What are Your experiences about sharpness so far ? at DVinfo.net

Peter Rixner · October 16th, 2005, 12:50 PM

Hello :)

OK. Not the best Title ... but let me explain:

Using the Z1 since may and still beeing really happy with it, I'm slowly getting a overview of what is possible, what not and how to improve things.

Compared with "real" HD from scanned Film and the bigones in Digital Filmmaking we're of course still far away when it comes to resolution and overall picture quality. So what are the main points:

1. The Lens
It's a nice zoom-lens that cost not even 10% of the big ones. So what is the overall recommendation for it. I guess the theoretical "best" point is exactly 50% zoomed in. Is it the similar for full tele or full wide in getting red and green Color artifacts and overall sharpness ? What are Your experiences about that ?

2. The Exposure
I would say it's good to always use the smallest f-stop. Alway keeping the lens open. To archive that I use of course the built in NDs as well (on a sunny day) further external NDs from Tiffen. I think the overall image gets worse, the higher the f-stop is. Some indicator is that there is a limit, that let's you limit the auto-exposure on certain f-stops. So what's Your opinion on that ?

3. The Shutter
Somehow, this belongs more to Point 2.
If internal ND-Filters are to weak I think it's good increasing the shutter to keep the f-stop small for better image quality.
Or is it even better than ND at all ? I guess not, as you need so high shutters, that everything gets "shuttery" :)
But for normal situations maybe not more the 100 or so. Did you get similar results ?

All in all:
I am aware of the link between all that an the depth of field. But I guess that even more speaks for always keep the f-stop as small as possible, to get the lowest depth of field you can expect from a 1/3".

So every thought or idea could help all of us to improve the imagequality of this wounderful tool.

Peter :)

Tom Roper · October 16th, 2005, 09:16 PM

1.) Pretty much irrelevant from what I've seen, the zoom point. A small amount of purple fringing, no red/green artifacts observed.

2.) f/5.2 is about the center of the sharpness range of the aperture, with not much softening from about f4.0, not much diffraction until about f8.0. In the picture profile setting, I set the f-stop to not go higher than f/6.8 numerically.

3.) For maximum resolution, I set it for aperture priority at f/5.2, then choose whichever of the two built in ND filters gets me closest to the shutter speed I want.

The Z1 doesn't look far behind broadcast HDTV on resolution and video picture quality to me. For 24 fps, that's not my area of interest but the Z1 is probably not the best choice for film making.

Peter Rixner · October 17th, 2005, 05:27 AM

Thanks for Your answers.

Do I get You right, that f/5.2 is sharper than the most possible f-stop ?
I thought it better to keep it open as possible (for video-cameras in general)

Thanks!

Peter :)

Tom Roper · October 17th, 2005, 08:57 AM

All factors being equal, a lens is usually sharpest at the middle to high f/stop settings because the exposure is from the center part of the glass where the light rays are bent the least.

At the lower f/stop settings, the iris opens up gathering imaged light from around the edges of the lens where it is bent more.

From the standpoint of the lens alone, it is usual for it to be sharpest toward the higher f/stop settings, but you have to consider the image taken in total with the effect of the iris, which is to bend the light at the edge of the iris due to diffraction. This scatters light, and the impact is more noticeable as the iris becomes smaller.

So the combined influence of the iris taken together with the lens usually results in a maximum resolution in the middle part of the f/stop range.

Peter Rixner · October 17th, 2005, 09:32 AM

Thanks again.
That sounds very interesting and seems to be even more complex than I expected :)

Is there a good website, that explains all those thing with recommendations for practical use ? I really would like to get more info about that.

Peter

Jon Ching · October 17th, 2005, 11:04 AM

What's your experience with the sharpness adjustments in the picture profile setting? With trees or leaves in a wide shot, it seems better with reduced sharpness - half-way or less. Closeups of things with less textural detail seems to do well with higher settings but it's hard to tell from either the eyepiece or lcd image when in the field. I'm trying to evaluate these images on hdtv crt and was wondering what people with good hd monitors thought.

Chris Jothi · October 18th, 2005, 04:11 PM

With the f stop in the middle you are increasing your depth of field though. So really you should consider what effect you want as opposed to thinking which F stop will be sharpest.

The reason I say this is because the difference in sharpness between f stops is less significant than the difference in DOP between apertures, which I would argue is more important.

It's not like F1.6 is soft! Yes F5 (or whatever) IS sharper, and when I do not want a shallow DOP will also get it to that point, but is it something the audience will really be able to notice? The difference in DOP between F stops 1.6 and F5 is however very noticeable.

