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09-30-2009, 08:13 AM   #1
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Macro help? (lots of questions)

Hi,
I have been getting some great help from this forum! Thanks to everyone However, the complete newbie that i am, i am still lost in a lot of places.

I have been researching macro gears for a few days now, trying to see what is out there....also a thread on this forum yesterday lead me to want some extension tubes.

I do have some difficulties, a lot of the pictures of bellows, macro rails, etc, are of these accessories, and i dont exactly know how people are using it.

So here are my questions or findings....please correct me if i am wrong :
- Closer inspection of macro rails seems to suggest that it sits on a...tripod, and it basically moves the camera back and forth to help with focusing?

- Bellows also sit on the macro rail, and ...(help me here) errr, is basically what extension tube is...except its on this accordion shape that allows it to be further extended or reduced, unlike a fixed extension tube...

- extension tube will help me with my image magnification....and the magnification, people are giving examples, would be the: extension tube mm/the lens focal range mm.....so 50mm extension tube / 50 mm prime lens = 1:1 magnification, regardless of the existing prime lens magnification.

What would this mean if i have a dedicated 1:1 90 mm macro to begin with?

- Also, the working distance for this dedicated macro i am using, as i find out, is painfully small. (maybe several inches?). Is there a math to calculate how much will be cut by the extension tubes?

- Currently, i am overexposing all of my shots with on-board flash...with a longer extension tube, am i correct to assume that this will be less of a problem ?

- To compensate for the working distance lost by extension tube, can i use teleconverter? a 2X teleconverter will convert my 90mm into a 180mm ...is this correct? How would this then affect the magnification achieved by adding the extension tubes?

- What will all of this mean to my image quality? (if i set a dedicated macro with extension tube with teleconverter)

- Am i correct to assume that for insect photography (live, in nature), i would not need macro rails and bellows because its just impractical and impossible to take picture of a moving object....

Thanks!! i know i ask a lot of questions, but i am convinced that i am working with some of the most helpful group of people around this side of earth

09-30-2009, 08:33 AM   #2
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I've never used any of the devices you mention, but I can answer several of your questions, based on the following fundamental principle:

Magnification comes from two things and two things only: focal length and distance. The greater the focal length, the greater the magnification for the same working distance. And the shorter the working distance, the greater the magnification for the same focal length. The only way you increase magnification is by changing one of those two things - increase focal length or shorten working distance. That's all there is. So anything done by a macro lens or any macro utility like extension tubes can be understood completely by understanding what it does to working distance and focal length.


QuoteOriginally posted by D4rknezz Quote
- extension tube will help me with my image magnification....and the magnification, people are giving examples, would be the: extension tube mm/the lens focal range mm.....so 50mm extension tube / 50 mm prime lens = 1:1 magnification, regardless of the existing prime lens magnification.
That's true *when you focus the lens at infinity*. When you focus closer than infinity, magnification is correspondingly greater, because working distance is smaller.

QuoteQuote:
What would this mean if i have a dedicated 1:1 90 mm macro to begin with?
Since a macro lens can focus more closely than regular lenses without tubes, it will also focus more closely than a regular lens with tubes. Meaning that if a regular lens with a given amount of extension did 1:1 when focused at infinity and 2:1 at it's minimum focus distance, the macro lens would do 1:1 at infinity but might be good for 3:1 at it's minimum focus distance, which will be shorter than the regular lens'. Those numbers entirely made up; I have no idea if the actual magnification you could expect would be greater or less than 3:1. I also have no idea how to compute what the working distance at minimum focus distance would be with tubes.

QuoteQuote:
- Also, the working distance for this dedicated macro i am using, as i find out, is painfully small. (maybe several inches?). Is there a math to calculate how much will be cut by the extension tubes?
If your 90mm macro does 1:1 at minimum focus distance, then that is the working distance required to do 1:1 at 90mm, period. So whether you do it by shooting without tubes at minimum working distance or with tubes at infinity, working distance would have to be the same. So if you need to be 3 inches away (or whatever) to get 1:1 without tubes, you'll need to be 3 inches away to get 1:1 with tubes. And you'll need to be closer still to get greater magnification.

QuoteQuote:
- To compensate for the working distance lost by extension tube, can i use teleconverter? a 2X teleconverter will convert my 90mm into a 180mm ...is this correct? How would this then affect the magnification achieved by adding the extension tubes?
You can certainly use a TC, but it's not going to "compensate" for the lost working distance. Working distance will remain *exactly* the same, TC or no TC. Doubling the focal length at the same working distance essentially doubles the magnification. Actually, I'm not sure it always works out that simply, but if you're looking for a rough estimate, that works.

