Focussing Monochrom with filters

[AlanG]

Advertisement (gone after registration)

BTW I'd suggest that anyone new at using filters on b/w read Ansel Adam's "Natural Light Photography."

 

Well what I learned from this is the shadows of my posted images are pure black when viewed on my calibrated monitor in Firefox. However when I cut the image out and past it in my retouching software, it has a bit more (noisy) shadow detail. And in either program, I can actually see into the shadows on my laptop although they are very noisy. So I need to turn the brightness down on it a bit. I can't say I learned anything about using filters but see there is some inconsistency here that I did not expect.

 

This is how they look on my laptop. (I just opened up the shadows and it is surprising how much detail was there even in a jpeg.) It shows how variable our viewing situations are when using computers which may discount some of what people say when critiquing photos.... calling them too noisy.

 

Also one can clearly see that when using the red filter, the resolution drops due to only having 1/4 the pixel count and is more jagged. It supports my opinion that the interpolation up of all three channels does provide considerable detail to a b/w image that is shot without a filter... as it makes use of detail from all the pixels. So I question if the resolution benefit of an MM over an M9 is as significant as some might hope as long as one does not use individual channels from the M9 for b/w conversions.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[tom0511]

For fun I shot some images with the MM and a 50/1.4 asph from approx 1.5m distance at f1.4 and f4.0. First without filter and then with yellow-orangefilter, on a tripod without changing focus.

 

Subject was a black and white focus test chart. At daylight.

 

I did several shots and could not detect focus shift when mounting the filter.

 

However I do have the impression that the images with filter might be slightly less sharp overall.

[AlanG]

 

I wondered about this but to be blunt, if filter thickness was the problem then surely using any filter should create some visible degradation?

 

No doubt something is wrong with the tests but I very much doubt that the conclusions are correct.

 

It isn't the thickness of the glass. I am guessing that his filter is not perfectly flat.

 

Achromatic correction has been around for about 250 years. And despite the term "apo" being rather loosely used on some lenses, I would be surprised if one can find any good modern general purpose lenses that shift the red focus much.

 

Perhaps this is an example of photographic cold fusion?

[AlanG]

However I do have the impression that the images with filter might be slightly less sharp overall.

 

If you look at my shot through the red filter and compare it with the image of the red channel alone, there seems to be a very slight difference in detail. (Noticeable in "W. Eugene Smith.") I used a 72mm Hoya filter that possibly could benefit from being cleaned. Shutter speed was longer for the filtered shot so maybe vibration came into play. The exposure is slightly different and that could also be a factor in how the raw conversions and/or jpeg process works. The effect of the filter on overall sharpness would be another thing to test but it doesn't look significant enough to worry me in general use. Perhaps if I was stopped down more the difference would be greater as the image would be a bit more detailed in the first place.

[pico]

So why is Lloyd making such an issue out of it?

 

I think he is losing his mind.

 

Red light is low-frequency and will naturally resolve less than blue light, but at the scale of our work, and with modern lenses it is not that significant.

[Guest Holy Moly]

BTW I'd suggest that anyone new at using filters on b/w read Ansel Adam's "Natural Light Photography."

 

Well what I learned from this is the shadows of my posted images are pure black when viewed on my calibrated monitor in Firefox. However when I cut the image out and past it in my retouching software, it has a bit more (noisy) shadow detail. And in either program, I can actually see into the shadows on my laptop although they are very noisy. So I need to turn the brightness down on it a bit. I can't say I learned anything about using filters but see there is some inconsistency here that I did not expect.

 

This is how they look on my laptop. (I just opened up the shadows and it is surprising how much detail was there even in a jpeg.) It shows how variable our viewing situations are when using computers which may discount some of what people say when critiquing photos.... calling them too noisy.

 

Also one can clearly see that when using the red filter, the resolution drops due to only having 1/4 the pixel count and is more jagged. It supports my opinion that the interpolation up of all three channels does provide considerable detail to a b/w image that is shot without a filter... as it makes use of detail from all the pixels. So I question if the resolution benefit of an MM over an M9 is as significant as some might hope as long as one does not use individual channels from the M9 for b/w conversions.

 

Alan,

 

do you see the nasty 'aura' around the title 'Minamata' in the pic with the red filter? The name of the photographer is hardly visible, but what kind of physical influence is doing this?

 

The same phenomenon I could see in RFF. Some shots in Bangkok show the same effect, some kind of halo, not white but gray. What is it?

[AlanG]

Advertisement (gone after registration)

Alan,

 

do you see the nasty 'aura' around the title 'Minamata' in the pic with the red filter? The name of the photographer is hardly visible, but what kind of physical influence is doing this?

