Samyang 85mm f/1.4 Usage Note/Important tips

Started Jan 26, 2010 | Discussions
viking79
viking79 Forum Pro • Posts: 14,157
Samyang 85mm f/1.4 Usage Note/Important tips

The Samyang is very sharp stopped down, but ...

Focus using Optical Viewfinder (shows f/2 to f/2.8 approximately):
Shoot at f/1.4, Use live view or focus bracket
Shoot at f/2 to 2.8, focus using the viewfinder
Shoot at f/4 or higher, focus at f/4 using the viewfinder with DOF preview held

Tip: Use the depth of field preview button with selected aperture while focusing at apertures smaller than wide open.

Tip: Want balanced corners/edge performance? Focus at f/2.8 or so, shoot at f/4 or higher.

Focus using Live View:
Shoot at f/1.4, focus at f/1.4
Shoot at f/2.8, focus at f/2.8
Shoot at f/4, focus at f/4

Do Not: Focus at f/1.4 (which is how you usually focus) and shoot at f/4 or higher.

Tip: Use the depth of field preview button with selected aperture while focusing in live view.

Tip: Want balanced corners/edge performance? Focus at f/2.8 or so, shoot at f/4 or higher.

Reasons follow:

For Samyang 85mm f/1.4 users, I found something interesting when doing lens resolution tests with this lens. I, like several other reviewers thought the lens didn't improve as much as other lenses stopped down. The problem with each lens reviewer generally reads others lens reviews and the misinformation spreads, and most of us focus at f/1.4 (that is how the live view will focus).

I have since found this statement to be false. At f/5.6 the lens has the same sharpness as my A 50mm f/1.4, which is a very sharp lens at that aperture.

What I have found, is that if you focus at f/1.4, the lens will not be sharp at f/5.6. However, if you refocus the lens past f/2, say at f/4, the lens will be extremely sharp at f/5.6. In order to focus at different apertures, hold the depth of field preview button while focusing (live view or manual).

This is because this lens seems to have a massive focus shift at f/2.8. I should point out that when focused at f/4 with the Samyang, the image was almost unusable at f/1.4. When focused at f/1.4, the image was great at f/1.4, but so-so at f/4. I immediately noticed this issue when I saw the corners were performing above many lenses center resolutions at f/5.6. The lens must have some field curvature, so when the center is off at f/5.6 the corners were sharp.

Even though the Sigma and Samyang are about the same resolution as SMCP A 50mm at f/1.4, they produce nicer images at f/1.4 than the 50mm. They don't have as much of that purplish/bluish hue that the 50mm f/1.4 does and the overall contrast is likely higher. Here are some data charts:

The first image is a chart comparing the center MTF 50 (basically sharpness, combined resolution and contrast, resolution at which the contrast has decreased to 50%). Rokinon 85mm 1.4 is focused at f/1.4, and the version with (2) is focused at f/4. I have the Sigma 30mm f/1.4 and SMCP A 50mm f/1.4 for comparison, which were both focused at f/4 (the Sigma 30mm shows a focus shift as well, but to a much lesser degree than the 85mm).

What is also interesting, that if focused at the center at f/1.4, the focus will be sharp in the corners at f/4, but focus at the center at f/4, and the corners will not be sharp. A good point might lie in between the focus at f/1.4 and f/4. Focusing at f/2.8 might be a good idea.

And here are the same charts showing resolution (MTF10, resolution at which contrast has decreased 90%, basically blurred to nothing)

What does all this mean?

Be careful focusing the 85mm, and ironically, the viewfinder light that is about f/2 to f/2.8 is why it is terribly difficult with this lens to achieve focus at f/1.4 as the focus shift has already started to occur.

I hope this helps someone get better pictures from their Samyang 85mm f/1.4.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
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Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
writeB New Member • Posts: 5
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Solid tips. I'll definitely give this a shot and check back in.

