My thoughts on the Kipon Medium Format "Speedbooster"

[Nikkor]

This is totally pointless, there is no difference between formats

[tupp]

6 hours ago, Don Kotlos said:

Many people have done the equivalence tests including many people on this forum (here, here, here, here & here). 

Again, nobody has yet done a conclusive, worthwhile "equivalence" test.

 

I don't mean to sound harsh (nor to hijack this thread), but the pages you linked either lack actual equivalence tests or give dubious, useless results.

 

The first page linked doesn't seem to contain any equivalence test -- it is just an essay titled "Sensor Crop Factors and Equivalence."  If there is an actual test of DOF equivalence on that page, please point it out.

 

The second page you linked actually contains a DOF equivalence test that seems to demonstrate that optics for larger sensors yield  quite a significant difference in DOF when compared to the DOF of to smaller optic.  So, it seems to demonstrate that the equivalence principle fails.  I spotted the differences immediately, and I will point to some of the more obvious discrepancies.  Here are the two images flashed back-to-back in a gif file:

The bottle in the foreground stays sharp in both images, but look at how the sharpness of the bush and car dramatically change (red circle).  Look at how the sharpness of the cast shadow and grass change (yellow circle).  Look at how the sharpness of the building changes (blue circle).

 

Does the DOF in these two flashing images seem equivalent?  It doesn't seem the same to me.

 

Now, I am not very good at making gif images, and I apologize for the rough dithering, but you can further confirm these differences yourself by downloading the two images from the linked site and switching back and forth between them in your favorite image viewer.  Actually, anyone should be able to see the difference inside the red circle, merely by viewing the two images on their web site.

 

On the other hand, I have to confess that this test is worthless.  In the first place, it appears that the tester failed to eliminate the variable of in-camera sharpening, so it is very possible that one camera sharpened its entire image while the other camera didn't.  More importantly, the tester put a lot of air between the foreground and the distant background.  Some of the "magic" of larger format optics happens in that air between the FG and BG, but this comparison has no objects nor charts in that air to reveal what is happening to the focus there.  This fatal blunder occurs in almost every equivalence test that I see.

 

The third link that you gave is the Brightland Studios test which has been referenced by me and others on this forum in several threads.  I am afraid that this is yet another misguided experiment in which the equivalence principle doesn't seem to hold up.

 

The tester made two comparisons using the same camera and zoom lens in both tests.  First he compared the equivalence between camera's full sensor read-out and the camera's crop mode:

With the front of the subject sharp in both images, the apparent counter top (red circle) in the distant background,changes focus, and does not appear to be equivalent in the two images.  Likewise, there is another detail in the distant background (blue circle) lacking equivalence of focus between the two test images.  There seems to be other subtle focus discrepancies, that I will mention later.

 

The tester acknowledged that the camera might apply a different degree of image processing/sharpening in full sensor mode than it would in crop mode, which could make the focus/DOF of the two test images seem more similar.  So, he made another comparison, in which he shot both images in full sensor mode, but one of the images was shot optically as if it was in crop mode.  That "simulated crop mode" photo was then cropped to matching size in post. Thus, in this second comparison, there was optical equivalence along with no difference in image processing/sharpening between the two shots:

As you can see, with the difference in in-camera processing eliminated, there are significant areas of non-equivalence. In addition to the counter top changing, the bokeh changes size and softness (red circle), while the front of the subject remains sharp.  The Canon logos conspicuously change their focus (blue circles) which happened more subtly in the first comparison, while the top buttons on the camera (yellow circle) do likewise.  Part of the tripod head (green circle) also conspicuously goes in and out of focus, and it does so more subtly in the first comparison.

 

So, the equivalence principle certainly seems to fail here, as well.

 

However, there are serious problems with this test.  For one thing he used the same zoom lens on all images.  Not only does the character of the lens look the same in each photo, but aperture position (virtual/actual) doesn't necessarily change with the zoom's set focal length.  So the zoom lens' aperture position probably doesn't match the differing aperture positions found on a prime lenses of the same focal length.  This discrepancy could make the DOF appear more uniform than if the test were done with separate prime lenses of different focal lengths.