 

The same phenomenon I could see in RFF. Some shots in Bangkok show the same effect, some kind of halo, not white but gray. What is it?

 

It is aliasing of the edges magnified via interpolation and shouldn't have much to do with the filter. Once you are at the pixel level the edges break up. All of the edges have this but it is easier to see on a dark background. The shot without the filter has four times as many pixels to use to form those lines. If I re-post the image at 50% of this size, they should look about the same. For some reason the aliasing on the red filter shot looks a little worse than just the red channel image. But I think this has mostly to do with the difference in exposure showing it up a little more in the dark areas. I was not very scientific in my testing. I just wanted to see if the filter shifted focus at all and it didn't. Heck I didn't even bother to clean the filter and I probably hadn't looked at it in 10 years or so. I only spent about a minute on shooting the photos as it was obvious in magnified live view that it was sharp either way.

 

BTW I stumbled upon this comparison between the D800 and the 5DIII of magnified live view. So it seems that not everyone using magnified view is working with the same tool.

 

Magnification - "Ross - in the video they are identical, but the fact is that it doesn't matter. At any zoom level both for the lens or the digital zoom for live view, the D800 is significantly worse than the 5D Mark III." So it will be interesting to see how this works on the new M.

 

http://www.ronmartblog.com/2012/05/fail-nikon-d800-live-view-vs-canon-5d.html

 

Play the video he includes.

[glenerrolrd]

Having a POV does not change the laws of physics. Having a paid site does not make one an expert. The physics of light is well know to many here. It has not changed because of new technology.

 

If Lloyd proposes something that appears to violate the physics of light, we should understand why first, before we discuss how to correct. I believe the other forum members have stated the case against clearly.

 

Wow this is similar to a political debate . You missed my point entirely .

 

When I read a test report from a person that has shown to be reliable and puts forth an effort in his testing beyond anecdotal experience ......first I seek to understand how he came to the conclusions . I don t start with DL s POV makes no sense .

 

It is always possible that I ve misunderstood what DL presented ..but I have seen no response that shows that someone has read his article and feels I am off in my restatement .

 

I made no suggestion on how to deal with the focus shift he describes ..so where did that come from.

 

Rather my conclusion was that the focus shift he describes may or may not even be relevant depending on the type of photography you might be doing . There is no question that he utilizes sensational overstated headlines to draw readers. Personally I feel he cheapens his website and loses credibility . No argument on that aspect .

 

What I am reacting to is a consistent dismissal of viewpoints that might be controversial .

 

I ve shot plenty of film with filters of all types and I never saw any focus shift ...but film can be more foregiving than a 18MP B&W sensor . Will not be the first time I find issues that were just not apparent on film or at lower resolutions .

[AlanG]

He states this on his blog but I have never seen anything to substantiate it:

 

"Red/green/blue light all focus slightly differently, slightly meaning 1-2 feet differently at 15 feet of distance even with a well corrected lens! This has been true since the discovery of optics. It is always true, always has been true, always will be true, and unless the lens is a true superachromat like the Coastal Optics 60/4 UV-VIS-IR APO-macro, "

 

So what was all of that stuff about combining crown and flint glass elements since the 1700s about? (At least to get red and blue focused at the same spot with green close.)

[pico]

He states this on his blog but I have never seen anything to substantiate it:

 

"Red/green/blue light all focus slightly differently, slightly meaning 1-2 feet differently at 15 feet of distance even with a well corrected lens! This has been true since the discovery of optics. It is always true, always has been true, always will be true, and unless the lens is a true superachromat like the Coastal Optics 60/4 UV-VIS-IR APO-macro, "

 

So what was all of that stuff about combining crown and flint glass elements since the 1700s about? (At least to get red and blue focused at the same spot with green close.)

 

Exactly! In fact, I have that quote in my buffer and was about to post it.

 

That is the kind of text-byte that begs to join the panic chasers to market. And what is his advantage to promoting the Coastal Optics thing? Exactly how is that lens used in general? Will he put it up against general purpose lenses that matter in Real Life?

 

In my experience, using a deep red filter diminishes overall crispness because it permits only low-frequency light. That's all about acutance, perceived sharpness.

 

He's losing his mind.

.

[AlanG]

Exactly! In fact, I have that quote in my buffer and was about to post it.

 

That is the kind of text-byte that begs to join the panic chasers to market. And what is his advantage to promoting the Coastal Optics thing? Exactly how is that lens used in general? Will he put it up against general purpose lenses that matter in Real Life?

 

In my experience, using a deep red filter diminishes overall crispness because it permits only low-frequency light. That's all about acutance, perceived sharpness.

 

He's losing his mind.

.

 

Yes of course.

