Tamron 90mm SP f2.5 Macro Lens - Adaptall

I have the opportunity to purchase this lens for my Samsung GX10 which would give me a 1:2 macro facility. I am new to Tamron Adaptall lenses. There is also an extension tube that would result in 1:1 My question is though .... since the Samsung (as also the Pentax K10D) has a factor of x1.5 ... do you really need the extension tube to get you up to 1:1? Would the basic lens and the x1.5 factor not bring me up close to true 1:1 anyway? Am I missing something? Comments appreciated.

No difference - on 35mm, the camera would fill the frame with a 35mm bug, but this time, the camera fills the frame with a 24.5mm bug. Its still 1:1, just cropped.

As I said, I'm new to Tamron lenses ... could you clarify this for me. Do i need the extension tube to get 1:1 macro?

that depends on what you want.

The Macro ratio notation, 1:2, 1:1 and so on, refers to image size on film. Therefore, strictly speaking, the crop factor has no influence on macro ratios.

If you're more interested in how close you need to get to fill the frame with a given beastie, then of course it's a different story.

I have the Tamron you mention, and for general close ups of butterflies and the like it is superb. I have only used my 2x converter to get 1:1 2 or 3 times.


If you're buying the lens for full on true macro it's best to have either the extension tube or the matched 2x converter, if its really just for close ups of little things then you'll probably be fine without.

I guess like most things in life ... I won't really know exactly what i want until I try it. I want to photograph beasties for sure, butterflies etc. Anyone else have the extension tube or 2x convertor and hardly use it? (If this is the general case, then I will just buy the lens and forget about the extension tube or the 2x convertor). Comments appreciated.

My understanding of 1:1 macro is that an object of, say, 20 mm size will fill 20 mm of the active sensor area. Whether this is an APS-C digital sensor or a 35 mm film frame does not really matter.

Maybe the experts can confirm if this is a correct definition. What say, Clarky?

Yes Terry I believe so too, although i'm not Clarky
The size of the sensor can not change the characteristics of a lens.
Because that the sensor is smaller it captured less from the projected image. If you crop on your pc things doesn't change of your lens either, the object always stays 10 pixels long for example?
a 100mm will also be a 100mm no matter on what the size of the sensor is.

it's really simple to explain the 1:1 thing
We take a bug 1mm long with a 1:1 lens will be projected as 1mm long bug on the sensor or film, a 1:2 lens will project that bug as a 0,5mm long bug on the sensor or film. You can change the size of the sensor as much as you want but it won't change the lens so the bugs stays the same as describe here above.

Do you concur?

Hi. Thanks to everyone for your comments. I purchased the Tamron plus the extension and mount adapter on eBay last night for £78 (fully boxed and instructions). Good price? Can't wait to try it.

Yup, that is a good price. Have fun!

Best wishes, Kris.

Stefan,

I agree with your bug example. However, using a photo processing program (e.g. PSE6) you can resample the picture to any pixel size, so that example just adds to confusion.

The main thing is that true 1:1 macro means that the object is projected at life size onto the sensor/film frame.

Ironwill,
Congratulations on your new lens. Look forward to see samples in the forum.

I don't begin to understand all the mathamatics of it all and don't consider myself an expert on the subject.

My understanding of 1.1 is exactly as Stefan described it.

Personally I would have purchased the extension tube with it. After using it for a while you will be looking to get even more magnification and adding further tubes to it.

Have fun with it and post some pics.

Good shooting with the lens Ironwill and thank you for the acknowledgement Steve & Terry, I wasn't trully sure myself.

Hi

Which is best for 1:1 macro work with the Adaptall 90mm SP f2.5 (52B), extension tube or 2x Teleconverter?

Does any one have an Adaptall extension tube that is surplus to requirements?

Simon

As far as I know, the teleconverter doubles the focal length, but does nothing to your closest focus distance.

The extension tube, however, reduces the focus distance, providing macro.

The matched teleconverter will give 1:1 macro with the lens which is 1:2 "out of the box"
I would presume though that it will add a couple of stops.