OK, I asked this before,but didn't get a real answer (in another forum). If the "crop factor" of my camera is 1.5, and I am using a lens that reproduces at 1:4, is it so that my magnification will actually be better than 1:4. I think it figured to be only slightly less, but someone told me this wasn't so.

Second question, most of my closeup stuff is done with a 70-210 with a ratio of 1:4, will a 28mm ext. tube make enough difference to justify the $89? I really like the macro stuff, but don't want to add another lens. Here's an example of what I get from this lens now.

Wow Wow :)

Payn, first question about the crop factor - think of it this way: If your lens produces 1/4 life size image at the film plane (sorry, imaging sensor plane :p ), that does NOT change regardless of the "crop factor". Remember, magnification is measured at the film plane so if you hold your CCD/CMOS sensor with image on it up against the subject, the image there would be 1/4 the actual size. The crop factor works its way in if you "stretched" the digital image to that of the full-frame 35mm size. Thus, the effect of this stretch on paper or screen gives the illusion of a more magnified image. It's really just an automatic crop that the camera does. Does that make sense?

As for your second question, for those images unless you wanted more magnification you don't need the tubes. Great images btw. Only if you find yourself maxing out on the current magnification should you consider buying anything else.

OOPS, Loupey made a boo boo :wink:

Your lens focuses to 1:4 on a 24x36mm frame(35mm film). the crop factor will magnify that ratio because your camera's sensor is smaller. The angle of view remains the same, but the appearance of closeness changes from the smaller sensor.

Think of it this way.... take a 1:4 image on film and crop it down to the the area of coverage of your camera's sensor(whatever that is) and you now have an image that is CLOSER to life size.

Hey I'll leave it to the tech guys to answer the question. All I know is I like getting close and anything that I can get that will get me closer I'm all for it. Love my new auto tubes with the 105 macro and with the 80-200. I also like the images you have been producing with your setup. These two are great.

Well, yes and no. Let's try it graphically.

Your lens produces an image circle inside your camera. The blue frame represents the corresponding capture from a full-frame sensor/film. The red frame represents the capture from a smaller-than-full-frame sensor (1.3, 1.5, 1.6, etc.).

Note that, at the focal plane, the REAL magnification produced by the lens has not changed. A 1:4 ratio at the focal plane remains 1:4.

What will change is the APPARENT magnification when you print (say an 8"x12") an uncropped image from both sensors. Since the red frame captured a smaller area, it will appear that the magnification has been increased when comparing output reproduced to the SAME print size.

Note that all the while, the lens magnification (image circle) at the focal plane remained unchanged regardless of the SLR used. "Magnification" is measured at the film/sensor, not print size. I can take a lens that produces 1:2 (half life size), and make an enlargement print that now has an image 10x life size. The lens still produces 1:2. Not 10x.

Right'o

After reading and rereading the original, I think I mistook what you were saying. You seem to have the right wording for what I was trying to say.

The bottom line to me is.... An APS sized sensor will capture a tighter (closer to life size) image with said lens compared to a full frame camera. The lens doesn't focus closer, nor does the angle of view change.

If this is an example of what you are getting now! boy stick with it!

Stunning pictures, colours, detail and sharp. Do you do any manipulation work with your images?

I have a VERY basic workflow, usually I boost my shadows a little, and just a slight touch of saturation. Sometimes, though not often, a little bit of sharpening.