-Mulls over if the live view tip may resolve quite a few focus issues with manual lenses in general too.

viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

writeB wrote:

Solid tips. I'll definitely give this a shot and check back in.

-Mulls over if the live view tip may resolve quite a few focus issues with manual lenses in general too.

Thanks, and I will try some real world test shots too. Test charts being flat don't show the entire picture.

I just hit the realization too. This would also be an issue even with a quality focus aid in the viewfinder (split prism), as you would be getting critical focus at f/1.4, which wouldn't be critical at f/4. The split prism would be valuable for f/1.4-2 shooting though, but above that focus should be done with the DOF preview on for a sharper picture.

I think this is the entire reason some tests show this lens as being unsharp when stepped down. The benefit of a smart lens is that the camera automatically corrects for this (I notice my K-7 automatically tweaks my Sigma 30mm f/1.4 around f/2.8 or f/4 or so.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

viking79 wrote:

writeB wrote:

Solid tips. I'll definitely give this a shot and check back in.

-Mulls over if the live view tip may resolve quite a few focus issues with manual lenses in general too.

Thanks, and I will try some real world test shots too. Test charts being flat don't show the entire picture.

I just hit the realization too. This would also be an issue even with a quality focus aid in the viewfinder (split prism), as you would be getting critical focus at f/1.4, which wouldn't be critical at f/4. The split prism would be valuable for f/1.4-2 shooting though, but above that focus should be done with the DOF preview on for a sharper picture.

I think this is the entire reason some tests show this lens as being unsharp when stepped down. The benefit of a smart lens is that the camera automatically corrects for this (I notice my K-7 automatically tweaks my Sigma 30mm f/1.4 around f/2.8 or f/4 or so.

Now, why doesn't a manufacture license this lens for auto focus use? That would make life much easier. Come on Sigma or Tamron, make one of these with AF

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
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Leuf Senior Member • Posts: 1,131
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Interesting. I tried just now with my split prism and I'm not seeing much of any shift if I focus and then dof preview at f/4 at minimum focus distance.

viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Leuf wrote:

Interesting. I tried just now with my split prism and I'm not seeing much of any shift if I focus and then dof preview at f/4 at minimum focus distance.

Thanks for the input. I notice with mine if I focus at f/4 on a real subject using live view with the DOF preview on and then let go of the DOF preview (live view now shows f/1.4, at least in a dark area) it is no longer critically sharp (but close). A tiny tweak brings it back in line.

This is one of those things that might mean more to a lens test chart than actual use. The problem is people buy lenses based on lens test chart results and not from actual photographs. A distance of 1mm of the focus ring moves a lens from critically sharp to not very sharp (say 10% of the MTF or so). On a real subject this might not make much difference.

Thanks again for the input. I didn't make it clear in my original post, but it is a hypothesis of sorts and I would like to test it. It holds for my lens test charts, but I want to make sure it holds in the real world too

Eric

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I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
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Leuf Senior Member • Posts: 1,131
Re: Samyang 85mm f/1.4 Usage Note/Important tips

It was just a look through the vf, so without having even taken a picture I'm not disputing your results. Just that nothing jumped out at me. No time to play with live view and tripods any time soon. In the last few months I've gotten the 85, Sigma 50/1.4 and a used tammy 28-75 but hardly had a chance to use any of them. But the days are slowly getting longer...

viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Leuf wrote:

It was just a look through the vf, so without having even taken a picture I'm not disputing your results. Just that nothing jumped out at me. No time to play with live view and tripods any time soon. In the last few months I've gotten the 85, Sigma 50/1.4 and a used tammy 28-75 but hardly had a chance to use any of them. But the days are slowly getting longer...

One of my favorite times of year. The days are definitely getting longer for those of us in the northern hemisphere anyway, although today still felt plenty cold.

That is a great batch of lenses to try out! I have some lenses that I am itching to try this weekend.