 

Also, these Brightland Studios tests suffer from the same lack of any objects/charts in the important long stretch between the foreground subject and the distant background, so there is literally "nothing to see here."

 

The fourth and fifth links you provided seem to go to different pages of the same earlier thread concerning the Kipon MF focal reducer.  I am not sure what you expect me to find on these forum pages, but I do not see any equivalency tests.  By the way, on page two of that very thread, I address the Brightland Studios test in several posts.

 

I am hoping that one day someone will do a proper equivalency test with charts/objects placed at regular intervals extended behind the foreground.  Ideally, one camera would use a tiny format (2/3" or S16) while the other camera would be a large format (Gonzalo Ezcurra's Mini Cyclops, the LargeSense back, or a shift/stitch adapter).  Of course, a full frame camera with this Kipon focal reducer would be interesting to compare, too.

 

[zerocool22]

Any video's yet?

[Andrew Reid]

I am mega looking forward to how this turns out.

Also there are some fast optics for medium format at F2, bucking the usual trend for F2.8 and F4, which should look amazing on full frame.

But it isn't all about shallow DOF - lots of other benefits with the way the focus rolls off and how much depth you get to play with in your composition, the three dimensionality of it.

The image circle you get from this adapter is enormous... larger than the Sony 50MP sensor in the Fuji GFX, Hasselblad X1D and Pentax 645Z.

My take - http://www.eoshd.com/2017/02/sony-a7r-ii-a7s-ii-go-medium-format/

[webrunner5]

The biggest advantage of moving to a larger format, even if it is film based or digital based, is Lens Diffraction, ergo the lack of it. The bigger you go film, sensor area wise the bigger you can go F stop wise or actually closed down. I know it is always ass backward.

That is why there was a F64 club back in the Ansel Adams, Weston days using 8 x 10 cameras. You can get tons of stuff in focus without distortion. Maybe not totally stopped down but damn close. That is the big problem with m4/3 it creeps in a f8 a lot and damn sure is at F11. So this Speed Booster could be damn interesting for that reason alone.

[tupp]

On 2/21/2017 at 0:47 AM, zerocool22 said:

What is the widest lens you can use with this adapter? (I like the 35mm-50mm on full frame)

Don't know what is the widest MF lens that can fit on these adapters, but focal lengths as wide as 35mm were fairly common on MF, which is similar to having a 22mm lens on FF.

 

 

2 hours ago, webrunner5 said:

The biggest advantage of moving to a larger format, even if it is film based or digital based, is Lens Diffraction, ergo the lack of it.

This is a excellent point, and diffraction can affect the focus, and, hence, the DOF roll-off.

 

 

2 hours ago, webrunner5 said:

That is the big problem with m4/3 it creeps in a f8 a lot and damn sure is at F11.

Of course, the greater prevalence of diffraction with small formats is due to the physically smaller apertures of shorter focal length lenses -- not caused by the small sensor/film formats themselves.

[jonpais]

1 hour ago, tupp said:

Of course, the greater prevalence of diffraction with small formats is due to the physically smaller apertures of shorter focal length lenses -- not caused by the small sensor/film formats themselves.

Does this mean that when shooting with a full frame lens like the Sigma 50mm f/1.4 with a MB SB on the G85, diffraction will no longer begin at f/8? 

[webrunner5]

I kind of thought it had to do something with the angle of light rays that enters the lens, to the sensor it has to travel, shorter distance the problem with smaller sensors?? Smaller lens opening.

[Mattias Burling]

As always this type of subject becomes a hot potato.
Some say there is a difference between 4x5 Large Format and a 1" RX100. Others don't agree.
Personally I don't care all that much.

