Thursday, September 13, 2018

Nikon Nikkor 24mm f/2.8 Ai ~ a closer look

I've wanted to like the Nikon 24mm f/2.8 manual focus lens.  Really, I have.  But every time I compare it against the cheap, small, light, modern Sigma 19mm f/2.8 EX DN E, it loses out.  The corners are soft every single time I try to conduct a comparison.  I had a f/2 version of the 24mm Nikkor that behaved just as poorly.

Having owned these lenses for years I sold the f/2 version out of frustration.  The entire experience has been nearly maddening.  I couldn't imagine how Nikon could've screwed up two versions of the same focal length.

Early one morning I was cogitating on the edges of a dream-like state and something occurred to me.  I suddenly felt I should check for field curvature.  Figure 1 illustrates the effect I'm talking about.

What I thought about was how Nikon might have designed these lenses to have a plane of focus that was equidistant from the lens (IOW, a curved field).  So I quickly set up a test.  The scene is simple.  To place the two bottles near the edge of the frame, I scribed an arc from the lens where all three bottles sat on that arc.

Then I compared three lenses.
  • Nikon Nikkor 24mm f/2.8 Ai at f/4
  • Nikon Nikkor 28mm f/3.5 Ai at f/4
  • Sigma 19mm f/2.8 EX DN E at f/2.8
I thought the 24mm Nikkor would show an arc that described the point of focus for that lens.  After having used the 28mm f/3.5 I thought it would show a point of focus as a straight line.  I knew the Sigma would be a flat field lens.  I've used this one for years and it is my reference lens for resolution and field flatness in this focal length range.

Here is the scene setup.  As you can see, the bottles near the edge of the frame are well forward of the railing.  The railing represents the straight line.  The three bottles were placed on an arc equidistant from the lens, where the center bottle is resting against the railing/straight line.

Scene Setup ~ Nikon 24mm f/2.8 Ai

Here are the results (click on the image and select the full resolution image to look at the details).

Field Curvature Comparison
Indeed, the 24mm f/2.8 Ai Nikkor appears to be designed with a point of focus that is equidistant from the lens across the field.  This, to me, means it is deliberately not a "flat field" lens.
With this lens, however, the portion of the image that is in focus does not "pull" or exhibit sagittal distortions.  The subject is rendered "naturally".  And this may be the very reason why the lens was designed this way in the first place.
Considered in this new understanding, the Nikon Nikkor 24mm f/2.8 is actually a very fine optic.  I just have to keep in mind it's characteristics when using it.
As for the 28mm f/3.5 lens, the edge performance at f/4 is not sufficiently good for me to draw any conclusions about it's design nor field curvature.  I could've stopped the lens down further, but the depth of field might have been too great for me to detect it's point of focus at the edges of the frame.
The control lens, however, is quite outstanding and, though the effect is subtle, the railing is more in focus than the bottles.  This re-confirms for me that it's design is more "flat field" than the Nikkor 24mm.  Not "better" than the Nikkor 24mm, just "different" and more in line with what I expected (before conducting this little test).

Illustration ~ Fig 1
Figure 1

Friday, September 07, 2018

Hyperfocal Distances ~ Nikon Nikkor 24mm f/2.8 Ai

Recently a friend explained to me that he was having trouble focusing a Zeiss 25mm manual focus lens on his Nikon DSLRs.  Since very wide angle lenses give deep depths of field I suggested to him that he set the lens at it's hyperfocal distance, stop the lens down to f/11 and "call it good to go."

He wasn't familiar with the term "hyperfocal."  So I whipped out my favorite depth of field calculator and suggested he put the focus at 6 feet 6 inches, set the aperture to f/11 and that everything from 2 feet to infinity would be in focus.  I asked him to let me know what he thought after he tried it out.

Well, needless to say, he was thrilled and he sent me a couple sample images.

Which gave rise to the question of how this might look in practice.  So I took out a Nikon Nikkor 24mm f/2.8 Ai, setup up a tripod, and photographed a scene with different subjects at different distances to show how it works.

Here is the base scene -

Scene Setup Hyper Focal


And here is a look at the results for the lens focused at the hyperfocal distance, where it is focused at infinity, where it is focused on the foreground, and a look at what happens when a smart sharpen is applied to the hyperfocal image.

Comparison ~ Hyper Focal


What I see is that setting a lens to it's hyperfocal distance does indeed work.  Everything from the orange clothespin in the foreground to the windows at infinity are "acceptably" in focus.  It's a matter of how much of an "airy disk" we can accept before saying something is "out of focus."  Frankly, the detail at infinity isn't all that bad.

