NEX-7 + Telyt 1:4/280 + up to 3 Extenders

[k-hawinkler]

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I am trying to find out how the APO-TELYT-R 1:4/280 performs on a Sony NEX-7 camera with up to three APO-EXTENDER-R 2x.

 

From left to right: Sony NEX-7 + E-R Adapter + three APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280

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Image shot with: Sony NEX-7 + E-R Adapter +APO-TELYT-R 1:4/280

 

 

Image shot with: Sony NEX-7 + E-R Adapter +one APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280

 

 

Image shot with: Sony NEX-7 + E-R Adapter +two APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280

 

 

Image shot with: Sony NEX-7 + E-R Adapter + three APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280

 

Three of the images were taken with f/5.6, one with f/4.8 as those settings gave the best results. ISO=100.

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[k-hawinkler]

Now let's compare the four shots when mapped to the same feature size.

 

Image shot with: Sony NEX-7 + E-R Adapter +APO-TELYT-R 1:4/280. 100% crop

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Image shot with: Sony NEX-7 + E-R Adapter +one APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280. Size reduced to 50%.

 

 

Image shot with: Sony NEX-7 + E-R Adapter +two APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280. Size reduced to 25%.

 

 

Image shot with: Sony NEX-7 + E-R Adapter + three APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280. Size reduced to 12.5%.

[k-hawinkler]

A little over nine miles - direct line of sight - from my location is a fire lookout tower on top of St Peters Dome, NM.

 

I took this image this evening with this configuration: Sony NEX-7 + E-R Adapter + three APO-EXTENDER-R 2x + APO-TELYT-R 1:4/280

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The next image shows a 100% crop of the building

 

 

One also can hike up to that mountain top and take this picture from the far end of the tower.

 

 

One can clearly identify the antennas to the left in this image with the antennas in the previous image to the right.

[lm_user]

On my screen - it looks like a yellow color shift as you add extenders

[dkCambridgeshire]

When using 3 extenders, the effective aperture when the lens is set at F5.6 is f44 which is unlikely to be the optimum aperture. Might be better to use f4 which gives an effective aperture of f32 ... but even this is likely to show diffraction effects. These extenders were not designed to be used in threes but they do work ... sort of ... if you can live with the resultant long exposures ... and if you can afford to buy three of them!

 

Using the NEX-7 the effective focal length of the 280mm is: 420mm, 840mm (1 extender), 1680mm (2 extenders) and 3360mm (3 extenders) .

 

Let's see some shots of the moon ... that might really show if the combinations are worth using.

 

And I can't help thinking that ISO 100 is not the best rating to use when working at such small effective apertures?

 

Very interesting technical exercise ... but you could probably buy a 560mm Telyt for less than the cost of two Apo extenders and on a cropped sensor get better results ... and then with just one 2x extender have the equivalent of 1680mm.

 

Best wishes

 

dunk

[luigi bertolotti]

My quick impression :

ONE APO2x : sharpness doesn't suffer at all, colortones a bit more "flat"

TWO " : sharpness marginally suffers, color tones as obove

THREE " : sharpness suffers, marginal color fringing effects, but usable

[k-hawinkler]

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On my screen - it looks like a yellow color shift as you add extenders

 

 

Hi there,

 

Thanks for the feedback. Much appreciated. You maybe right or not. I don't know.

 

I wouldn't draw any conclusions of this sort from the presented images in post #1 or #2.

Those images were processed in CS6, making heavy use of clarity, contrast, and curves.

 

I also noticed that on the 8x (three extenders) image I accidentally had an Exposure Bias Value= -0.3.

So, I replaced that image with one of Exposure Bias Value= 0, just like the others, in the following link.

 

As I also have the full size 6000x4000 OOC JPGs, I posted them unmodified here, including Exifs and dust spots:

 

2012-09-15 3•NEX-7+Telyt 280/4 - winklers' Photos

 

Hopefully, those JPGs permit you to form a more accurate impression.

 

My take, looking at those JPGs: The more extenders in use - even the best ones - the more degradation of image quality.

 

However, I find the image quality of all four images good enough to be usable for certain purposes.

 

Thanks again for your feedback.

[k-hawinkler]

Hi dunk,

 

Thanks for the feedback. Always appreciated.

 

I like to explore the limits (and beyond) of technologies in general.

Then, when something breaks - figuratively speaking, I pull back and use a certain technology within the limits I found.

Whether that limit is within or outside the original design parameters from the engineers is none of my concern.

 

Please, also see my detailed responses below.

 

When using 3 extenders, the effective aperture when the lens is set at F5.6 is f44 which is unlikely to be the optimum aperture. Might be better to use f4 which gives an effective aperture of f32 ... but even this is likely to show diffraction effects.

 

I thought it was f/45, but I may be mistaken.

 

Anyway, according to Erwin Puts, http://www.google.com/url?sa=t&rct=j&q=erwin%20puts%2C%20diffraction%20limit&source=web&cd=5&sqi=2&ved=0CEQQFjAE&url=http%3A%2F%2Fen.leica-camera.com%2Fassets%2Ffile%2Fdownload.php%3Ffilename%3Dfile_1864.pdf&ei=iOZUUPXIBJGByAH69YHoBg&usg=AFQjCNGuXa_VDZH2QY3wC90LFSfWZizyUg&sig2=NYgxjWFo6lGiQTGDzqs_Jg, quote:

 

"The 280 mm f/4 Apo-Telyt-R lens is one of the e(sic!)very few lenses

that is truly diffraction-limited. This means that the optical

aberrations are so small that the size and shape of the image

point is governed solely by physical laws."