Its also impossible to reach a wide consensus when people saying "this lens is better than that lens" aren't even agreeing on what characteristics is most important in an image. Its all about taste.
The most common misunderstanding is when someone believes all of us rank sharpness number one in a lens feature (I sure don't).

Im going to concentrate on just showing what the thing can do and let people make up their own minds.
Comparing shots will be made, video as well.
Only problem is I haven't had the time and when I did there was a Blizzard.

So all I can say now is, stay tuned.

One thing Ive noticed but need to test more is the lack of chromatic aberration compared to my modern E-Mount Zeiss FE 35mm f2.8.
I will do a side by side of that as well since the pictures Ive compared so far was in a bit different lighting situations.

But regarding lenses

Old medium format lenses are pretty affordable and if you like me still shoot film they where already sitting on your camera.
But, I decided to buy a few more just because of "why not, I like old glass".

Thats when I noticed that there are cheap adapters for Hasselblad, Bronica and Pentacon 6/ Kiev 88 to the 645 formats...
And an old Zeiss Jena with Zebra Stripes for Pentagon 6 aren't very expensive at all...

I bought the 80mm f2.8 and Im looking at their tele prime as well.
As usual Im going to have to be patient with the adapter since its coming from China.

I used to have the Zeiss Zebra 35mm for my NX1 and Digital Bolex as well as a set of Jena C-mounts.
All very tasty

But to at least include some sort of image in the post I will include two photos from last time, both with the 80mm Macro.

This first one is ISO6400 and 1/40 so there is motion blur, not lacking sharpness.

Notice how only the very top-right of the left leaf is in focus. But there you can even make out the tiny tiny hairs.
Like I said last time, "sharp enough"

 

[tupp]

1 hour ago, jonpais said:

Does this mean that when shooting with a full frame lens like the Sigma 50mm f/1.4 with a MB SB on the G85, diffraction will no longer begin at f/8? 

It is my understanding that diffraction from the aperture is a matter of degree, and that the relative amount of diffraction is a direct function of the physical diameter of the aperture.  Diffraction always exists, but the ratio of diffracted light to usable light increases as the aperture closes. 

 

Given two simple lenses of the same focal length, a particular f-stop on one lens should give the same amount of diffraction as the same f-stop on the other lens.  The reason for this is that f-stops are simply a ratio of the focal length over the aperture diameter.  So, two 50mm lenses should have identical aperture diameters at any given f-stop -- same aperture diameter, same diffraction.

 

Of course, there are other variables that affect focus, DOF, and focal plane flatness.

[Mattias Burling]

Here is a random frame thats "only" ISO1000 and 1/60.
Not cropped for some peeping.
I added a vignette in post. Focus sits on the eye but maybe more critical a few cm behind on the head.
Click to enlarge.

[Andrew Reid]

Nice rendering and it has the gentle focus roll off to the background that is very medium format-like, whereas at a fast aperture on full frame that background would be completely creamed out with no detail.

[BrorSvensson]

would love to see the mamiya 80mm f/1.9 on it

[Zachguti]

Registered to keep up on this thread, and because I found this:

I feel like the MF look shines at 10+ feet from the camera. I just can't image as nice an image on FF with an ultra fast 50mm.

[webrunner5]

47 minutes ago, Zachguti said:

Registered to keep up on this thread, and because I found this:

I feel like the MF look shines at 10+ feet from the camera. I just can't image as nice an image on FF with an ultra fast 50mm.

Well you started out very well LoL. Welcome aboard. Nice footage to express your point. Info = Pentacon Six Kipon, A7S, external recorder.

Another reason for me to buy a A7s, damn it! No end.

[jcs]

On 2/21/2017 at 1:29 AM, tupp said:

The third link that you gave is the Brightland Studios test which has been referenced by me and others on this forum in several threads.  I am afraid that this is yet another misguided experiment in which the equivalence principle doesn't seem to hold up.

