Printing-Nikkor 150mm Vignetting on A7r3

[e6filmuser]

The image circle of my version of this lens is ca 30mm. It wil lalmost fill the frame (first image) but the very corners are dark. The edge of the image circle will not be the best quality that the lens will deliver.

To overcome these two issues, I decided to use a x1.4TC in an unconventional way. Normal use is to spread the middle part of the image, from a lens which fills the frame without the TC, over the frame. This time, I am spreading the image to cover the frame when the lens without the TC does not.

This exercise is about filling the frame and not about pixel peeping to see what the lens does. It was hand-held anyway and I was not concerned about exact same focus with and without the TC.

First I set the extension for 1:1 (210mm*). I positioned the movable diaphragm to its position for 1:1 compensation. This was unchanged for the TC because it is what the lens delivers, not how I modify it which matters for that adjustment. The lens was set at f8. Those setting remained fixed.

* The TC adds 20mm.

I then took the two images, the first without and the second with the TC. (The crop factor would affect the effective aperture and DOF, again not of interest).

The extension is of Olympus OM components, two telescopic extension tubes.

(Before anyone gives the old story about a TC degrading the lens, it magnifies flaws. End of discussion).

For my purposes, I have achieved what I set out to do.










With TC:

[kds315*]

Yeah, you have the old version with its rather small image circle - but it has the correction adjustment ring
which allows to fine tune the lens to the magnificaion in use, which the new model does not have!

Great apo lens, you're going to love it!

[e6filmuser]

Klaus,

I've had it for several years but have been waiting for the right camera to show its full potential.

I have used it on m4/3. On the day it arrived I shot this.

[dickb]

I see you are using Olympus telescopic tubes. These have a fairly narrow inner diameter, 36mm to be precise. In some combinations this will introduce extra vignetting on full frame cameras. Perhaps not with your version of the 150 PN, but you may gain a few extra mm by using wider tubes.

[e6filmuser]

[dickb]

[pdccameras]

Great caterpillar shot! If it's a stack, how many exposures did you make?

[e6filmuser]

[e6filmuser]

I have approached this from a different angle.

I set the Printing-Nikkor 105mm (not the 150mm) at 1:1. That is an extension of 165mm. The lens was at f8.

This was somewhat free-lensing as I could not find an adapter. So I chose the best.

As you can see from the first image, there is no more than the merest hint of vignetting. (I was not concerned with accurate focus, just with the corners of the final image).

I then increased the extension to that used for the 150mm at 1:1 i.e. 210mm, giving FOV 22mm wide. I shot a painted wall and tiny dark corners appeared. I took a shot without the lens and got a similar result.

So, the tubes are either adequate or a fraction too narrow at very long extensions, depending on the lens. For the latter, a TC does what is needed.

So, having researched and measured (white disc projected onto paper) the image circle, an established it as 30mm, it seems to cover the 36mm sensor, if perhaps not with the edges of the images being at their best, not often crucial for macro,

[kds315*]

[Lightshow]

+1 looks great for a single shot.

[e6filmuser]

What is happening with the vignetting is a combination of two factors.

The sensor is 36mm wide. A framed transparency shows about 34mm of image width. So, in film days, this vignetting would not be an issue.

As we all know, a straight stretch of railway lines appear to converge into the distance. The longer the extension, the more likely it is that we start to see the inside of the tubes. As the distal tubes are seen first, the remedy would be to put a wider one directly behind the lens, no need to replaced the nearer ones.

The image circle of a 35mm format legacy lens, for producing transparencies with 34mm showing, was, with Olympus OM anyway, of 43mm diameter, only the best, inner parts being viewed. So, optically discarding the outer parts of a 30mm disc by using a TC seems a good tactic. In addition, the minimum aperture of f11 of this lens is what I would use on m4/3 for most subjects and f8, effectively f11 via the TC, might give a better quality overall.

Alternatively, I have no problem with cropping off, say, 5% around the perimeter of the images.

I have options.

The lens has superb performance at up to 2:1, requiring more extension...

[e6filmuser]

A7r with Printing Nikkor 150mm at f11 and flash. I cropped off most of the vignetting. Shot March 2016. I have a x1.5TC on order to deal with the vignetting.

[kds315*]

Yep, sold mine because it is so darn large and HEAVY!!

[simple.joy]

[e6filmuser]

[simple.joy]

[e6filmuser]

[simple.joy]

[e6filmuser]

I admire your manual dexterity!

While I might once have been able to do that, I now have frequent tremors in my left hand from blood sugar issues. I have to take it off the camera to get the shot unless I can rest my elbow on a firm surface. Even flash can't always cope with that. Fortunately, I can usually get the shot, often literally single-handed.

Some of my lenses require over 200mm extension.

[kymarto]

[e6filmuser]

[e6filmuser]

Looking at cropping another way:

If I focus and frame a subject and set the aperture to give the DOF I want and then add a TC, not only do I exclude what, in the image, was around the edges, but I effectively make the aperture smaller and increase the DOF. I can change the DOF by choosing a suitable, wider aperture.

With the saved image, I can do the same cropping but cannot control the DOF and it will automatically increase in proportion to the cropping.

[BrianSVP]

Sorry, but you're 100% wrong.

A teleconverter has zero effect on the depth of field of an image. All it does is magnify the image that's already projected out the back of your lens, effectively "cropping" the image it produces. The depth of the in-focus area does not change at all. So, e.g. if the area that is in focus is 2m on a 150mm lens, putting a 2x teleconverter on it and keeping the aperture setting the same, while you have an equivalent field of view of a 300mm lens, the depth of the area that will be in focus remains 2m.

The reason you lose 4 stops of light on a 2x teleconcerter is because the same amount of photons end up spread out over 4x the area (2 squared), but the iris width and its effects on the in-focus are of the image remain exactly the same.

This magnification effect is also one of the main ways that a TC "degrades" image quality. I put that word in quotes because, while the optics of the teleconverter itself can introduce some aberrations, the main reason a lot of TC images look worse is because it is also magnifying the flaws already present in the lens. So say you have a lens that just barely outresolves the sensor on your camera. Put a 2x TC on, and suddenly you are no longer even coming close to outresolving the sensor. And things like that minor purple fringe you saw before suddenly look a whole lot bigger. This would be true even on a Platonically perfect TC that introduced no aberrations of its own into the optical path.

[e6filmuser]

No, it doesn't change the DOF, any more than it "changes" the FL, but selects the final image with a greater proportion from the centre of the lens, just as closing the diaphragm does. The effect is the same in the final image. "Effectively" is the key.

You are right about degradation.