnification is infinite.

The registry distance is the lower limit of clear working distance for a reversed lens.

I hope this helps clear up the approximation that the working distance for a reversed lens is the registry distance.

There is one common setup when the clear working distance is the registry distance; that's when a lens focused at infinity is reversed onto a primary lens focused at infinity.

Last edited by newarts; 12-23-2011 at 11:16 PM.
12-23-2011, 09:19 PM   #58
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QuoteOriginally posted by yeatzee Quote
All of my macro's are taken far closer than "at least 10-20"" and I seem to do fine Its all about stalking technique and patience

To the Op: I use A: Pentax F 28mm reversed on extension tubes or B: broken M 50mm F/1.7 reversed on extension tubes or C: F 135mm with a 50mm or 28mm.... this is all depending on the subject and magnification needed. I also own a macro lens (sigma 105mm) but it is never used. I prefer the challenge and rewarding experience when getting shots with my ghetto setups (plus I hate 1:1)

Really, in macro most of it depends on your lighting setup. Even at 1:1 i suggest using a flash. As you get more and more magnification, the more light you will need.

Here's a couple of my images using my various setups:













etc. etc.

(also, I use those cheap $10 extension tubes....)

(edit: This thread makes me want to go out again and take some more.... haven't done it in a while. Im going to be buying a focusing rail here pretty soon so expect some heavy stacking in the next couple of weeks)

yeatzee has some of the best macro shots that I have seen! EVER!
05-23-2012, 06:04 PM   #59
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Hi guys...I have a question for all of you who are using a reversed 28mm lens for mycro photography. I have a Sigma Mini Wide II 28mm f/2.8 M42 manual lens which I use reversed with some extension tubes. And I have one problem that occurs and I don't know how to solve it. Problem is that on my images very often there is a white spot in the center of image. Something like white shadow if you know what I mean. That is a problem because I lose details in that area.

I don't know is flash causing this or what? I use on camera flash, but with DIY diffuser which I use directly over my lens for better lightning of my subjects. I don't know is this a lens problem, or something else.
Another thing that sometimes happens is that If I shoot for example and spider on a wall, and that wall is orange, my whole image is orange too? Some strange reflection it seems? Is this normal with all reversed lens, or I need to buy myself another manual prime lens?

I hope soon I will by myself a Pentax SMC 28mm f/3.5 lens, because they say this is a great lens for reversed macro.

Can you recommend me some other 28mm lens which have good sharpness and image quality? Maybe Vivitar has something comparable to Pentax SMC 28mm?

Here you can see my images that I have taken with Sigma 28mm(I made an error and under every image I have written that I have used 24mm lens, but it is 28mm)
My flickr macro gallery

Here are some examples where my subject is colored like background where he is standing:

Here is a reddish glare on jumping spider

And here everything is a too much blue
05-24-2012, 04:38 PM   #60
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I thought this macro stuff would be easy. Not. Heres a few form today. 1st attempt at macro.
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