Of course, if I took the time to focus on infinity, subjects at that distance were slightly more in focus and the foreground dropped resolution.  When I focused on the foreground the clothespins were slightly better focused and the background dropped resolution.  From the above image you can see for yourselves by how much resolution changes in the various scenarios.

Taking the hyperfocal image and applying a light smart sharpen was rather interesting.  Of course sharpening an image does not add resolution.  It adds contrast to the dark/light transition zones of an image.  That is to say, it adds "apparent" resolution because the human eye sees increased contrast as increased resolution (up to a point).

Walking out into the "real world", here are a couple examples how how setting the Nikkor 24mm at f/11 and the focus at the hyperfocal distance looks in practice.


Passages ~ Paris, France
Passages ~ Paris, France

Monday, August 20, 2018

Learning to trust Focus Peaking

One of the many subjects I enjoy photographing are automobiles and motorcycles.

Twice a year here in Paris there is a large gathering of cars and bikes.  In trying to capture the overall atmosphere of the event I like to photograph the vehicles at rest and in motion.

la traversee de Paris estivale 2018


Over the years I've become somewhat dependant on autofocus when working with cars moving on the road.  I thought I'd lost the ability to accurately track a vehicle and come away with a very sharp image.

However, I've noticed that sometimes an AF lens will lock on to something that I don't want.  For instance the AF system can lock onto the foreground or background, particularly if the subject's contrast is lower than the surrounding area.  This has happened to me even when I set an AF point (such as center) to try and limit the AF to "seeing" the subject.

This mis-focus state happens surprisingly often and after some car events I have found many images that were less than sharp where I intended it to be.  It didn't matter if I used a DSLR or a mirrorless camera.

la traversee de Paris estivale 2018


Which got me to thinking about trying old manual focus lenses and learning to work with my Sony mirrorless cameras "focus peaking" function.  It would take practice and these car events happen only twice a year.  Practicing on cars driving on the street outside of these events is problematic as people here don't like their picture taken and will call the police.  I'd have to just jump in and see what I could do during la traversee de Paris itself.

Fortunately I had a glimpse of what might be possible when I photographed vintage automobiles in front of les Invalides.  As some of the cars were in motion I snapped a few images while trying to keep the "focus peaking" properly over the subject.  It was a little complicated because those old 35mm film days muscle memories of focusing on race cars had atrophied.  But I came away with enough very sharp images that I was rather happy.

la traversee de Paris estivale 2018


A month later I found myself snapping photos of quickly moving cars on la place de la Concorde.  My setup was a Sony A6000 camera, a Lens Turbo II focal reducer, and a lovely Nikon Nikkor 85mm f/1.8 K pre-Ai lens.  The focal length of the lens seemed to be about "right" for reaching out and capturing images of event participants.  Interesting cars were coming from all directions and I worked the manual focus ring like a madman trying get the right "focus peaking".

Once I got home and was able to review the outcome I realized I lost perhaps 5 of the hundreds I took due to the lack of critical sharpness!  And two slightly out of focus images I was really interested in keeping were easily sharpened up using a "smart sharpen" function during image processing.  That "hit rate" far exceeds anything I've ever experienced with AF lenses.  It didn't matter if I shot the 85mm at f/5.6 (where there is a bit of depth of field) or wide open (where I really need to "nail" the focus to keep things sharp).

la traversee de Paris estivale 2018


I'm pleasantly surprised and the outcome pleases me.  I can feel those old muscle memories about how to work manual focus lenses in quickly changing situations coming back.  It's a good feeling.

But it brings a question: Why am I _still_ wrangling over what to take to Nice during the winter?  You see, there will be a Carnival there and it will be yet another quickly changing environment.  For whatever reason I'm still a bit worried about taking my old Nikkors in place of the AF optics.  What to do?  Fortunately I have a few months to sort it all out.

la traversee de Paris estivale 2018

Friday, August 10, 2018

Historic Racecars in Black and White

In a previous post I illustrated the use of old Nikon Nikkor manual focus lenses to photograph a classic automobile show.  These older lenses tend to "round" off the top end of the curve, making highlights easier to control in processing.  It is a simple process to keep the highlights creamy and luscious.

le Mans Classic ~ 2018


Modern lenses tend to be a bit more "contrasty" in the highlights.  As such when using modern autofocus optics I've found I need to gently modify the highlight areas by using a "rounded" curve toward the top end.

After the teuf-teuf show I visited le Mans for the 24 heures Classic event.  This was the second time that I've been (the first visit being in 2016).  Not wanting to miss a shot by rushing to manually focus (I wasn't yet fully comfortable in trusting my manual focus abilities) I took three cameras mounted with three different autofocus lenses.

