Can you get sharper infinity from a 50mm prime ?

bygp · 09-14-2015, 01:02 AM

I've just ended fixing a de-centered lens issue (rear block) and then re-calibrated my Auto Chinon 50mm 1.7 prime infinity focus.

As I'll use it for landscapes (but not only^^), just want to know if you feel it is well calibrated.

Here is a 100% crop centered on the focus point (hill) taken at 2.8 iso 100 with my K200D, raw mode at 1/1500 (need to open it wide for calibration), the top of this hill is about 5 Km far :

(also pictures are usualy a bit downgraded as I use LR direct publishing on flickr, no control on JPEG quality like when opening the DNG in photoshop or fireworks for total output quality)

I can get a bit sharper from my vivitar series 1 70-210mm (1st release) but it's not the same focal and aperture.

Hard to find the perfect focus because at this range, field depth is so long, buildings only 200m far seem almost as sharp, even at f2.8...

Last edited by bygp; 09-14-2015 at 02:30 AM.

Not a Number · 09-14-2015, 02:25 AM

A UV filter would possibly cut some of the blue light scatter from atmospheric effects and perhaps give you a sharper looking image. Difference in performance between lenses could also be from coatings.

Otherwise fiddle around with the infinity settings on the lens and see if you can get it sharper. Or put it on an optical bench and collimate the lens for best infinity adjustment.

Na Horuk · 09-14-2015, 02:43 AM

The building is not in focus, the mountain behind it is. Its not bad, especially if you took that photo with wide open aperture. If you use f4 or f8, you will get more DoF and a photo that appears to be sharper.
A cause of some blur could be the atmosphere itself.
Other problems could be if infinity is miscalibrated on the distance scales - if focus ring doesn't reach it, or goes past it. I suggest you put on a lens hood (or improvise one), use 2 sec timer, and use live view with zoom to focus the lens on a clear day, particularly one with low atmospheric haze (pollution, heat, particles). A day after rain is usually a good one.

bygp · 09-14-2015, 03:18 AM

Originally posted by Na Horuk

The building is not in focus, the mountain behind it is. Its not bad, especially if you took that photo with wide open aperture. If you use f4 or f8, you will get more DoF and a photo that appears to be sharper.
A cause of some blur could be the atmosphere itself.
Other problems could be if infinity is miscalibrated on the distance scales - if focus ring doesn't reach it, or goes past it. I suggest you put on a lens hood (or improvise one), use 2 sec timer, and use live view with zoom to focus the lens on a clear day, particularly one with low atmospheric haze (pollution, heat, particles). A day after rain is usually a good one.

This is the sharper I can get, I was calibrating the focus when taking this shot, this shot was a calibrating shot. I have a skylight filter and a hood but I'm reaching my CCD limitations because the cross thickness is approximately = 1 pixel when I zoom the RAW file^^ The focus is on the mountain, yes. Of course I can get sharper if I stop a bit more. And yes, the atmospheric and lightning conditions lower hill contrast, but this is what you see also with your eyes.

I'll take another shot from the same place this afternoon with exactly the same focus center, one with the 50mm and one with the Vivitar, good test to see which of lens or camera makes the limit

Anyway, converting the RAW via photoshop exporting it in 100% quality jpeg gives a better rendering, even if you don't realy control how flickr convert photos, because they do convert, even if hard to notice, same shot exported via PS :

(don't understand why PS modifies color profile although it is set as sRGB exactly as in LR, need to digg that one day...)

---------- Post added 09-14-15 at 03:26 AM ----------

Full frame (no crop) of almost the same shot (1 or 2 minutes before), you can see there were some light clouds masking the hill, only testing purpose, not photo contest

---------- Post added 09-14-15 at 03:28 AM ----------

or pollution ? erk ! :/

Last edited by bygp; 09-14-2015 at 06:40 AM.

Ray-uk · 09-14-2015, 03:39 AM

If you really want to set it up on infinity then pick a nice clear night and focus on the moon. Unfortuneately with the pictures you have shown the murky atmosphere makes it difficult to judge if it is focussed correctly, try again just after it has rained when the air is much clearer.

Some lenses are corrected better at infinity than others and it doesn't bear any relationship to the focal length just the way they are designed.

bygp · 09-14-2015, 03:59 AM

Originally posted by Ray-uk

If you really want to set it up on infinity then pick a nice clear night and focus on the moon. Unfortuneately with the pictures you have shown the murky atmosphere makes it difficult to judge if it is focussed correctly, try again just after it has rained when the air is much clearer.