The tester made two comparisons using the same camera and zoom lens in both tests.  First he compared the equivalence between camera's full sensor read-out and the camera's crop mode:

With the front of the subject sharp in both images, the apparent counter top (red circle) in the distant background,changes focus, and does not appear to be equivalent in the two images.  Likewise, there is another detail in the distant background (blue circle) lacking equivalence of focus between the two test images.  There seems to be other subtle focus discrepancies, that I will mention later.

 

The tester acknowledged that the camera might apply a different degree of image processing/sharpening in full sensor mode than it would in crop mode, which could make the focus/DOF of the two test images seem more similar.  So, he made another comparison, in which he shot both images in full sensor mode, but one of the images was shot optically as if it was in crop mode.  That "simulated crop mode" photo was then cropped to matching size in post. Thus, in this second comparison, there was optical equivalence along with no difference in image processing/sharpening between the two shots:

As you can see, with the difference in in-camera processing eliminated, there are significant areas of non-equivalence. In addition to the counter top changing, the bokeh changes size and softness (red circle), while the front of the subject remains sharp.  The Canon logos conspicuously change their focus (blue circles) which happened more subtly in the first comparison, while the top buttons on the camera (yellow circle) do likewise.  Part of the tripod head (green circle) also conspicuously goes in and out of focus, and it does so more subtly in the first comparison.

 

So, the equivalence principle certainly seems to fail here, as well.

 

However, there are serious problems with this test.  For one thing he used the same zoom lens on all images.  Not only does the character of the lens look the same in each photo, but aperture position (virtual/actual) doesn't necessarily change with the zoom's set focal length.  So the zoom lens' aperture position probably doesn't match the differing aperture positions found on a prime lenses of the same focal length.  This discrepancy could make the DOF appear more uniform than if the test were done with separate prime lenses of different focal lengths.

 

Also, these Brightland Studios tests suffer from the same lack of any objects/charts in the important long stretch between the foreground subject and the distant background, so there is literally "nothing to see here."

 

The fourth and fifth links you provided seem to go to different pages of the same earlier thread concerning the Kipon MF focal reducer.  I am not sure what you expect me to find on these forum pages, but I do not see any equivalency tests.  By the way, on page two of that very thread, I address the Brightland Studios test in several posts.

I did those tests- it's not really possible to do perfect equivalence with physical lenses unless all the settings can be exactly matched. In the first example, the only major difference was shadow detail which could be related to ISO... In the second example, maybe I made a mistake or it's still related to optics not really being equivalent. The 'normal' test matches almost perfectly.

Brain Caldwell, the optical engineer and inventor of the Speed Booster says the same thing regarding FF vs. MF. That's why he wasn't interested in making a MF to FF SpeedBooster...

In any case, the differences are minor and most people couldn't tell the difference. Someone posted computer graphics (ray traced?) examples that matched perfectly, as the math predicted.

[mat33]

Medium format does seem to have better separation of different aspects of the image at smaller apertures, but is this preserved with an optical speedbooster or does the extra glass result in the distortion/perspective/focus transition being the same as an equivalent full frame lens?

[jcs]

3 hours ago, Andrew Reid said:

Nice rendering and it has the gentle focus roll off to the background that is very medium format-like, whereas at a fast aperture on full frame that background would be completely creamed out with no detail.

What proof do you have for this?

[webrunner5]

11 minutes ago, mat33 said:

Medium format does seem to have better separation of different aspects of the image at smaller apertures, but is this preserved with an optical speedbooster or does the extra glass result in the distortion/perspective/focus transition being the same as an equivalent full frame lens?

Yeah good question. I have owned a ton of MF rigs, and other than "Resolution" ergo print size output, I never seen a big difference in the quality, by that I mean look, build, feel of the lens  and look on the final print compared to say Nikkors back them. Some of the Zeiss stuff was of better quality, but...then there was Leica back then FF. And heck Zeiss makes all formats of lenses, from 8mm  to god only knows size.

[Mattias Burling]

9 hours ago, BrorSvensson said:

would love to see the mamiya 80mm f/1.9 on it

I will be able to help you with that