Tom Roper · October 18th, 2005, 05:27 PM

There's no question that DOF represents a larger change with f/stop than resolution in most instances. But I wouldn't go so far as to make sweeping generalizations that it's always more important. It very well could be of course, but that would depend on the intent.

Even diffraction caused by a small iris opening could be used to some effect if that was the intent. But moreover, consider the example of trying to capture the rich panorama and grandeur of the Grand Canyon. You would want to use a wide angle zoom lens setting, with focus to infinity. In that circumstance, there would be extremely minimal if any influence on depth of field attributable to f/stop, but in order to capture all the detail with maximum clarity, you would choose the f/stop that was the best compromise between lens resolution and minimal diffraction caused by the iris.

In the end, it just comes down to the intent. That's what makes cams like the fx1/z1u so much fun.

Chris Jothi · October 18th, 2005, 05:29 PM

Tom, I completely agree!

Steve Crisdale · October 19th, 2005, 09:07 AM

Have you adjusted the sharpness setting in the camera menu?

If your camera has the factory default sharpness setting, it'll probably be more than you really require. Some people suggest 8-9. (0 = soft, 15 = sharpest)

There's lots of image adjustment that you'll need to learn with these cameras. How they all interact for certain qualities of video is going to be something that you'll learn with experience.

Sharpness is such a subjective thing. Take the LCD vs CRT HDTV debate for instance. Some people think LCD is too sharp, some think CRT too soft. In the end, it's personal judgement that counts.

Given the improvements in HDV editing capabilities (CFHD avi for instance), I have adjusted my sharpness setting down to 7 and use an Unsharp Mask filter in Vegas to add extra sharpness.

Augusto Manuel · October 20th, 2005, 02:38 PM

I totally agree with your posting. I was about to post something similar. This talk about which F/stop shows the sharpest picture is a bit nonsense. As a DP /cameraman, one should be more concerned about DOF rather than to determine which f-stop shows the sharpest image.

Quote:

Originally Posted by Chris Jothi

With the f stop in the middle you are increasing your depth of field though. So really you should consider what effect you want as opposed to thinking which F stop will be sharpest.

The reason I say this is because the difference in sharpness between f stops is less significant than the difference in DOP between apertures, which I would argue is more important.

It's not like F1.6 is soft! Yes F5 (or whatever) IS sharper, and when I do not want a shallow DOP will also get it to that point, but is it something the audience will really be able to notice? The difference in DOP between F stops 1.6 and F5 is however very noticeable.

October 16th, 2005, 12:50 PM	#1
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	What are Your experiences about sharpness so far ? Hello :) OK. Not the best Title ... but let me explain: Using the Z1 since may and still beeing really happy with it, I'm slowly getting a overview of what is possible, what not and how to improve things. Compared with "real" HD from scanned Film and the bigones in Digital Filmmaking we're of course still far away when it comes to resolution and overall picture quality. So what are the main points: 1. The Lens It's a nice zoom-lens that cost not even 10% of the big ones. So what is the overall recommendation for it. I guess the theoretical "best" point is exactly 50% zoomed in. Is it the similar for full tele or full wide in getting red and green Color artifacts and overall sharpness ? What are Your experiences about that ? 2. The Exposure I would say it's good to always use the smallest f-stop. Alway keeping the lens open. To archive that I use of course the built in NDs as well (on a sunny day) further external NDs from Tiffen. I think the overall image gets worse, the higher the f-stop is. Some indicator is that there is a limit, that let's you limit the auto-exposure on certain f-stops. So what's Your opinion on that ? 3. The Shutter Somehow, this belongs more to Point 2. If internal ND-Filters are to weak I think it's good increasing the shutter to keep the f-stop small for better image quality. Or is it even better than ND at all ? I guess not, as you need so high shutters, that everything gets "shuttery" :) But for normal situations maybe not more the 100 or so. Did you get similar results ? All in all: I am aware of the link between all that an the depth of field. But I guess that even more speaks for always keep the f-stop as small as possible, to get the lowest depth of field you can expect from a 1/3". So every thought or idea could help all of us to improve the imagequality of this wounderful tool. Peter :)

October 16th, 2005, 09:16 PM	#2
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	1.) Pretty much irrelevant from what I've seen, the zoom point. A small amount of purple fringing, no red/green artifacts observed. 2.) f/5.2 is about the center of the sharpness range of the aperture, with not much softening from about f4.0, not much diffraction until about f8.0. In the picture profile setting, I set the f-stop to not go higher than f/6.8 numerically. 3.) For maximum resolution, I set it for aperture priority at f/5.2, then choose whichever of the two built in ND filters gets me closest to the shutter speed I want. The Z1 doesn't look far behind broadcast HDTV on resolution and video picture quality to me. For 24 fps, that's not my area of interest but the Z1 is probably not the best choice for film making.