Some lenses are corrected better at infinity than others and it doesn't bear any relationship to the focal length just the way they are designed.

I'm in the south of France, we had almost no rain this summer, maybe one day, I'm note sure^^ That's why atmosphere is not as clear as in other parts of the country, and being close to the sea adds humidity % + a bit of pollution from a big town... Unlike many, I'm waiting for some big stormy days, I love that !

My 2 zooms (a sigma 70-210 and a vivitar 70-210 series 1) are surely sharper for long range, they are built for that, mainly the sigma which has no macro mode. I'm pretty sure my cheap sigma can beat the vivitar even if it gives less contrast. My 2 other primes are probably less performing at infinity, as they have finer close focus and wider angles (24 & 28mm).

bygp · 09-14-2015, 07:31 AM

4 P.M. sky is more clear, I did compare the 50mm far range sharpness with 2 zooms set at 80mm and it is very close, so this Chinon is realy a nice prime lens, the prime was set at F8 and zooms set at 6.5. Still 100% crops directly published from LR untouched, only cropped.

50mm Auto Chinon MC 1.7 :

70-210 Sigma AF-K (zoom-k) :

70-210 Vivitar series 1 (1st release 67mm filer) :

In these 3 shots, inspecting the RAW file shows that sharpness limitation comes from K200D 10Mpix definition.

I still don't understand why this Sigma zoom has a so low contrast compared to my other lens, as this does not always occur, maybe a skylight filter is mandatory with this zoom ?

And to digg a bit more, the Vivitar 100% crop at 210mm :

---------- Post added 09-14-15 at 07:40 AM ----------

All were manually focused, even with the sigma because K200D AF is not always accurate for very far subjects, and here, 5 Km is quite far.

---------- Post added 09-14-15 at 07:49 AM ----------

Got this Vivitar (constant 1:3.5 aperture) for around 65$, very nice performer for the price, almost prime quality on all focal range. But HEAVY !

09-14-2015, 01:02 AM	#1
bygp Veteran Member Join Date: Aug 2015 Location: Toulon, South of France Photos: Gallery \| Albums Posts: 357	Can you get sharper infinity from a 50mm prime ? I've just ended fixing a de-centered lens issue (rear block) and then re-calibrated my Auto Chinon 50mm 1.7 prime infinity focus. As I'll use it for landscapes (but not only^^), just want to know if you feel it is well calibrated. Here is a 100% crop centered on the focus point (hill) taken at 2.8 iso 100 with my K200D, raw mode at 1/1500 (need to open it wide for calibration), the top of this hill is about 5 Km far : (also pictures are usualy a bit downgraded as I use LR direct publishing on flickr, no control on JPEG quality like when opening the DNG in photoshop or fireworks for total output quality) I can get a bit sharper from my vivitar series 1 70-210mm (1st release) but it's not the same focal and aperture. Hard to find the perfect focus because at this range, field depth is so long, buildings only 200m far seem almost as sharp, even at f2.8... Last edited by bygp; 09-14-2015 at 02:30 AM.

09-14-2015, 03:59 AM	#6
bygp Veteran Member Join Date: Aug 2015 Location: Toulon, South of France Photos: Gallery \| Albums Posts: 357 Original Poster	Originally posted by Ray-uk If you really want to set it up on infinity then pick a nice clear night and focus on the moon. Unfortuneately with the pictures you have shown the murky atmosphere makes it difficult to judge if it is focussed correctly, try again just after it has rained when the air is much clearer. Some lenses are corrected better at infinity than others and it doesn't bear any relationship to the focal length just the way they are designed. I'm in the south of France, we had almost no rain this summer, maybe one day, I'm note sure^^ That's why atmosphere is not as clear as in other parts of the country, and being close to the sea adds humidity % + a bit of pollution from a big town... Unlike many, I'm waiting for some big stormy days, I love that ! My 2 zooms (a sigma 70-210 and a vivitar 70-210 series 1) are surely sharper for long range, they are built for that, mainly the sigma which has no macro mode. I'm pretty sure my cheap sigma can beat the vivitar even if it gives less contrast. My 2 other primes are probably less performing at infinity, as they have finer close focus and wider angles (24 & 28mm). Last edited by bygp; 09-14-2015 at 04:11 AM.

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09-14-2015, 02:25 AM	#2
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	A UV filter would possibly cut some of the blue light scatter from atmospheric effects and perhaps give you a sharper looking image. Difference in performance between lenses could also be from coatings. Otherwise fiddle around with the infinity settings on the lens and see if you can get it sharper. Or put it on an optical bench and collimate the lens for best infinity adjustment.