 

I interpret this to mean that this particular lens is already diffraction limited wide open.

 

As my vision and therefore my focus isn't perfect, I also have to take advantage of increasing Depth of Field effects with smaller apertures.

So I shot all the images from f/4 to f/8 in 1/2 stop increments, and after carefully examining those images, I chose the ones that looked "sharpest" to me.

That's how I ended up with mostly f/5.6 shots.

 

These extenders were not designed to be used in threes but they do work ... sort of ... if you can live with the resultant long exposures

 

So?

 

... and if you can afford to buy three of them!

 

That sounds like sour grapes to me!

 

Using the NEX-7 the effective focal length of the 280mm is: 420mm, 840mm (1 extender), 1680mm (2 extenders) and 3360mm (3 extenders) .

 

Well, you seem to have corrected the originally posted NEX-7 Crop Factor of 1.4x to the Focal length multiplier of 1.5x as quoted by Sony Alpha NEX-7: Digital Photography Review.

 

Excellent! Thanks.

 

I have posted back in February a similar calculation for the Telyt 1:5.6/560 here: Saint Peter Dome Watchtower ...: Leica Talk Forum: Digital Photography Review

Here is an update of that table:

 

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Let's see some shots of the moon ... that might really show if the combinations are worth using.

 

In fact, I did. The problem with this many extenders is that the image of the moon doesn't fit anymore on an APS-C size sensor!

 

And I can't help thinking that ISO 100 is not the best rating to use when working at such small effective apertures?

 

I see your point! Please, see my table above. But I took here pictures of a pretty static object - a telephone pole - and wanted to make only a limited specific point.

 

Very interesting technical exercise

 

Thank you.

 

... but you could probably buy a 560mm Telyt for less than the cost of two Apo extenders and on a cropped sensor get better results ... and then with just one 2x extender have the equivalent of 1680mm.

 

In fact, I already own several 560 mm lenses.

The cost question is really OT in a technical merits discussion.

Of course, when purchasing an item it can be very important.

 

Back to the technical part. Best image quality is not always the most important factor when choosing a camera/lens combination.

Here is an example of two systems that effectively accomplish the same thing. http://www.l-camera-forum.com/leica-forum/2172544-post31.html

 

 

With my eyes, image quality is probably more affected by whether I nail focus or not rather than by the optical qualities of the camera/lens system I use.

I know which of the two systems I would prefer taking on a strenuous hike.

 

It seems to me that the APO-TELYT-R 1:4/280 with extender(s) can be quite an effective tool that doesn't suffer from http://www.l-camera-forum.com/leica-forum/2163503-post139.html, quote:

 

"higher contrast details in the background have bright green and magenta edges"

 

as explained by Jaap here: http://www.l-camera-forum.com/leica-forum/2164333-post144.html, quote:

 

"That is logical. It is an Achromat (corrected for two colors), not an Apochromat (corrected for three)"

 

Best wishes

 

dunk

[k-hawinkler]

My quick impression :

ONE APO2x : sharpness doesn't suffer at all, colortones a bit more "flat"

TWO " : sharpness marginally suffers, color tones as obove

THREE " : sharpness suffers, marginal color fringing effects, but usable

 

 

Hi Luigi,

 

Many thanks for your feedback, as always.

Please, have a look at the full size 6000x4000 OOC JPGs that I posted here:

 

2012-09-15 3•NEX-7+Telyt 280/4 - winklers' Photos

 

I am curious whether those images change your impression?

[Michael Geschlecht]

Hello K-H,

 

Well done.

 

As an empiricist, like you, I wonder what would happen if you changed the order & combinations of the various extenders?

 

There are 16 possible combinations/variations of equipment which, together, would produce your 4 pictures.

 

Furthermore: I wonder what would happen @ different apertures & different distances?

 

btw: What is wrong w/ a piece of the Moon?

 

Best Regards,

 

Michael

[jankap]

Very nice experiments. Your tripod earns a medal too.

And very good results.

A piece of the moon would be interesting, indeed.

Jan

[jankap]

Moonphoto

According to an article somewhere in LuLa the movement of the earth requires the following procurement, if there is no tracking mechanism.

The number 600 divided by the focal length in mm (FF eq.) delivers the maximum exposure time to get a sharp picture.

We have here a focal length of 3360 mm. This gives an max. exposure time of 1/10 sec. Is that possible? Of course, the moon is very bright.

Jan

[jaapv]

 

 

Anyway, according to Erwin Puts, http://www.google.com/url?sa=t&rct=j&q=e

 

I interpret this to mean that this particular lens is already diffraction limited wide open.

 

That is indeed correct. However, that does not mean that it is immune from small-aperture diffraction effects.

For virtual small apertures it does not make a difference of course - just don't stop this combo down (too much)

[k-hawinkler]

Hi Jaap,

 

Agreed. Most often I shoot this lens wide open. It really has amazing performance. Thanks.