October 17th, 2005, 05:27 AM	#3
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	Thanks for Your answers. Do I get You right, that f/5.2 is sharper than the most possible f-stop ? I thought it better to keep it open as possible (for video-cameras in general) Thanks! Peter :)

October 17th, 2005, 08:57 AM	#4
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	All factors being equal, a lens is usually sharpest at the middle to high f/stop settings because the exposure is from the center part of the glass where the light rays are bent the least. At the lower f/stop settings, the iris opens up gathering imaged light from around the edges of the lens where it is bent more. From the standpoint of the lens alone, it is usual for it to be sharpest toward the higher f/stop settings, but you have to consider the image taken in total with the effect of the iris, which is to bend the light at the edge of the iris due to diffraction. This scatters light, and the impact is more noticeable as the iris becomes smaller. So the combined influence of the iris taken together with the lens usually results in a maximum resolution in the middle part of the f/stop range.

October 17th, 2005, 09:32 AM	#5
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	Thanks again. That sounds very interesting and seems to be even more complex than I expected :) Is there a good website, that explains all those thing with recommendations for practical use ? I really would like to get more info about that. Peter

October 17th, 2005, 11:04 AM	#6
Jon Ching New Boot Join Date: Oct 2004 Location: California Posts: 8	What's your experience with the sharpness adjustments in the picture profile setting? With trees or leaves in a wide shot, it seems better with reduced sharpness - half-way or less. Closeups of things with less textural detail seems to do well with higher settings but it's hard to tell from either the eyepiece or lcd image when in the field. I'm trying to evaluate these images on hdtv crt and was wondering what people with good hd monitors thought.

October 18th, 2005, 04:11 PM	#7
Chris Jothi Regular Crew Join Date: Feb 2005 Posts: 74	With the f stop in the middle you are increasing your depth of field though. So really you should consider what effect you want as opposed to thinking which F stop will be sharpest. The reason I say this is because the difference in sharpness between f stops is less significant than the difference in DOP between apertures, which I would argue is more important. It's not like F1.6 is soft! Yes F5 (or whatever) IS sharper, and when I do not want a shallow DOP will also get it to that point, but is it something the audience will really be able to notice? The difference in DOP between F stops 1.6 and F5 is however very noticeable.

October 18th, 2005, 05:27 PM	#8
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	There's no question that DOF represents a larger change with f/stop than resolution in most instances. But I wouldn't go so far as to make sweeping generalizations that it's always more important. It very well could be of course, but that would depend on the intent. Even diffraction caused by a small iris opening could be used to some effect if that was the intent. But moreover, consider the example of trying to capture the rich panorama and grandeur of the Grand Canyon. You would want to use a wide angle zoom lens setting, with focus to infinity. In that circumstance, there would be extremely minimal if any influence on depth of field attributable to f/stop, but in order to capture all the detail with maximum clarity, you would choose the f/stop that was the best compromise between lens resolution and minimal diffraction caused by the iris. In the end, it just comes down to the intent. That's what makes cams like the fx1/z1u so much fun.

October 18th, 2005, 05:29 PM	#9
Chris Jothi Regular Crew Join Date: Feb 2005 Posts: 74	Tom, I completely agree!

October 19th, 2005, 09:07 AM	#10
Steve Crisdale Major Player Join Date: Jan 2004 Location: Katoomba NSW Australia Posts: 635	Have you adjusted the sharpness setting in the camera menu? If your camera has the factory default sharpness setting, it'll probably be more than you really require. Some people suggest 8-9. (0 = soft, 15 = sharpest) There's lots of image adjustment that you'll need to learn with these cameras. How they all interact for certain qualities of video is going to be something that you'll learn with experience. Sharpness is such a subjective thing. Take the LCD vs CRT HDTV debate for instance. Some people think LCD is too sharp, some think CRT too soft. In the end, it's personal judgement that counts. Given the improvements in HDV editing capabilities (CFHD avi for instance), I have adjusted my sharpness setting down to 7 and use an Unsharp Mask filter in Vegas to add extra sharpness.