09-14-2015, 02:43 AM	#3
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	The building is not in focus, the mountain behind it is. Its not bad, especially if you took that photo with wide open aperture. If you use f4 or f8, you will get more DoF and a photo that appears to be sharper. A cause of some blur could be the atmosphere itself. Other problems could be if infinity is miscalibrated on the distance scales - if focus ring doesn't reach it, or goes past it. I suggest you put on a lens hood (or improvise one), use 2 sec timer, and use live view with zoom to focus the lens on a clear day, particularly one with low atmospheric haze (pollution, heat, particles). A day after rain is usually a good one.

09-14-2015, 03:18 AM	#4
bygp Veteran Member Join Date: Aug 2015 Location: Toulon, South of France Photos: Gallery \| Albums Posts: 357 Original Poster	Originally posted by Na Horuk The building is not in focus, the mountain behind it is. Its not bad, especially if you took that photo with wide open aperture. If you use f4 or f8, you will get more DoF and a photo that appears to be sharper. A cause of some blur could be the atmosphere itself. Other problems could be if infinity is miscalibrated on the distance scales - if focus ring doesn't reach it, or goes past it. I suggest you put on a lens hood (or improvise one), use 2 sec timer, and use live view with zoom to focus the lens on a clear day, particularly one with low atmospheric haze (pollution, heat, particles). A day after rain is usually a good one. This is the sharper I can get, I was calibrating the focus when taking this shot, this shot was a calibrating shot. I have a skylight filter and a hood but I'm reaching my CCD limitations because the cross thickness is approximately = 1 pixel when I zoom the RAW file^^ The focus is on the mountain, yes. Of course I can get sharper if I stop a bit more. And yes, the atmospheric and lightning conditions lower hill contrast, but this is what you see also with your eyes. I'll take another shot from the same place this afternoon with exactly the same focus center, one with the 50mm and one with the Vivitar, good test to see which of lens or camera makes the limit Anyway, converting the RAW via photoshop exporting it in 100% quality jpeg gives a better rendering, even if you don't realy control how flickr convert photos, because they do convert, even if hard to notice, same shot exported via PS : (don't understand why PS modifies color profile although it is set as sRGB exactly as in LR, need to digg that one day...) ---------- Post added 09-14-15 at 03:26 AM ---------- Full frame (no crop) of almost the same shot (1 or 2 minutes before), you can see there were some light clouds masking the hill, only testing purpose, not photo contest ---------- Post added 09-14-15 at 03:28 AM ---------- or pollution ? erk ! :/ Last edited by bygp; 09-14-2015 at 06:40 AM.

09-14-2015, 03:39 AM	#5
Ray-uk Senior Member Join Date: Oct 2013 Location: Kent Photos: Gallery Posts: 159	If you really want to set it up on infinity then pick a nice clear night and focus on the moon. Unfortuneately with the pictures you have shown the murky atmosphere makes it difficult to judge if it is focussed correctly, try again just after it has rained when the air is much clearer. Some lenses are corrected better at infinity than others and it doesn't bear any relationship to the focal length just the way they are designed.

09-14-2015, 07:31 AM	#7
bygp Veteran Member Join Date: Aug 2015 Location: Toulon, South of France Photos: Gallery \| Albums Posts: 357 Original Poster	4 P.M. sky is more clear, I did compare the 50mm far range sharpness with 2 zooms set at 80mm and it is very close, so this Chinon is realy a nice prime lens, the prime was set at F8 and zooms set at 6.5. Still 100% crops directly published from LR untouched, only cropped. 50mm Auto Chinon MC 1.7 : 70-210 Sigma AF-K (zoom-k) : 70-210 Vivitar series 1 (1st release 67mm filer) : In these 3 shots, inspecting the RAW file shows that sharpness limitation comes from K200D 10Mpix definition. I still don't understand why this Sigma zoom has a so low contrast compared to my other lens, as this does not always occur, maybe a skylight filter is mandatory with this zoom ? And to digg a bit more, the Vivitar 100% crop at 210mm : ---------- Post added 09-14-15 at 07:40 AM ---------- All were manually focused, even with the sigma because K200D AF is not always accurate for very far subjects, and here, 5 Km is quite far. ---------- Post added 09-14-15 at 07:49 AM ---------- Got this Vivitar (constant 1:3.5 aperture) for around 65$, very nice performer for the price, almost prime quality on all focal range. But HEAVY !