 

And it only takes less than a minute and a red filter for just about anyone to disprove this as I have shown. Heck you don't even need the filter, just split the color channels of any of your photos and see if the red one is all out of focus. How could he explain that?

[tom0511]

I guess Loyd is the contrast to Steve Huff. Stefe Huff loves every camera and Loyd searchs in the pixels until he finds something wrong / something which eventually theoreticaly could become a problem.

If I understand right it is not possible to accuratly focus a cherry tree with any camera (except you have ths one and only apo lens)...because you can either focus on the cherries or focus on the green?

[swamiji]

 

What I am reacting to is a consistent dismissal of viewpoints that might be controversial .

 

 

I am not sure that people are dismissing controversy, just his findings.

 

It appears that His controversy is self promotion.

[Woody Campbell]

2400 actuations into my MM shooting mainly wide - roughly half the shots filtered using B+W 022 (lightish yellow) or 040 (yellow orange) or the Heliopan equivalent I haven't noticed any focus issues. I'm have great respect for Lloyd but if I'm in a situation where I'm shooting at full aperture where focus gets critical I'm probably taking the filter off anyway.

[luigi bertolotti]

He states this on his blog but I have never seen anything to substantiate it:

 

"Red/green/blue light all focus slightly differently, slightly meaning 1-2 feet differently at 15 feet of distance even with a well corrected lens! This has been true since the discovery of optics. It is always true, always has been true, always will be true, and unless the lens is a true superachromat like the Coastal Optics 60/4 UV-VIS-IR APO-macro, "

 

So what was all of that stuff about combining crown and flint glass elements since the 1700s about? (At least to get red and blue focused at the same spot with green close.)

 

... one that pretends to be an expert and documented reviewer and writes the above numbers WITHOUT any other detail has really lost his mind : math is a serious science and reading numbers out of any context which can explain WHY they are correct, is always annoying and makes to think of bloating data for self promotion.

[brianv]

When I get the M Monochrome, I'll have to try this with a highly color-corrected Achromat and with one that shows more shift.

 

How can you tell the difference?

 

Look for the Infrared Focus Index on your lens. On the original Summicrons, it is within the F2 DOF marks. This "typically" means the deviations from the zero-crossings of the two corrected wavelenghts for the Achromat is low. On a Sonnar, it is closer to F4: the dispersion is greater.

 

APO lenses often do not have an IR focus index. A Super-Achromat such as the Pentax 85/4.5 is corrected for 4 wavelength crossings, into the Infrared. Maybe I can mount it in a 85/2 Nikkor focus mount for a test. The original cost of this lens was $1400 in 1970. Inflation corrected, about the same as the APO-Summicron.

[AlanG]

As demonstrated, all you have to do is split the color channels of any of your images and look for differences in sharpness between them. RGB shots are already made through filters so you can compare a lot of lenses at various distances and f stops pretty easily without doing any new shooting at all. I'd be surprised if anyone finds noticeable differences in general photography.

 

Testing on an MM will require more work and the use of filters, so testing variability and the flatness of the filters will come into play there.

[IkarusJohn]

None of my Leica lenses have the IR focusing mark.

[Advertisement]

Hallo,

Look here: Leica M

[mjh]

As demonstrated, all you have to do is split the color channels of any of your images and look for differences in sharpness between them.

It isn’t quite as simple. There are twice as many green sensitive pixels than red or blue sensitive ones, so resolution and sharpness in the green channel will, as a rule, be the highest. Focusing is calibrated for green. When the image is less sharp in the red or blue channels than it is in the green channel, is that because of a wavelength-dependent focus shift or because there are only half as many red or blue sensitive pixels?

[AlanG]

It isn’t quite as simple. There are twice as many green sensitive pixels than red or blue sensitive ones, so resolution and sharpness in the green channel will, as a rule, be the highest. Focusing is calibrated for green. When the image is less sharp in the red or blue channels than it is in the green channel, is that because of a wavelength-dependent focus shift or because there are only half as many red or blue sensitive pixels?

 

Perhaps I should have used the word "focus" instead of sharpness. I think I already stated that there is pixel count discrepancy issue in my posted examples. But even if you can't judge maximum sharpness, you generally can see if the focus has moved forwards or backwards significantly... well before going to 100%, as long as you are not examining a photo of a flat subject. Split the channels of all of those angled ruler shots people have from their rangefinder calibration tests.

 

Let's be realistic here, these very tiny differences (if they even exist in a way that could be detected using an MM but not via an M9) will be irrelevant in the kinds of general photography done with Leicas. What Lloyd was talking about was the focus being shifted a foot or more at 15 feet. In any case, if we are getting this wonky about it, a filter over the lens might degrade the image a bit too so what you are comparing will be two very slightly different optical systems, not just the way the lens focuses the colors of the light.