Eric

-- hide signature --

I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
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MightyMike Forum Pro • Posts: 41,233
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Wow great stuff... now how does it perform with the 1.7x AFA
--
Mike from Canada

'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote :)'

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MightyMike Forum Pro • Posts: 41,233
Re: Samyang 85mm f/1.4 Usage Note/Important tips

There is a rumor that Sigma is working on an 85mm F1.4, i hope they make it as good as their 50mm F1.4
--
Mike from Canada

'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote :)'

http://www.airliners.net/search/photo.search?sort_order=views%20DESC&first_this_page=0&page_limit=180&&emailsearch=mighty_mike88%40hotmail.com&thumbnails=

photogerald Senior Member • Posts: 1,798
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Eric, this is very impressive testing and the results will benefit all owners of this lens!

I've never experienced "focus shift" due to changing aperture with any of my lenses, and in fact I am curious as to the reasons behind this behaviour.

But I'm guessing the reason why it's present in this lens is probably due to some design tradeoffs, and that's why we don't often see it with more expensive lenses.

I'd also be interested in hearing about the setup you use for your MTF testing, when you have time.

Anyways, this is good info to know.

viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

photogerald wrote:

Eric, this is very impressive testing and the results will benefit all owners of this lens!

I've never experienced "focus shift" due to changing aperture with any of my lenses, and in fact I am curious as to the reasons behind this behaviour.

But I'm guessing the reason why it's present in this lens is probably due to some design tradeoffs, and that's why we don't often see it with more expensive lenses.

Usually it is caused by spherical aberration. Where the light at large apertures is focused differently than the light at smaller apertures due to lens shape. This shouldn't be much issue in aspheric lens elements though, so maybe it can be caused by other factors. I don't know yet. You can usually see spherical aberration in bokeh circles as they appear a bit like donuts, and the 85mm f/1.4 doesn't have those.

I'd also be interested in hearing about the setup you use for your MTF testing, when you have time.

Anyways, this is good info to know.

Sure, a good resource to start with is Koren's work (he founded a company called Imatest): http://www.normankoren.com/Tutorials/MTF5.html

The first thing I learned is it is time consuming and error prone to test lenses. It is important to be able to achieve good focus, and I found live view helps a lot with that, but even then it isn't close enough some times.

Lighting needs to be uniform, or at least close to it, although I have found this doesn't change the results that significantly. Currently I just illuminate the test chart I made with 2 incandescent bulbs, one from the upper right and one from the lower left.

I am shooting at a magnification of 1:50, which is pretty standard. I notice even my 60-250mm f/4 reads the correct focal length at that distance. Using the above charts I can measure the true focal length of the lens easily as well. The SMCP A 50mm f/1.4 is about 53mm, and the Rokinon 85mm is about 88mm. The Sigma 30mm f/1.4 is about 31mm. The DA 60-250mm showed correct at 88mm at that distance (about 15 ft), at minimum focus it is way off).

The main reason I started this was to compare older lenses, as the MTF data for them is often out of date or poorly done. I started testing some lenses with known characteristics so I could get a good feel for my testing. The SMCP A 50mm f/1.4 is one consistant lens. It always had similar characteristics regardless of how I tested it.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

MightyMike wrote:

Wow great stuff... now how does it perform with the 1.7x AFA
--
Mike from Canada

Too bad I don't have the 1.7 any more, but I imagine it would do fine. Focusing with that would be done on light at f/2.5 or something, so it should be a bit improved by that point. I have an old 2x converter I could try and see how it works.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

MightyMike wrote:

There is a rumor that Sigma is working on an 85mm F1.4, i hope they make it as good as their 50mm F1.4

Oh, nice, let's hope it is! Even the 30mm f/1.4 isn't bad, but it would be perfect if the corners were better. I am suspecting the 30mm was designed primarily for 4/3rds.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
photogerald Senior Member • Posts: 1,798
Re: Samyang 85mm f/1.4 Usage Note/Important tips

viking79 wrote:

Usually it is caused by spherical aberration. Where the light at large apertures is focused differently than the light at smaller apertures due to lens shape. This shouldn't be much issue in aspheric lens elements though, so maybe it can be caused by other factors. I don't know yet. You can usually see spherical aberration in bokeh circles as they appear a bit like donuts, and the 85mm f/1.4 doesn't have those.

