Focusing with macro lenses ...

[indianadinos]

Hi all,

I need an advice about macro lenses ...
I have noticed that when focusing with "standard" lenses, i'm quite fast and since i mounted a Katzeye focusing screen rarely miss the focus on an image.
My issue is that this is no longer true when using macro lenses ...
It is not an issue about the barrel thread length, but i find a bit difficult to get the proper focus on a subject with a macro lens rather than with a normal lens ...

As an example, if i use my Pentax 105/2.8, i will focus and see the subject in focus in the viewfinder.
If i use my Phoenix 100 or my Kiron 105, it takes a bit longer to spot the right focus in the viewfinder ... It is quite a kind of "feeling" about the right focus (sorry, don't know how to explain this in english), but, again, not an issue with the longer focusing thread of the barrel ...

Is this the nominal behavior, or i have an issue with my eyes ? Before you ask, i have verified the diopter corrector of the viewfinder against a white wall and without a lens ...

All the advices are welcome ...

Thanks in advance for your replies (and especially for explanations, if you have some).

Cheers

[poilu]

I am not sure to understand the question but it is a fact that focusing is more easy with a better lens
With good lens, you have 1 point of focus and you know when you have it
with not so good lens you have to move barrel many times and guess the better position

[hinnerker]

[patrickh]

I think that the longer the "throw" the easier it is. When focusing takes a lot of turns it is easier to get it right when in macro. Most macro specialist lenses have this long throw



patrickh

PS the rest of the advice is very good

[mo]

[cooltouch]

I have noticed with my macro lenses that the longer throw results in an image that doesn't "pop" into focus the way it does with a normal lens. Thus, I really have to observe closely for that maximum point of sharpness. Also, given that I'm often working at higher magnifications with macro lenses, this means the depth-of-field is next to nothing, so any backward-or-forward movement I make can affect the image. For both these reasons, I prefer not to shoot with my macro lenses wide open, and a tripod is always a good idea. I consider f/8 to be a minimum useful aperture with them.

[scsambrook]

[Photomac]

It seems likely that the difficulty is due to a combination of several of the factors mentioned already:

- when taking macro the lens is at or near it's closest focus distance, so DoF is as small as it will ever be
- the long throw allows very fine adjustment by hand to accommodate the DoF
- since the focus adjustment is so fine (per degree of rotation of the barrel) the change from in focus to truly out of focus is gradual
- the human eye-brain function is poor at detecting absolute sharpness, and responds better to change.

This would explain why macro focusing doesn't 'snap' the way normal lenses do.

In summary, a long throw helix is very good physically for minute adjustment, and very bad perceptually for us humans to tell when it's right.

Regards

Angus

[rick_oleson]

Unless you're shooting on a tripod (which only works with VERY stationary subjects), I don't use the focus ring for focus adjustment in macro work: I set the focus ring according to the general distance/magnification that I am working at, and then move myself forward and back to get into focus on the specific point I'm after. This is faster, you can make the image snap in and out as fast or as slow as you want, and release the shutter at the instant that you see it's right.

I find fine micrometer-like focus adjustments very difficult to work with ... I had a 50mm Schneider Xenon that took over 300 degrees of barrel rotation to get to minimum focus, it was a fine lens but I felt I could never find the focus point with it. Replaced it with a Zeiss Biotar that is probably not as good a lens but it works much better for me.

[Orio]

I personally think (very personal opinion) that for macro focusing, nothing beats a good bellows trail.

-

[sichko]

[Dream Merchant]

A lot of good info, especially about the lens focusing throw and minute movement throwing focus out at higher magnifications! I learned a lot in this thread!

OP, have you tried a rough ground focusing screen? Basically, it makes the viewfinder images 'SNAP' in and out of focus much faster than a normally ground screen. I'm not familiar with the Pentax cameras, so you might have to look around different sources a bit. In Canon DSLRs, this screen goes by the post-fix of 's' (xx-s screen). Bear in mind, the rougher the grind n the screen, the darker the VF image. I usually can easily focus using this screen and lenses up to about f/4 or so.

[poilu]

you have to check for backfocus
if you focus on eyes and get a result like mine, you probably need to shim your screen

backfocus sample

[patrickh]

Bellows is definitely the way to go though for precision. Some also like the focusing helicoids for rigidity.


patrickh

[Dream Merchant]

Would a well-made macro focusing rail work as well, if higher magnifications are not needed?

[indianadinos]

Well, a lot of really useful infos here ...

[cooltouch]

[Bruce]

[Screamin Scott]

[quote="cooltouch"]

[cooltouch]

[DSG]

I often find it best not to use a tripod for my macros and I focus by moving then lens closer to or further from the subject whilst looking through the viewfinder...Here's my handheld setup:

[patrickh]

And you pump iron on a regular basis?

patrickh

BTW I know you get superb results with that

[cooltouch]

Sorry, but I can't help but find it a bit ironic that your "hand held setup" is mounted to what looks like a pretty stout tripod.

What is that lens combo, by the way? A long Nikkor macro with a stack of extension tubes or something?

Also, I can't tell from the photo how your Metz flash is mounted to this hand-held setup -- what sort of bracket are you using?

Cool, it looks like your Sigma has a PC connector. Wish my Canon did. I'm guessing that's an older Metz, so you're not worried about trigger voltage, eh?

[ChrisLilley]

[DSG]