Familiar with close-up lenses?

[jolefler]

Although the process I'm using involves copying 35mm negs with a digicam instead of a scanner, this is really a question about the optics, not a hybrid process.

I use a +2 close up lens in front of the digicam lens, which fills the frame. When I copy the negs I get a fairly usable image, but the sharpness deteriorates horribly from the center to the edges...especially the 36mm axis.

I'm assuming that's due to the close-up lens degrading the image toward the edges. Would the use of a step-up ring (say 52-67mm) and a larger +2 close-up lens help the situation? Thanks!

Jo

 

[Nicholas Lindan]

Try really stopping down the lens on the digicam. You may also want to focus about 1/3 from the center or so: it is a trade off between center and edge sharpness. The results will never be that great, though close up lenses can be sharp they are not flat-field - it is the nature of using closeup lenses and there isn't much you can do about it. Stopping down increases the depth of field to allow you to get more of the slide in focus.

 

[Konical]

Good Morning, Jo,

Generally speaking, it's a good idea to use small f-stops in conjunction with auxiliary close-up lenses. Are you sure that you have everything locked up tightly in your copying set-up? A little vibration is magnified greatly in 1:1 situations, especially if relatively long exposures are required.

Konical

 

[jolefler]

G' morning! I'm pretty sure everything is tight. I always use the self timer to trigger the shutter on a 2-4 second delay; since it's all electronic, I doubt vibration is an issue.

The aperature is an issue, though. The lens only stops down to f8, a major limitation, though that's the aperature I always use. A trade off in focus location may help, though...thanks for that! Perhaps I can experiment with bending the neg slightly to accomodate focus; no wait... I get a good, square rectangle around the edges now, curving the neg will mess that up.

 

[Q.G.]

This is a "there is no free lunch" thingy.
Close up lenses typically have terrible aberrations, which you can't conjure away by bending the film or shifting focus.
You will get far better results using extension tubes (even with a standard lens). A special macro lens would be even better.
But they cost...

 

[n5jrn]

The lens only stops down to f8, a major limitation...

Not on a compact digicam with a tiny sensor (and thus a really short lens focal length). F/8 is a *really* tiny hole (generally already at the point where diffraction is starting to degrade image quality) at the wide end of a digicam zoom. It's smaller than f/32 on a 50mm normal lens on a 35mm SLR, in fact (assuming an actual focal length of 10mm or less on the digicam).

 

[geoferrell]

I've used a Cokin P Adapter with a #2 closeup filter on a MF 80mm lens and gotten good results. I think macro lenses probably do better, especially for more depth of field.

 

[archphoto]

Sorry Geoferrell, to correct you: depth of field is determend by the focal length, the distance to the object and the aperture.
Macro lenses perform better because they are designed esp. for close-ups.

Jolefler: save those slides for the time being untill a scanner comes up.

Peter

 

[jolefler]

Thanks folks!

For now, I get very passable results by wet printing a 5x7, then shooting that with the same digicam (no C.U. filter needed) on a copy stand.

Most of my APUG portfolio are copy stand digi shots of 8x10 prints. I'm inclined to just take a pass on neg scanning/copying.....there's also the side benefit of seeing my printing improving with all the practice!...AND, I'm helping create a demand for silver gel paper!

Jo