I'm not sure if any of my lenses exhibit spherical aberration. I remember reading somewhere that some of the lenses with the most pleasing bokeh/OOF rendering have a bit of spherical aberration designed-in?

I'd also be interested in hearing about the setup you use for your MTF testing, when you have time.

Anyways, this is good info to know.

Sure, a good resource to start with is Koren's work (he founded a company called Imatest): http://www.normankoren.com/Tutorials/MTF5.html

The first thing I learned is it is time consuming and error prone to test lenses. It is important to be able to achieve good focus, and I found live view helps a lot with that, but even then it isn't close enough some times.

Lighting needs to be uniform, or at least close to it, although I have found this doesn't change the results that significantly. Currently I just illuminate the test chart I made with 2 incandescent bulbs, one from the upper right and one from the lower left.

Interesting, I didn't realize it was practical to perform MTF tests outside of a specialized testing lab.

I wonder if you can have the charts on a monitor (a good one with high resolution) and shoot that, rather than printing them out? If so, you can also use the LV moire interference patterns method to adjust fine focus. See here:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=34300658

I am shooting at a magnification of 1:50, which is pretty standard. I notice even my 60-250mm f/4 reads the correct focal length at that distance. Using the above charts I can measure the true focal length of the lens easily as well. The SMCP A 50mm f/1.4 is about 53mm, and the Rokinon 85mm is about 88mm. The Sigma 30mm f/1.4 is about 31mm. The DA 60-250mm showed correct at 88mm at that distance (about 15 ft), at minimum focus it is way off).

The main reason I started this was to compare older lenses, as the MTF data for them is often out of date or poorly done. I started testing some lenses with known characteristics so I could get a good feel for my testing. The SMCP A 50mm f/1.4 is one consistant lens. It always had similar characteristics regardless of how I tested it.

This is a good way to see how your lenses stack up against each other. Just curious, are your results consistent with published MTF tests (either in relative or absolute terms)?

Anyways, thanks Eric for the explanation.

viking79
OP viking79 Forum Pro • Posts: 14,157
Re: Samyang 85mm f/1.4 Usage Note/Important tips

photogerald wrote:

viking79 wrote:

Usually it is caused by spherical aberration. Where the light at large apertures is focused differently than the light at smaller apertures due to lens shape. This shouldn't be much issue in aspheric lens elements though, so maybe it can be caused by other factors. I don't know yet. You can usually see spherical aberration in bokeh circles as they appear a bit like donuts, and the 85mm f/1.4 doesn't have those.

I'm not sure if any of my lenses exhibit spherical aberration. I remember reading somewhere that some of the lenses with the most pleasing bokeh/OOF rendering have a bit of spherical aberration designed-in?

It creates a lot of pleasing softness, but causes other issues at well. It often works well for portraits, and soft focus lenses basically create a lot of spherical aberration if I understand correctly. With a lens with heavy spherical aberration you basically have a small range where light is in focus, it is focusing the light hitting the lens at a large angle differently than the light coming straight in (that angled light is usually stopped/blocked by the aperture diaphragm (stop) when "stopped" down.

Lighting needs to be uniform, or at least close to it, although I have found this doesn't change the results that significantly. Currently I just illuminate the test chart I made with 2 incandescent bulbs, one from the upper right and one from the lower left.

Interesting, I didn't realize it was practical to perform MTF tests outside of a specialized testing lab.

Well, you can see MTF characteristics, and you do have to be careful (so somewhat like a lab anyway). MTF of the lens alone should probably be tested in a laboratory without a camera attached. Technically I am testing both the K-7 and the lens.