QuoteQuote:
- What will all of this mean to my image quality? (if i set a dedicated macro with extension tube with teleconverter)
Extension tubes have no optics and thus don't really affect IQ. IQ with a TC invariably suffers; how much so depends on the TC.
09-30-2009, 09:17 AM   #3
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Ahhh....this kind of explain some things to me. So let me see if i get this correct :

So the teleconverter is not to compensate, all it does is help the magnification, the same with the extension tubes.
The difference is :

- Extension tubes *allows* me to get closer than the lens minimum working distance (effectively adding to magnification with no loss of image quality)
- Teleconverter allows adding magnification but does not change my lens minimum working distance (however, i have some loss of image quality)

Basically, by adding tubes and teleconverter, all i do is adding magnification by several order?

errr : what is focusing to infinity? I hear this alot, but i am not sure what that means...does it mean i am focusing to the far horizon? Sorry, i am a bit confused with this term.
09-30-2009, 09:33 AM   #4
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Yes, it means focusing to an object as far as your eye can see - like to the moon and beyond...
The horizon (and for most lenses anything beyond about 30m) is considered at infinity as well...

09-30-2009, 10:10 AM   #5
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If you look at the focus scale on the lens itself, you'll see markings showing the current focus distance as you turn the focus ring. And when you focus as distant as the lens can focus, you'll see it is usually marked "infinity" (sideways 8).

Last edited by Marc Sabatella; 09-30-2009 at 06:23 PM.
09-30-2009, 11:24 AM   #6
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Ah thanks! That clarifies it for me. I am glad you pointed to the barrel of the lens too, because i have always puzzled over it but never wondered/focused on trying to read the numbers >_<
10-02-2009, 04:23 AM   #7
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Maybe this will help visualize how everything comes together. Here is a shot of my basic setup.

10-02-2009, 09:48 AM   #8
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Thanks for that image! Now i see how things are put together.

Question though :

Do you take insect macros, or was the setup more for other objects? Because if you do, do you then take the camera off the rail for pictures of moving insects? I have just tried to take a picture of a spider on a window sill, and in the 15 minutes i spent it must have traversed a good 6-10feet Luckily it was just traversing in circles. What would you do in this situation?

I am trying to find a good setup , equipment and accessories for insect macro...

Cheers!

10-02-2009, 05:32 PM   #9
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I'm by far from a macro expert myself, but I usually walk around the yard with that setup, and find some bug just sitting on a plant, and work from there. It's also good for flowers, but bugs that are on the go, it's not so handy. I've been successful with handheld, but try to make sure I can brace myself, of it's a right off.
10-03-2009, 12:15 AM   #10
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Ah thank you! I am not much for flowers, mostly bugs, so. But its good to hear it from you , so i know *not* to purchase one. I kept looking at bellows and macro rails and kept thinking i may need one.
Cheers!
10-03-2009, 01:21 AM   #11
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I'm surprised that noone's mentioned flash.

A good flash setup makes life much much easier.

- At macro distance, DOF is very thin. You will need to close down the aperture a lot for decent DOF. F/16 - F/32 are not uncommon. Unless you're shooting in bright sunlight, shutter speed will be low. With a flash, you can shoot at sync speed (typically 1/180), or even faster if your flash/camera supports high speed sync.

- At large magnification, movements of the object (e.g. due to wind) are greatly magnified. VR doesn't help in this case. You need hight shutter speed.

It's great if you can invest in a flash that supports P-TTL and/or high speed sync. If that's not possible, get a flash that has variable manual output.

You will need some sort of off-camera flash setup.
10-03-2009, 05:05 AM   #12
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thanks It may be because i opened a question thread on lighting problems i had just the day before in this forum

But while we are here...what is VR? I am going to have to research P-TTL as well...
10-04-2009, 02:02 PM   #13
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QuoteOriginally posted by D4rknezz Quote
Thanks for that image! Now i see how things are put together.

Question though :

Do you take insect macros, or was the setup more for other objects? Because if you do, do you then take the camera off the rail for pictures of moving insects? I have just tried to take a picture of a spider on a window sill, and in the 15 minutes i spent it must have traversed a good 6-10feet Luckily it was just traversing in circles. What would you do in this situation?

I am trying to find a good setup , equipment and accessories for insect macro...

Cheers!
It is kind of hard to take photos of moving insects..more so those that move fast.
One trick is to find a way to stop them on their tracks or slow them down a bit.
I have read somewhere that you can spray them with cold water as it slows them down.
Gently blowing on a spider also causes them to go to a kind of temporary "sleep" state.
Another trick is if you know where they are going, then try to focus far to where you will expect them to go and snap at the predetermined focus area..more like trap focus but you do the snapping.
I use Raynox DCR-250 for some of my macro shots as it is easier to put on and take off.
10-04-2009, 02:04 PM   #14
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QuoteOriginally posted by D4rknezz Quote
thanks It may be because i opened a question thread on lighting problems i had just the day before in this forum

But while we are here...what is VR? I am going to have to research P-TTL as well...
VR if I am not mistaken is the "SR" (Shake Reduction) for Pentax as "VR" (Vibration Reduction) is for Nikon and "IS" (Image Stabilization) is for Canon.
10-05-2009, 01:31 PM   #15
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Thanks! that cleared it up for me

QuoteOriginally posted by GerryL Quote
VR if I am not mistaken is the "SR" (Shake Reduction) for Pentax as "VR" (Vibration Reduction) is for Nikon and "IS" (Image Stabilization) is for Canon.
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