Blur Radius vs Blur Falloff ~ APS-C ~ Ricoh Riconar 55mm f/2.8 at three apertures

Up to now I've been measuring things out of a Full Frame Sony.  As a spot-check I had a look at how things measured up on Sony APS-C. 

It's my hope that I've described things clearly enough that anyone can do this.  It takes no special equipment.  No fancy anything.  Just a few photos with understanding of how/where to measure blur.  The method was described in 1906 in Biblioteque de la Revue de Photographie -  L. de Pulligny - C. Puyo "Objectifs d'Artiste Practique et Theorie des Objectifs et Teleobjectifs Anachromatique" found at the Biblioteque national de France (BnF).

Now, to revisit a cheap Ricoh Riconar 55mm f/2.8 four element four group strange design first element focusing lens, the optic is very flexible.  Wide open it's soft.  Stopped down it is very well-corrected across the field.  It's very easy to use first and second element separation to induce and control softness and the aperture to define sharpness.  This is the lens where I learned about first element focusers.  This is a "do it all" kind of lens.

Here's how to read the following graphs. Please keep in mind that these are for Full Frame digital.  APS-C is slightly different from Full Frame, as we will now see.  I checked lens/filter combinations for three aperture settings.

 

 

 

Comments ~

As with the Ricoh Auto-Rikenon 50mm f/2.8, there are (at least) two things I note.

First, Blur Falloff tracks between Full Frame and APS-C, but, as expected, Blur Radius does not.  APS-C measures as larger than Full Frame.  The Blur Radius difference is easily calculated based on the physical sensor size differences and is verified in practice (direct measurement). 

Second, Blur Radius vs Blur Falloff slide left as the aperture is stopped down.  This, too, is to be expected.  The scene sharpens up and the depth of field increases, thus reducing optical imperfections and soft filter contribution. 

This is fun.  Knowledge.  It can be useful. 

 

Blur Radius vs Blur Falloff ~ APS-C ~ Ricoh Auto-Rikenon 50mm f/2.8

I haven't said much about the importance of digital sensor size in my little look-see into soft focus lenses and filters.  I've been measuring everything up to this point using a Full Frame Sony.  As a spot-check I had a look at how things measured up on Sony APS-C. 

Returning to a pretty little Ricoh Auto-Rikenon 50mm f/2.8 four element three group tessar design first element focusing lens for a moment, I find the optic is sharp from wide open and is well-corrected across the field.  It's really difficult to use first and second element separation to induce and control softness in this one.  I believe it to be a Cosina re-badge as it appears to be found under any number of 3rd names.  If you can't afford a Carl Zeiss Jena Tessar 50mm f/2.8, try one of these.  It's simply brilliant for normal work.

Here's how to read the following graphs. Please keep in mind that these are for Full Frame digital.  APS-C is slightly different from Full Frame, as we will now see.

 

 

Comments ~

There are (at least) two things I note.

First, Blur Falloff tracks between Full Frame and APS-C, but, as expected, Blur Radius does not.  APS-C Blur Radii measure larger than Full Frame.  The radius difference is easily calculated based on the physical sensor size differences and is verified in practice (direct measurement). 

Second, Blur Radius vs Blur Falloff slide left on my graphs as the aperture is stopped down.  This, too, is to be expected.  The scene sharpens up and the depth of field increases, reducing optical imperfections and changes soft filter contribution. 

This lens is perhaps a little too well corrected for trying to match early Pictorialist era print softness. 

 

Blur Radius vs Blur Falloff ~ Steinheil Auto-Cassaron 50mm f/2.8

A friend pointed me to the Steinheil Auto-Cassaron 50mm f/2.8.  It's a Cooke triplet first element focusing 35mm SLR m42 mount lens and it's rather special.  It positively glows at all apertures and all subject distances.  These first element focusers can work magic by gently introducing optical imperfections as the first and second element distance changes.

Here's how to read the following graphs. Please keep in mind that these are for Full Frame digital.  APS-C is slightly different, as we may see in future posts.

 

 

Comments ~

The lens is soft overlaying sharpness.  At all apertures.  This seems to be Steinheil's design tendency.  

ISCO (the budget design house of Jos Schneider), Schacht, Roeschlein, Staeble, and of course Zeiss by comparison, are contrastier than Steinheil from wide open.

The Steinheil 45mm f/2.8 Cassarit and 135mm f/4.5 Cassar all show similar levels of softness that veil over a distinct sharpness.  Because of the rendition I feel Steinheil can be quite useful for working small format digital into early Pictorialist-like images. 

At this point I'm finding I have many good options from which to choose.  German.  Japanese.  Cooke triplet.  Zeiss tessar.  Steinheil Antiplanet (I have a Staeble 85mm that is of this formula).  All of these are good in one way or another.  I just have to work with them to see where I can go from here. 

Blur Radius vs Blur Falloff ~ Ricoh Riconar 55mm f/2.2

The first first element focusing lens I stumbled on was a Ricoh Riconar 55mm f/2.8 four element 4 group design lens.  It's a strange beasty in terms of lens design, but these seem eminently useful for soft focus work near wide open.    Stopped down the lens is as sharp as anything in the Toy Bin.  Versatility is strong in this one.

