My 1st stacks

qanunji · Post by **qanunji** » Mon May 30, 2011 6:33 am

Hello everyone,

here are my 1st 2 stacks.
I can't afford a macro lens now, so I'm just stacking lenses.
I got some pretty results using ZS, But i need to polish my retouching, as well as cleaning the specimens.

rjlittlefield · Post by **rjlittlefield** » Mon Jun 06, 2011 10:30 am

First stacks are always both encouraging and frustrating. These look like a promising start. What lenses are you putting together, and how are you stopping them down?

--Rik

qanunji · Post by **qanunji** » Mon Jun 06, 2011 1:52 pm

Thanks Rik.

I'm coupling a Canon 50 1.8 over Canon 250.

stopping down and fine focusing is via DSLR Remote.

rjlittlefield · Post by **rjlittlefield** » Mon Jun 06, 2011 2:27 pm

OK, then you're probably losing some quality because DSLR Remote is stopping down the rear lens. At this magnification you'll probably get a lot better image quality by stopping down the front lens. See "FAQ: Stopping Down a Lens Combo" for discussion and illustration of how much it can matter.

With newer Canon lenses, the apertures are controlled electrically from the camera. This makes stopping down the front lens awkward, but not impossible.

The trick is put the front lens on the camera body, turn on the camera, set the desired aperture, hold down DOF preview to physically stop down the lens, then remove the lens from the camera while continuing to hold down DOF preview. This cuts power to the lens while it is stopped down, and it stays in the stopped-down position.

Then you put the lenses back the way you want to use them, and do your actual shooting with the rear lens wide open so the two apertures don't fight with each other and cause vignetting.

I suggest stopping the front lens to f/4 as a first attempt. Then if you like, you can try also at f/2.8 and f/5.6 to see if either of those is any sharper.

--Rik

rjlittlefield · Post by **rjlittlefield** » Mon Jun 06, 2011 2:30 pm

By the way, the quick calculations here are that

magnification = rear_lens_focal_length / front_lens_focal_length

effective f-number = front_lens_setting * (magnification+1)

So with the 50 mm in front of 250 mm, and the front lens stopped to f/4, you're looking at 5X magnification (because 5=250/50) and effective f-number of f/24 (because 24=4*(5+1)).

--Rik

qanunji · Post by **qanunji** » Mon Jun 06, 2011 9:48 pm

thanks!