How and Why does 50 APO perform better than other 50s

[hdmesa]

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10 minutes ago, lct said:

You did not focus the better way or your lens has a problem sorry . Did you recompose after focusing if i may ask?

No, I mentioned that in the post – camera position did not move, I just focused on a different spot using the rear LCD.

[lct]

4 minutes ago, hdmesa said:

No, I mentioned that in the post – camera position did not move, I just focused on a different spot using the rear LCD.

You should not get faulty results like that, sorry again. If i may, just use your EVF w/o focus magnification if it bothers you and you'll get way better results. 

[hdmesa]

8 minutes ago, lct said:

You should not get faulty results like that, sorry again. If i may, just use your EVF w/o focus magnification if it bothers you and you'll get way better results. 

I find magnified focusing on the rear LCD is easy to use, and I could clearly tell when something was in focus or not. The center of the frame snapped into focus perfectly. When focusing anywhere in the outer portion of the frame with the 50 Lux (wide open at MFD), the point of focus never becomes sharp, so I took the photo that represented the best possible focus. It could be the field curvature on the 50 Lux at MFD is so strong that the sides of the frame cannot be in focus, and I would have to step back a few feet (which is what I found – stepping back from MFD allowed the sides to be sharper).

Have you used the Lux on the M10-R and reviewed off-center sharpness at 100% magnification? It may be much less forgiving than a 24mp camera.

Edited March 27, 2021 by hdmesa

[lct]

Seems like we cannot understand each other i fear. The center of the frame can in no way be in focus together with the corner in your pic. At f/1.4 and 0.7m DoF is too short for that. If you focus at the corner, the latter will be sharp and the center will be blurred but both cannot be sharp altogether. 

[dkmoore]

29 minutes ago, lct said:

Seems like we cannot understand each other i fear. The center of the frame can in no way be in focus together with the corner in your pic. At f/1.4 and 0.7m DoF is too short for that. If you focus at the corner, the latter will be sharp and the center will be blurred but both cannot be sharp altogether. 

Fact. I think it’s a faulty understanding of DOF and focus plane for hdmesa

Edited March 27, 2021 by dkmoore

[hdmesa]

1 hour ago, lct said:

Seems like we cannot understand each other i fear. The center of the frame can in no way be in focus together with the corner in your pic. At f/1.4 and 0.7m DoF is too short for that. If you focus at the corner, the latter will be sharp and the center will be blurred but both cannot be sharp altogether. 

 

1 hour ago, dkmoore said:

Fact. I think it’s a faulty understanding of DOF and focus plane for hdmesa

 

The crops are from TWO DIFFERENT PHOTOS, each focused on a different part of the frame while the camera position did not move. This is not about DOF, it's about sharpness at the exact point of focus.

For reference in my first post with the samples:

Image 1: Overview to show the subject and camera position
Image 2: Crop from Image 1 (focused on the dangly thing in the center)
Image 3: Crop from the left side of a DIFFERENT photo (focused on a dangly thing on the left side of the frame)

Edited March 28, 2021 by hdmesa

[cboy]

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5 hours ago, padam said:

Here is a comparison with MTF charts included.

https://zhuanlan.zhihu.com/p/352121396

At far distances, the 50mm APO-Lanthar VM is actually sharper at the edges at f/2 compared to the 50mm APO-Summicron-M, although the Leica lens has has higher contrast.

Awesome comparison. I suspect more glass to air surfaces in the vm apo is a factor to lesser contrast compared to the leica apo. But the more correcting elements along with the AA is better for corner sharpness than a floating element from the leica apo?

[lct]

2 hours ago, hdmesa said:

[...] it's about sharpness at the exact point of focus.

Look at my pic above, the one with the book of Cartier-Bresson. I focused on "Bresson" and it is sharp there. You can do the same with your lens if it works normally.

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[MarkP]

On 2/8/2021 at 7:35 AM, 105012 said:

Superachromat adds near-infrared (say, 700–850nm) to the range of wavelengths to be correctly focused. A SuperAPO-Summicron 50mm would probably define an all new price category for Leica!

Easily another $5K for the prefix SUPER- 🙄

[henning]

A couple of things: A superachromat focusses 4 wavelengths on one plane, at one distance. Which wavelengths, and at what distance isn't specified.

What happens to the plane of focus between these wavelengths isn't specified nor what happens at other focussed distances; those other colours may focus very close to the common focus plane, be way off or vary to any degree.

There is no such thing as 'apochromatic glass'. Apochromaticism is a feature of a system, ie, a total optical assembly. Anomalous dispersion glass makes it easier to design high performance lenses with a useful general purpose performance, but anomalous dispersion glass is not necessary. Again, as with superachromats, apochromats focus different colours on one plane at one distance but only with 3 wavelengths, not 4. What happens at other wavelengths and other distances is also not specified. However, with today's lenses and today's marketing, instead of the classical definition, APO means a very highly corrected lens where the plane of focus for all colours is very close to the apochromatic plane and the lens is or nearly is apochromatic over most of the focussing range.