One point I found is clipping blacks or highlights is dangerous and will skew the results. Clipping blacks seems to lead to sharper images than they should be. I like to verify some of the results with my eyes and comparing at 100% in Lightroom. RAW converter will also impact results, I used Lightroom with the defaults as I figure that is how most will use their lenses.

I use the same exact white balance for all photos (it is amazing how the camera picks so different white balance for different lenses, but when set the same it is pretty similar, just casts from the coatings/coloration/etc), and now check to make sure I am not clipping highlights or shadows in the test charts (I started doing this recently when I realized it made a large impact). I will release some data over the next few weeks on my blog that I have collected, and will try to make a reference web page for it.

I wonder if you can have the charts on a monitor (a good one with high resolution) and shoot that, rather than printing them out? If so, you can also use the LV moire interference patterns method to adjust fine focus. See here:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=34300658

I will share my little secret as I believe in sharing information. This actually works with a printed version of that chart and live view I used the circular ring pattern that is in the second link. Works wonderfully. You will see the moire appear on the LCD of the camera. Much, much easier than focusing using live view normally or the viewfinder.

This is a good way to see how your lenses stack up against each other. Just curious, are your results consistent with published MTF tests (either in relative or absolute terms)?

Relatively my results seem lower than Photozone.de, but the lenses seem to have similar characteristics, and the resolutions are similar to others using the same charts. I cross compare on photozone too. I do use a computer to calculate my MTF instead of using my eyes too.

The 1951 standard chart that most use is human read who will probably strain to see the sharpest pattern, etc (not saying this is bad, just don't compare MTF numbers from different sources, or use some common lens like the 50mm f/1.4 to do so).

I am working to make sure my numbers are consitant and meaningful, which is why I haven't released much data yet. I just did a comparison between the SMCP 60-250mm f/4, Tamron 70-210mm f/3.8-4, and Vivitar 100-200mm f/4 (old M42 lens full of fungus) and the results are fairly surprising, but the DA* is certainly the best in the corners, especially for resolution. All done at about 100mm.

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
Stephen Merola Contributing Member • Posts: 551
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Thanks for these tests. I can't wait to get home and test my Rokinon.
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photogerald Senior Member • Posts: 1,798
Re: Samyang 85mm f/1.4 Usage Note/Important tips

viking79 wrote:

I'm not sure if any of my lenses exhibit spherical aberration. I remember reading somewhere that some of the lenses with the most pleasing bokeh/OOF rendering have a bit of spherical aberration designed-in?

It creates a lot of pleasing softness, but causes other issues at well. It often works well for portraits, and soft focus lenses basically create a lot of spherical aberration if I understand correctly. With a lens with heavy spherical aberration you basically have a small range where light is in focus, it is focusing the light hitting the lens at a large angle differently than the light coming straight in (that angled light is usually stopped/blocked by the aperture diaphragm (stop) when "stopped" down.

Thanks for your detailed explanation on spherical aberration and why it might be desirable in certain applications.

Well, you can see MTF characteristics, and you do have to be careful (so somewhat like a lab anyway). MTF of the lens alone should probably be tested in a laboratory without a camera attached. Technically I am testing both the K-7 and the lens.

Yes, that's right - you are testing the lens plus all the components in the K-7 system (microlens, sensor, demosaicing/processing, etc.).

One point I found is clipping blacks or highlights is dangerous and will skew the results. Clipping blacks seems to lead to sharper images than they should be. I like to verify some of the results with my eyes and comparing at 100% in Lightroom. RAW converter will also impact results, I used Lightroom with the defaults as I figure that is how most will use their lenses.

I appreciate your careful approach, as otherwise the results would be less meaningful or even misleading.

