300mm Apo-Ronar fuzzy image

[Geoffrey moore]

I just mounted an in barrel 300mm f/9 Apo-Ronar for use with my 4x5 camera. My goal was to achieve infinite depth of field at 1:1 or greater. I used this lens because the iris on this lens stopped down to f/260. The result was a completely fuzzy image. Is this normal for these lenses? If so, are there any other lenses anyone knows of I can use to achieve my goal? BTW, the image was great wide open.

[Nick_3536]

At F/260 I'm not surprised things got fuzzy. My math maybe off but you can't get more then 6 or 7 lp/mm at F/260.

[Hiro]

Isn't it a simple case of diffraction? f260 on 4x5 is equivalent to f64 on 35mm and f128 on 6x6. It's way small. I think the small aperture was meant for repro work using 16x20 or larger films (or whatever on the other side of the lens).

[N Dhananjay]

It's actually even worse than that. f/260 at 1:1 macro magnification becomes an effective f/520. That is essentially pinhole photography and you are definitely diffraction limited. You will have a lot of depth of field but resolution will be pretty poor. So everything will be equally in focus (or out of focus, depending on your point of view). Macro work is hard for exactly that reason. Thinking of compositions that will reduce your DOF demands is the best way to proceed here.

In some ways, LF is particularly hard. Keep in mind that 1:1 in 35 mm is an approximately 1 square inch area (a small flower, for e.g.). The same 1:1 in 4X5 is a 20 square inch area (a small bed of flowers) which most of us do not intuitively think of as macro work - we tend to think of macro work as being very small things. So, if you try to do the usual kind of macro work (a small flower), you are effectively looking at something like 3X or so magnification and your effective aperture is becoming very problematic. When doing macro work in LF, you really need to rethink your ideas of what macro compositions are. But when it works, the smooth tonalities are to die for.

Cheers, DJ

[Paul Fitzgerald]

Hi there,

You could try a 75 - 105mm enlarger lens reversed and/or a precision drilled waterhouse stop. Any adjustable iris has a very jagged edge when stopped down making the diffaction problem worse.

You could get in touch with Panaflex for one of their infinite depth of field lenses but they will not sell them (and they are patented)

Good luck with the impossible.

[Bob Salomon]

You are deeply into diffraction. That lens was made to be used at f16 to 22 only.

[Tom Keenan]

Bob:
I'm glad you checked in. Since this lens should be used at f16 to f22, why have markings all the way to f260? Is there some historical significance? Process Camera application that used such small stops?
Thanks.

[Bob Salomon]

Tom,

If you had bought a lens that only had markings for optimal aperture then people would want to know why there was so much movement before and beyond the optimal settings.

[Joseph O'Neil]

I have three process lenses, all F9, different sizes, and like Bob says, I use them all around F22 on average, although my Apo Artar seems to work great at F32. Still, F32 is waaay far off from f260. Try F16 to F32, see how it works
joe

[Robert McClure]

Not to minimize the importance of Mr. Moore's original question, but ...

I noticed Hiro's comments, for example. Can Hiro or anyone tell me why repro lenses often stop down so far - to f128/f260, for example? Is it simply for the fact that when shooting line-copy onto 16x20 film, normal diffraction at these pinhole apertures doesn't become an issue? I would think that on a litho camera one would shoot at the "best" aperture all the time. With lighting constant and subject (line copy, for example) motionless - what in the world would you need to stop down so far for? I am puzzled!!! Did this allow lithographers to imagine they had more "control" or what?

Thanks!

[N Dhananjay]

Just a guess. A process technician would leave the lens at f/22 where s/he would get the best performance out of the lens - keep in mind DOF requirements for flat field work (which is what these lenses were originally intended for) are minimal. However, since the lens is faster (i.e., can be opened up further, say to f/9), it makes sense to have an iris and have a brighter image for focusing. And once one has taken the trouble to put in an iris, you might as well go ahead and mark the f-stops down as far as you want.

Incientally, the suggestion to use a shorter focal length lens (like an enlarging lens or a dedicated macro lens) is a good one. The shorter focal length will give you better DOF and since the bellows extension is significant, coverage is typically unlikely to be an issue.

Cheers, DJ

[Dan Fromm]

DJ wrote "... the suggestion to use a shorter focal length lens (like an enlarging lens or a dedicated macro lens) is a good one. The shorter focal length will give you better DOF ..."

Have you done the calculations? I have, and close up (at magnifications >= 1:10) depth of field is controlled by aperture (the f/number, not its diameter) and magnification. Focal length has no effect.

I wish there were a magic way to get more DOF when working closeup, but scanning is impractical in most situations.

There IS a situation where using the shorter lens will gain DOF, but not in macro and its utility is limited. Suppose that the shorter lens gives the desired image size when the subject at least half the lens' hyperfocal distance away. Then focusing the lens at the hyperfocal distance will bring the subject into satisfactory focus and DOF will extend from h/2 to infinity. Move back to get the same image with the longer lens and focusing it at its hyperfocal distance won't give as much DOF, also may not bring the subject into adequate focus. If we focus at the subject to get best sharpness in the subject's plane, then if the subject is farther away than the shorter lens' hyperfocal distance and inside the longer ones' hyperfocal length gives much the same result.

[Hiro]

Robert,

Well, I don’t know... The format equivalent of f-numbers is a reference to Stroebel’s View Camera Technique, but he must have meant conventional photography when writing “objectionable loss of definition.” On a process camera, using the optimal aperture would be a sensible thing to do as you say. f250 would be of any practical use only if the lens were to be used for conventional photography with ultra-large films. I didn’t think about the distinction carefully. Would lens manufacturers have designed the lenses for such possibilities? Or was it just a customary practice as Bob Salomon explains?

[N Dhananjay]

Whoops! Dan is correct - I forgot we were talking about the macro region. And focal length does have no effect - DOF is only dependent on magnification and f-stop. Thanks for catching that and correcting it.

But I guess shorter focal lengths still have utility since the demands on bellows extension is lower. Cheers, DJ

[Geoffrey moore]

Thank you everyone for your responses. I very much appreciate your insights.