Since this is a Pentax K-mount I can't use the first element separation to manage softness level the way I do the m42 thread mount Cosina, Steinheil, and ISCO lenses.  I don't have a helicoid for K-mount.  However, at wide apertures there are plenty of optical imperfections no matter the focus distance.

Here's how to read the following graphs. Please keep in mind that these are for Full Frame digital.  APS-C is slightly different, as we may see in future posts.

 

 

Comments ~

To me it's interesting to see how aperture effects blur.  Bare lens or filtered, aperture can help manage softness levels.

Many of the Ricoh lens/filter combinations are well within old brass-era soft focus lens ranges.  This helps explain why, intuitively, I've felt this was a good Soft Focus lens on Full Frame digital formats.

While there may never be one lens "to rule them all", this little Ricoh seems well up to the task. 

Blur Radius vs Blur Falloff ~ Nikon Nikkor 85mm f/2 Ai

The following is on the heals of looking at another very well corrected, very sharp lens, the ISCO Westromat 50mm f/1.9.  My sweet little Nikon Nikkor 85mm f/2 is a unit focusing ernostar 5 element, 5 group formula lens and is the subject of today's investigation.

Reading the Minolta Portrayer filter instruction manual led me to understand that longer lenses (85mm to 135mm) could respond better to certain kinds of filtration. 

Here's how to read the following graph. 

 

Comments ~

There are several lens/filter combinations that fall into the old brass soft focus lens blur ranges.  This is rather exciting to see and it makes me wonder if soft focus filter designers knew/know more about their craft than I've in the past given them credit for?

One aspect of using a well-corrected lens for soft focus work is that the edges of the field may behave differently than they did in early optics.  

However, as is carefully noted in many journals and writings of the day, including  Biblioteque de la Revue de Photographie -  L. de Pulligny - C. Puyo "Objectifs d'Artiste Practique et Theorie des Objectifs et Teleobjectifs Anachromatique" - Biblioteque national de France (BnF), longer lenses were often the focal lengths of choice to very specifically avoid field edge aberrations at wide apertures (ie: portraiture).

In fact, the only photographer I know of who has succeeded, to my way of thinking, of leveraging field edge problems to outstanding effect is Alex Timmons.  Which means the Nikkor 85mm may be just perfect when used with soft focus filters in the more traditional way.  The time has come for me to validate this in the "real" world.

Blur Radius vs Blur Falloff ~ ISCO Westromat 50mm f/1.9

The ISCO Westromat 50mm f/1.9 is a unit focusing plasmat 6 element, 4 group formula lens. 

I've been looking at adapting certain kinds of somewhat difficult to find lenses to miniature format for soft focus work in using the first and second element separation control of the focusing ring to manage softness level.  However, I also have quite a stack of unit focusing normal 35mm SLR style lenses, and the brilliant little ISCO Westromat is one of them.  

While I am "on a roll" what better time to check two things about unit focusers with regards to potential soft focus work.  First, look at the bare lens wide open (I expect it to be sharp - it takes a lot to design a "bad" lens).  Second, look at what the effect of the filters might be on a very well corrected, sharp, not-at-all-bad lens.

Here's how to read the following graph. 

 

Comments ~

Only the Westromat/Nikon Nikkor Soft 1 combination falls within one of the two old soft focus lens zones.  All other combinations give varying blur radii outside of the old brass lens softness.

Looking at the Blur Falloff tells me that this will give a "fat" blur rendition (40% to 50% luminance measured half way between the leading and trailing edges of blur), even as the Blur Radii measured small compared with first element focusing lenses.  Wherefore I expect this lens used with Soft Focus Filters to deliver a different from Pictorialist softness "look." 

I'll have to spend some time with the ISCO Westromat to see how it behaves in the "real world." It may be just another excellent, sharp, boring 'ol 50mm plasmat that is indistinguishable from fully modern AF.  If that turns out to be the case, there'd be nothing wrong with that, right?

Blur Radius vs Blur Falloff ~ ISCO Iscotar 50mm f/2.8

The ISCO Iscotar 50mm f/2.8 is a Cooke formula, first element focusing, triplet lens.  I'm adapting these kinds of lenses to miniature format for soft focus work by using the first and second element separation control of the focusing ring to manage softness level.  Mated to a helicoid and setting the softness level on the focusing ring, the helicoid is used to effectuate the focus itself.

To show how first and second element separation effects softness level, I graphed Blur Radius against Blur Falloff.  Further, to control highlight "softness", I added a number of different Soft Focus filters to the investigation see to what degree they do their job. 

Here's how to read the following graphs. 

 

Comments ~

These illustrate how the focus ring on the ISCO 50mm can effect the level of softness in an image.  And we can see how Soft Focus filters add softness over the base optics.

Cooke triplets are bog simple, but very well corrected lenses.  I wondered if the German 35mm SLR triplets were derived from the same detailed design specifications, but they are not.  The ISCO is contrasty where the Steinheil is lower contrast but sharper.  

There are other German Cooke triplets, but they are unit focusers and it might be difficult to adapt them to soft focus work.  At this point I'm unable to find any Japanese Cooke triplets.  The closest I can find in first element focusers are tessar formula lenses (such as the Cosina 55mm f/2.8).  If someone knows of a cheap Japanese triplet first element focuser let me know, please.