The first camera was a Sony NEX-5T with a Sigma 30mm f/2.8 EX DN.  The second was a Sony A5000 with a Sigma 19mm f/2.8 EX DN.  It was this camera that I put on the end of a monopod and remote triggered using a cell phone.  This was a wonderful solution for getting into those "hard to reach" places.  The third camera was a Sony A6000 and a Sony 55-210mm f/4.5-6.3 SEL OSS.  This is the setup I would use to "reach" out and "compress" the distance between me and a subject.

le Mans Classic ~ 2018


Le Mans has been hot and dry in the two years I've been there.  A hat (the one I used to wear to combat the sun in India), a sack lunch, and bottled water are basic requirements.  I selected Friday as the best day to be there.  The crowds on Saturday and Sunday can be massive.  To avoid as many people as I could I took a 07h30 TGV out of Montparnasse.  Le Mans is only an hour away and I was able to get to one of the entry gates just as they opened at 09h00.

Hot footing it over to the paddock meant I had to avoid strong temptation to take photographs of private cars as they arrived.  There are areas set up all around the infield for car clubs.  These clubs come from all over Europe and some very interesting automobiles are on display.  They would have to wait until I was done working the paddock and racetrack.

le Mans Classic ~ 2018


I can get pretty excited seeing old racecars.  Ferraris, Jaguars, Alfa Romeos, early Bentleys and the oh-so-French Bugattis.  These and many many more marques and makes of racecar are on display as they prepare for a weekend of racing.  The atmosphere is even better than anything I read as a young boy in Road and Track magazine.

There is simply too much happening all at the same time to take it all in.  I did my best to concentrate on cars I was most interested in.  From time to time I would stop and talk to car owners and drivers to learn more about them and their vehicles.  The histories are so deep and rich.

It's difficult to do the subject justice in just one seven hour day, but I did the best I could.  Of course I am looking forward to the next 24 heures Classic in two years.

le Mans Classic ~ 2018

[Note: Here is an album of images from the 2018 Le Mans Classic - including both black and white as well as color works]

Sunday, August 05, 2018

Vintage Automobiles in Black and White

The French are seemingly just as Car Crazy as the English and Americans.  We have so many motor related events that it's hard to keep up with them all and impossible to visit each and every event.  I try to select the events I'm most interested in.

Paris-Rambouillet ~ 2018

This year a couple local clubs hosted a Paris to Rambouillet event.  It was for very early automobiles and they would set out from les Invalides.  The cars massed on a Saturday afternoon and set out around sunrise Sunday morning.

I was curious to see what might show up.  There are so many early marques that I know nothing about, and I thought it would be fun to explore and discover a bit.  Of course I wanted to make a few images.

For obvious reasons the image style that appealed to me most was black and white.  To answer questions about image quality and focus-peaking focus accuracy I wanted to take two lenses.  The first was a Nikon Nikkor 24mm f/2.8 Ai that tested a little poorly way out in the corners.  The second lens was a Nikon Nikkor 85mm f/1.8 K that tested ever so slightly "soft" wide open.

Paris-Rambouillet ~ 2018

My wife and I headed over the see the cars as they arrived and the public display the clubs put on in front of les Invalides.

As you no doubt know, I really enjoy using Sony APS-C mirrorless cameras.  But one of the things I've been too "chicken" to test in a "live photoshoot" was focus peaking accuracy on moving subjects.  With plenty of time I can magnify the scene and carefully focus on the part of the subject I want in maximum focus.  But with moving objects I wondered how far my "hit rate" might fall when using non-AF lenses.

Taking a deep breath and risking being disappointed by the lack of sharp images I dove in to see how things might come out.

Paris-Rambouillet ~ 2018

Looking at the images from the Nikon Nikkor 24mm f/2.8 Ai the first thing I considered wasn't the edge performance.  It was the composition and lighting of the subject.  Only when I forced myself to look across the image did I think about the edges.  They seem just fine.

To test the focus-peaking accuracy in situations with no time to magnify a section of the scene I shot the Nikon Nikkor 85mm f/1.8 K wide open.  Over the past few months in working with test subjects I observed where the sharpest images are achieved relative to the focus-peaking line widths.  So I had a little confidence that things might come out OK, but until everything was in motion and in play I couldn't be certain I had the best/correct technique.

It turns out that using a Sony A6000 with focus-peaking through the EVF I was able to get a very high focusing accuracy "hit rate."  Frankly, I was more than a little surprised.  And the images were sharp, too, even wide open.  This was important to me because AF lenses on the same camera would sometimes choose an AF point behind the intended subject.  Now, it appears, I can control the focus point with surprising accuracy and better consistency.

