Thread: Infinite focus - explaination and options
 

Hi,

I recently got a GH2 and love it. My first lens was the Olympus 45mm 1.8. I love it for the quality and shallow dof.

I will shoot mainly video, and their will be times when I don't want to worry about the shallow dof and have most/all of the frame in focus.

I've been researching non-stop for a week, but I must admit that I don't yet fully understand what to look for in an lens to achieve this. I know that setting a higher aperture will increase the dof, but I'm not sure how far you can take it (does a better light rating offer wider dof option I'm guessing) and what other factors affect it.

I'd really appreciate a more detailed explanation and some suggestions. I'm looking at the 14mm or 20mm Panasonic pancakes as a possible next option, along with some of the more expensive options for better low light performance.

Thanks.

Re: Thread: Infinite focus - explaination and options
 

There's little to say except shoot at f8 or above. Outdoors during the day is easy to achieve this, indoors not so easy. You can shoot at lower aperture numbers with the 20mm if the subjects are a distance away from the camera but it will be hard to be sure. Here is where a video camera outshines a DSLR.

Re: Thread: Infinite focus - explaination and options
 

Luckily the m43 system has a slight edge in this department vs. the S35 and FF bretheren.

For deeper focus, stop down, go wide, and increase the working distance. It's that simple. The wider the lens, the less you'll have to stop down and back up. Any of the wide lenses can manage this. Longer lenses have a tougher time of it.

On the extreme end of things, a pinhole lens (like the Pinwide or a homemade body cap pinhole) will put absolutely EVERYTHING in focus - from the dust on your sensor to the farthest star. They do make proper exposure somewhat of a challenge, though ;)

Re: Thread: Infinite focus - explaination and options
 

Thanks for the feedback. It's interesting. I have the 45mm Olympus and just bought the 20mm Panasonic. With both, I first setup a scene with a person maybe 15 foot from the camera with a high aperture setting which blew out the background. I then took the aperture as low as possible (in steps) and the bokek blurred background wasn't affected noticeably.

Both times this was indoors with a fair amount of sunlight. I'm sure outside it would be somewhat different, but the results were so far off that I wonder if I could even get what I'm looking for indoors with a high quality 14mm.

Obviously, this is where video cams shine.

Re: Thread: Infinite focus - explaination and options
 

Indoors I've found both the 20mm and 14mm to be excellent performers. If you're after deeper DOF (deeper zone of acceptable sharpness) you're going to need more exposure (light) indoors. Two ways to do this:

Add light with lighting equipment (best quality), or raise the ISO. There will be limits to how far you can raise it without getting potentially objectionable noise.

When I work indoors and can't (or don't want to) use extra lighting, I try to use the 14mm because even at maximum aperture (f2.5) the wide angle gets me a rather deep focus zone. Working distance with that lens affects the zone of focus also.

Outdoors you're going to run into another problem. Too much light and without ND filtration you may find yourself having to use an aperture that's too small. Two problem areas with this:

Your zone of focus may be way too deep for what your want to show, and at minimum or near minimum apertures you begin to run into the "diffraction" effect. This is where the image forming rays begin to "scatter" and "diffuse" to some extent and don't travel in the same straight lines they do at larger apertures.

The result is the appearance of some diffusion in the image rendering it softer than normal. Edge outlines won't look as sharp as they should and there may be a slight loss of contrast. I got "bit" by this very badly when I forgot to reset my ISO from where I had it the night before. The images took a lot of work in PhotoShop (unsharp mask and contrast adjustment) to make them look normal.

Solution: ND filters. I keep 0.6ND, 0.9ND, and 1.2ND in the bag (2 stop reduction, 3 stops, and 4 stops respectively). I can't use a hood on the 14mm without some vignetting, I have to use a wide angle hood on the 20mm (it's a "wide" normal field of view), and a deep hood on the 45mm.

I do avoid the use of variable ND filters as Lumix lenses seem to be very susceptible to internal reflections from filters and the variables are 2 pieces of glass adding FOUR potentially reflective surfaces.

Re: Thread: Infinite focus - explaination and options
 

Bruce (or anyone else, for that matter),

Care to recommend a brand of ND filters you like for the GH2? I'm an amateur and see many brands available. I don't wish to "experiment" and buy one at random.

D

Re: Thread: Infinite focus - explaination and options
 

Dennis,

I've been ordering Tiffen from B&H. Originally I thought that was an "OK" brand but after reading that Shane Hurlbut likes Tiffen filters and trusts them for quality, it looks like I probably made a right choice.

You can spend more and likely get better quality, but I've been happy with the Tiffen ND's. Now for UV (which I don't try to use with Lumix lenses) I go for the HMC, SMC, or Hoya Digital.

Since I use Panasonic Lumix lenses, the Pan/Leica 25mm f1.4, and the Oly 45mm f1.8; I use 46-52mm stepup rings on the Lumix "pancakes" and the Pan/Leica 25mm, a 37-52mm stepup ring on the Oly 45mm and get my filters in 52mm size. The Lumix 45-200 and the 14-42mm "kit" lens both have 52mm filter threads so the one size, 52mm, fits all of my lenses.

One thing very important when using filters on these lenses is to insure you have adequate "shading" from stray light with a decently "deep" lens hood. The 45-200, 14-42mm "kit" lens, and the Pan Leica 25mm come with workable effective hoods, but the 14mm and 20mm are problematic. The 20mm is wide enough that standard hoods vignette, and the only hood I've seen that doesn't vignette on the 14mm f2.5 is "pathetic" for effective shading.

My solution for the 20mm is the CineTactics MatteBlox DV with the oversize French Flag (cinetactics Home Page). It's "HUGE" but works and it should also work with the 14mm (I haven't had a chance to test it yet with the 14). Two images attached showing it on the Lumix 20mm.