Hard "edge" on Highlights with Soft Focus

[alanbutler57]

I've been playing with the Mamiya Sekor 150SF on my RB and have an adapter to use it on 4x5 at some point. My question is about how to avoid a hard "edge" on the spread out highlights. In the example below there is a "ghost" around the tail and sleeve shirt tail of the male dancer. Would over exposing the image have made this edge softer? Sorry I don't have a 4x5 shot with this lens yet.

I should add the lens is wide open here, with no diffusion disc.

Thanks in advance!

[Jac@stafford.net]

I've been playing with the Mamiya Sekor 150SF on my RB and have an adapter to use it on 4x5 at some point.

Will the lens cover 4x5?

[alanbutler57]

Will the lens cover 4x5?

I've tried it a couple of times, unfortunately, this is the only one that I hit focus on. Visually, yes it covers with some room for movement, as do the 90 and 250 that I've looked at. A bag bellows is required. I haven't checked infinity (not my interest), but the standards would have to be very tightly pressed together.

The first image below is the 150SF (I didn't use this earlier in the thread as there isn't a white item throwing a halo) it is lit with a single strobe in an "AdMagic" Fresnel housing, the second (cropped for content) is the 250 on 4x5:





Here's a picture of the Linhof front standard with the front of a junk RB grafted to it (via carved hardwood spacer and jb weld) with cocking/release lever attached underneath:



Certainly not as versatile as using traditional LF lenses. But, it allows me to use one set of lenses on two camera systems and play with a soft focus lens, with shutter for around $100 plus the cost of the junk RB (~$60 or $70 I think).

[Jac@stafford.net]

Great information (and very attractive images.) Thank you, Alan.
I have no help for your original question.

[Mark Sawyer]

I've been playing with the Mamiya Sekor 150SF on my RB and have an adapter to use it on 4x5 at some point. My question is about how to avoid a hard "edge" on the spread out highlights. In the example below there is a "ghost" around the tail and sleeve shirt tail of the male dancer. Would over exposing the image have made this edge softer? Sorry I don't have a 4x5 shot with this lens yet.

I should add the lens is wide open here, with no diffusion disc.

For better or worse, that's the signature of that particular lens. In it's particular construction, the spherical aberration has a harder break than most others I've seen. You can try it at slightly smaller stops; it's hard to predict how that will change the more defined break, (could be softer or harder), but the halo will be less pronounced as you cut off the outer edges of the light path where all the aberration is going on.

Other than that, you could try variations on an Imagon-like stop to get some but not all of the halo,, but on that lens, the disk should be inside the lens where the regular aperture is. Or avoid bright highlights and harsh lighting.

On an only semi-related note, it's interesting to see how much the spherical aberration spread the depth of field in the first image. Fairly deep for a wide-open 150mm on a 4x5! Did you use any tilt?

[alanbutler57]

Hi Mark and thanks,
The very first image with the depth of field, was, in fact, shot with the RB67, not 4x5, in the OP I stated I didn't have an image with the 150 on the 4x5, but then remembered and found the young lady I shot from Model Mayhem with the Fresnel. I suspected this may be an attribute of the lens, which may explain why some people really don't care for it. I could have softened the edge in Photoshop I suppose, but was just curious as I've only used the lens for about a dozen shots or so.

The only way to get much in the way of tilt etc. from the hybrid RB/4x5 rig is to work close in, say within 12 feet or so, otherwise the front and rear standards are too close together. It should be great for macro though, the fellow who posted this idea originally (name escapes me) over at Photocamel primarily used the RB/4x5 combo for macro.

[Mark Sawyer]

My apologies for not reading more attentively, I got too hung up looking at the photos! If you do decide to use the lens very much on 4x5, perhaps a recessed lensboard might help with the movements issue?

[jp]

Usually stopping down a little kills that real quick. It can be moderated with less contrasty lighting too. It's OK to have that glow/edge (perhaps in a little more moderation) when there is not major detail in the scene. Bigger areas of light and dark.

If you want a cheap 4x5 lens without much of this, the Fuji ones do. I'm not crazy about them as I like some of that glow. A Verito or Wollaston meniscus are my choices.

[Jim Andrada]

Just as an example, this was also taken with the Mamiya 150 SF at either (I forget which) f/5.6 or f/8. In this case I think it puts a nice glow on the rims of the cactus

Potted Cholla by Kirigakuresaizoh, on Flickr

[alanbutler57]

My apologies for not reading more attentively, I got too hung up looking at the photos! If you do decide to use the lens very much on 4x5, perhaps a recessed lensboard might help with the movements issue?

I'd thought about that after the fact and almost listed it as a recommendation to those who want to build one. Two considerations though, first the recessed area of the board must be large enough for the RB67 front standard to fit into, additionally, the cocking and release "trigger" would have to be "L" shaped with a leg protruding parallel to the lens so as to make it accessible.

Another point on the "trigger", my brother has very nice wood and metal shops and loves this sort of thing, so he took an piece of steel he had laying around, cut and bent it. We did not give thought ahead of time to weight. As it turns out, this one is pretty much pefect, any heavier and the shutter would not stay cocked as the weight of the trigger would move it into the "release" position. But, by being relatively heavy, it lessens the "trigger pull" which likely lessens shake imparted by the finger that touches it off.