Paris-Rambouillet ~ 2018

While I might not declare a Year of Manual Focus Lenses Only (there are still situations where I feel I have to trust AF), unofficially more and more of my work is and will be made using old Nikon lenses.

Saturday, June 30, 2018

Comparison ~ Nikon Micro-Nikkor 55mm f/3.5 pre-Ai and f/2.8 Ai

The insanity continues.

A friend recently sent me his old Nikon Micro-Nikkor 55mm f/2.8 Ai.  I already had a copy of the earlier lens, a 55mm f/3.5 pre-Ai.

Playing around, I took a look at how well these worked with a 52mm threaded reverse adapter that flips the lens around on a camera.  I learned that the adapter worked best when the subject to lens distance was shorter than the focal length (otherwise the edges went soft very quickly).  But for everything else macro a normally oriented lens worked best.

In general use, I couldn't help but notice the f/3.5 "felt" sharper wide open than the f/2.8 at f/2.8.  But stopped down, everything was brilliantly sharp out of both lenses.

Macro is not what I do, but, still playing around and wondering about "things" I thought it might be fun to see how the two Micro-Nikkor lenses behaved at 1:2 magnification (as marked on each lens).

Setup -
  • Sony NEX-5T, 100ISO, AWR converted in Sony's software 
  • Big Beefy Manfrotto tripod 
  • Nikon Micro-Nikkor 55mm f/2.8 Ai
  • Nikon Micro-Nikkor 55mm f/3.5 pre-Ai 

Comparison Results -

[If you click on the image it'll take you to the Flickr hosting site. Once there, look at the file at full resolution. In many cases the differences between lenses is small and likely can't be seen until you take a squint at the comparison at 100 percent.]

Nikon 55mm f/2.8 and f/3.5 Micro-Nikkor Comparisonf28f35


Comments -

Indeed, the Micro-Nikkor 55mm f/2.8 shot at f/2.8 is softer than it's brother lens shot at f/3.5.  The difference isn't that great, but it is noticeable (otherwise why comment on it, right?). 

However, the f/2.8 lens at f/4 is sharper than the f/3.5 at f/3.5.

From f/5.6 on down both lenses look nearly identical.

One of the things I like about shooting with a Micro-Nikkor is that the image field is flat and without distortion.  Images can be sharp all the way to the edge and I don't have to apply pincushion/barrel distortion corrections.  As a bonus, the out of focus rendition of both lenses shot wide open is very smooth and creamy.  I like this since many 50-58mm lenses suffer from over corrected out of focus regions which leads to "soap bubble bokeh".

I suppose I should, for completeness, take a look at how both lenses compare at more normal photography working distances.

Friday, June 29, 2018

Fungus ~ Nikon Nikkor 300mm f/4.5 pre-Ai before/after CLA

It so happened that I picked up a cheap 300mm Nikon Nikkor f/4.5.  After receiving the package I realized why it was so cheap.  Here was a second opportunity to see how fungus could affect image rendition.  This time the lens was pretty clouded with champignons.  The inside forward elements were covered with nastiness.  And it looked like the inside and outside of the rear element set hadn't ever been cleaned.

Setup -
  • Sony A6000, 100ISO, AWR converted in Sony's software 
  • Big Beefy Manfrotto tripod 
  • Nikon Nikkor 300mm f/4.5 pre-Ai with very very light scratches on the front element (as the control optic)
  • Nikon Nikkor 300mm f/4.5 pre-Ai filled with fungus (before CLA) and cleaned (somewhat)
  • Lens Turbo II adapter

Comparison Results -
[If you click on the image it'll take you to the Flickr hosting site. Once there, look at the file at full resolution. In many cases the differences between lenses is small and likely can't be seen until you take a squint at the comparison at 100 percent.]

Nikon Nikkor 300mm f/4.5 pre-Ai


Comments -

The control optic is a fine lens.  Sharp from wide open, this lens, even with the light scratches, is contrasty and just plain downright good.

The fungus infected 300mm did indeed show performance degradation.  This really is no surprise.  There was so much gunk and crud that just about any amount of cleaning would've done the lens good.  And it did.

However, the CLA'd lens still suffers for a very slight lack of contrast.  A re-inspection of the lens revealed that the inside of the rear element set is a little cloudy.  The way Nikon manufactured these lenses makes it difficult to disassemble.  The various threaded retainers tend to be nearly impossible to remove.  So... I'm not sure what to do with the lens... perhaps I'll sell it as is?