I use the same exact white balance for all photos (it is amazing how the camera picks so different white balance for different lenses, but when set the same it is pretty similar, just casts from the coatings/coloration/etc), and now check to make sure I am not clipping highlights or shadows in the test charts (I started doing this recently when I realized it made a large impact). I will release some data over the next few weeks on my blog that I have collected, and will try to make a reference web page for it.

This does sound like a lot of work. I look forward to seeing your results.

Your note about white balance variation due to lens colour rendering/casting is something I've always wondered about. It should be fairly easy to test (just use a standard WB preset, such as daylight), so I've added it to my list.

I wonder if you can have the charts on a monitor (a good one with high resolution) and shoot that, rather than printing them out? If so, you can also use the LV moire interference patterns method to adjust fine focus. See here:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=34300658

I will share my little secret as I believe in sharing information. This actually works with a printed version of that chart and live view I used the circular ring pattern that is in the second link. Works wonderfully. You will see the moire appear on the LCD of the camera. Much, much easier than focusing using live view normally or the viewfinder.

This is good to know! Focus accuracy is critical when performing this types of tests, and AF can be surprisinly inaccurate (especially with fast lenses), so careful MF is the way to go.

This is a good way to see how your lenses stack up against each other. Just curious, are your results consistent with published MTF tests (either in relative or absolute terms)?

Relatively my results seem lower than Photozone.de, but the lenses seem to have similar characteristics, and the resolutions are similar to others using the same charts. I cross compare on photozone too. I do use a computer to calculate my MTF instead of using my eyes too.

The 1951 standard chart that most use is human read who will probably strain to see the sharpest pattern, etc (not saying this is bad, just don't compare MTF numbers from different sources, or use some common lens like the 50mm f/1.4 to do so).

Being able to use your computer to analyse the results will elminate one source of variation/error from your testing.

I am working to make sure my numbers are consitant and meaningful, which is why I haven't released much data yet. I just did a comparison between the SMCP 60-250mm f/4, Tamron 70-210mm f/3.8-4, and Vivitar 100-200mm f/4 (old M42 lens full of fungus) and the results are fairly surprising, but the DA* is certainly the best in the corners, especially for resolution. All done at about 100mm.

Why do you say the results were surprising? Did the old lenses measure better than you had expected?

Again, it will be very interesting to see your results. With your published results and testing procedure, perhaps we can all participate in testing our lenses. And by also comparing the results from testing a "standard" lens (such as any of the Pentax 50/1.4's), we could determine if it's valid to compare testing results from different users (but the same camera model would have to be used).

Cheers!

Thanks!

viking79
OP viking79 Forum Pro • Posts: 14,157
Updated Lens Charts

Here are my updated charts with a better setup. My usage notes still hold true for this lens.

If shooting f/1.4 to f/4 focus at the aperture you want to shoot. That means holding the optical depth of field button while you focus (live view or not). If shooting at f/4 or higher focus at f/4 by setting the lens to f/4, holding the depth of field preview, and then change the aperture to the f/stop you are using.

For example, in these charts, focused at f/4 and shot at f/1.4 put the LW/PH at 370. Focusing at f/1.4 puts it at 1000 or so. Even f/2.8 to f/4 is a big difference, about 25%. These charts present the data for best focus, so a shot focused and shot at f/4, might not have the center and corner performance shown, but shows what the lens will do if focused at that given spot.

F/2.8 looks like a good compromise for general use. You get the benefit of a large aperture with the ability to focus using the viewfinder. Even though f/1.4 is low resolution, it still works well when you don't need the high resolution (like for available light portraits, etc).

Eric
--
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be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

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Brentliris Veteran Member • Posts: 4,194
Re: Samyang 85mm f/1.4 Usage Note/Important tips

Thanks for the info! Though I don't own this lens, it puts some things in perspective about focus problems with 1.4 lenses generally I suspect. Also UW have similiar voodoo going on with the curvature of field and nearfield objects..

Regards

Brent
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For me photography is a tool for capturing these insights, for reflection and
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