Apochromatic lenses started out as lenses fulfilling a very specific technical requirement, such as process lenses for colour separations. In that application, the three wavelengths of interest were those of the colour filters necessary for the separation, and the focus only needed to be held over a fairly short reproduction range. For a greater or lesser reproduction range a different lens (also APO) was chosen. The lenses were generally of a narrower angle of view, and of fairly modest aperture.

[hdmesa]

12 hours ago, lct said:

Look at my pic above, the one with the book of Cartier-Bresson. I focused on "Bresson" and it is sharp there. You can do the same with your lens if it works normally.

I can’t tell if your focus point is sharp due to the low resolution of the image, and you didn’t post a 1:1 crop. But anyway, I’ve returned the lens because whether defective or not, I need to be able to focus on a similar area at MFD and still get a sharp result, which my copy could not deliver.

[lct]

2 hours ago, hdmesa said:

I can’t tell if your focus point is sharp due to the low resolution of the image, and you didn’t post a 1:1 crop. But anyway, I’ve returned the lens because whether defective or not, I need to be able to focus on a similar area at MFD and still get a sharp result, which my copy could not deliver.

Your lens has little to do with this issue i suspect. If you had an EVF with moving focus point it would be easier to explain i guess but with an M camera w/o EVF i don't find the right words to help you sorry . 

[hdmesa]

16 minutes ago, lct said:

Your lens has little to do with this issue i suspect. If you had an EVF with moving focus point it would be easier to explain i guess but with an M camera w/o EVF i don't find the right words to help you sorry . 

On the M10/P/R, you can move the focus point on the LCD using Live View. Using the EVF would be just another way to do the same thing. Maybe this is not an option on your older M?

 

(Ignore the EXIF shown – both images were shot at f/1.4)

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Using Live View on the rear LCD, I touch the rear screen to move the focus point as shown. Then when I focus the lens, it automatically zooms to that spot:

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Edited March 28, 2021 by hdmesa

[lct]

12 minutes ago, hdmesa said:

On the M10/P/R, you can move the focus point on the LCD using Live View. Using the EVF would be just another way to do the same thing. Maybe this is not an option on your older M?

 

(Ignore the EXIF shown – both images were shot at f/1.4)

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Using Live View on the rear LCD, I touch the rear screen to move the focus point as shown. Then when I focus the lens, it automatically zooms to that spot:

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I have this feature on most of my cams but i thought you have not sorry. Easy to do image magnification on the moved focus point then. You can nail focus on this very point this way and your pic will be normally sharp there unless your lens has a problem.

Edited March 28, 2021 by lct

[hdmesa]

2 minutes ago, lct said:

I have this feature on most of my cams but i thought you have not sorry. Easy to do image magnification on the moved focus point then. You can nail focus on this very point this way and your pic will be normally sharp there unless your lens has a problem.

Yes, I may have had a less than perfect copy of the lens if I am supposed to get sharp results when focusing toward the edge of the frame at the minimum focusing distance of 0.7m. As I mentioned, if I backed up to about 1m, it performed much better on the sides. I may try another copy of the lens.

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[lct]

10 minutes ago, hdmesa said:

Yes, I may have had a less than perfect copy of the lens if I am supposed to get sharp results when focusing toward the edge of the frame at the minimum focusing distance of 0.7m. As I mentioned, if I backed up to about 1m, it performed much better on the sides. I may try another copy of the lens.

Your results will be sharper at 1m than 0.7m if you pixel peep but the lens has floating elements so it is supposed to perform well at the MFD.

Edit: I realize we are far from apo lenses here... Sorry for the OT folks.

Edited March 28, 2021 by lct

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Hallo,

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[hdmesa]

1 minute ago, lct said:

Your results will be sharper at 1m than 0.7m if you pixel peep but the lens has floating elements so i is supposed to perform well at the MFD.

Yes, the M10-R does allow "peeping" much farther when looking at 100% magnification. I have also been spoiled by the CV APO lenses – they are an entirely different level of detail and sharpness. But the CV APO of course do not have the amazing bokeh of the 50 Lux.

[lct]

1 minute ago, hdmesa said:

they are an entirely different level of detail and sharpness

Did you compare at f/2? I did not find such a difference with my 'Cron 50/2 apo. But the latter has less field curvature obviously.

[hdmesa]

Just now, lct said:

Did you compare at f/2? I did not find such a difference with my 'Cron 50/2 apo. But the latter has less field curvature obviously.

At f2, the Lux is really sharp, but not as sharp as the CV 50 APO. Maybe I see a little more difference since I'm looking at them on the M10-R at higher res.

Where the CV APO was MUCH better than the 50 Lux was at infinity with both stopped down to f/5.6. The detail and microcontrast of the APO is just stunning. The Lux was still good for a lens that is designed to perform better at mid distance. The Lux did have soft/smeared corners at infinity at f/5.6, but I'm talking about the very smallest piece of the corner when zoomed in to 100% on the M10-R. The CV APO may have a slightly larger image circle.

[lct]

Hard to compare f/1.4 with f/2 lenses. A 50/1.4 apo would be huge i suspect, at least too big for my taste.