[Anvh]

Wow. I hope people who are just starting to delve into the super magic fun of photography don't stumble across this thread.

Photography always have been for the large part science, it's not magic that makes a photo appear
First it was only chemicals but with digital we also have electronics.

[Digitalis]

Electromagnetic radiation further into the IR region will also travel through the lens and possibly cause the above mentioned problems.

There is a limit to how sensitive and how far a cmos sensor like the one used in the K5IIs can see into the NIR spectrum - According to DALSA:

"To image in the near infrared (700 to 1000nm), imagers need to have a thicker photon absorption region. This is because infrared photons are absorbed deeper than visible photons in silicon. Most CMOS imager fabrication processes are tuned for high volume applications that only image in the visible. These imagers are not very sensitive to the near infrared (NIR). In fact, they are engineered to be as insensitive as possible in the NIR. Increasing the substrate thickness (or more accurately, the epitaxial or epi layer thickness) to improve the infrared sensitivity will degrade the ability of the imager to resolve spatial features...."

The light transmission of the R72 filter is 50% at 720 nm [B]. So, some tail of the visible light will still form the final image (the viewfinder is not totally black). Electromagnetic radiation further into the IR region will also travel through the lens and possibly cause the above mentioned problems. A strong UV/IR cut filter now blocks light with such "problematic" wavelengths [C]. Red/IR sensitivity is reduced and only "less critical" light is captured. This explains why image quality can be increased and hotspots may disappear. So, without further knowledge, I would attribute this effect to the presence of a strong UV/IR cut filter.

A well researched explanation, there is also a much simpler explanation for the reason hotspots aren't such an issue on the K5IIs - with the AA filter removed there is one less element in the optical path from which IR light can reflect from and cause hotspots and internal reflections. The presence of hotspots is notably affected by lens design, the DA12-24mm f/4 ED ASPH does suffer from a well documented hotspot issue. Unfortunately I do not own a DA12-24mm f/4, so I am unable to verify if there is any improvement in image quality in the NIR spectrum on the K5IIs with this particular lens

[froeschle]

Avoidance and elimination of hot spots (unfortunately in German):
They claim that the coatings get worse in the IR regime for longer wavelengths, which is the central issue.
Often, hot spots appear to be bluish.
This is a result of the dyestuff used in the Bayer pattern.
Red, green and blue dye have different IR transmission properties.
As a result, reflections from the most problematic IR range are mainly located in the blue channel.
Their advice:

• Hardware:
  Use a slight IR-cut filter in addition to the R72 (to suppress higher wavelength light).
  They recommend Schott KG2 or Schott KG3 glass.
• Software:
  Modify the blue channel, e.g. only use the red and green channels for your picture and swap channels RGB -> RGR, RGG, GRG

On the other hand, if the hot spot would be caused by reflections from the sensor, a strong IR cut filter might even enhance the problem.
IR blockers seem to use a dichroic mirror in combination with an IR absorbing layer.
Digital IR Choices: "in cameras with an anti-aliasing filter, the IR-blocking filter is usually integrated into that piece of glass"
It would be interesting to see how this is realized in the K-5 II and the K-5 IIs.
Wikipedia claims that "When the IR blocker is removed, many lenses which did display a hotspot cease to do so".

IR film could help to identify the source of the main problem.

However, hot spots can be an issue even with IR modified cameras.

I own an IR modified *istDL (IR-blocking filter was replaced by a Schott RG830 filter), which I seldomely use.

[Digitalis]

Avoidance and elimination of hot spots (unfortunately in German): They claim that the coatings get worse in the IR regime for longer wavelengths, which is the central issue.

Das ist nicht eine problem, Ich spreche deutch. I agree most coatings are designed for Visible light - the DA15mm f/4 ED ASPH Limited loses its legendary flare tolerance when used with a Hoya RM90 Filter.

"When the IR blocker is removed, many lenses which did display a hotspot cease to do so".

yes that is indeed the case, I own a Leica M8 - which due to an unintentional oversight has a very weak UV/IR filter, and Leica lenses that exhibit hot spots when used for IR work on the M9 do not exhibit hot spots to the same degree with the M8 - the Leica 21mm f/1.4 Summilux-M ASPH is the worst culprit for this effect. I do not use my range finders often for IR work because focusing accurately is rather challenging when you aren't looking through the lens like you do with a DSLR - also Leica M digital rangefinders do not have live view ( well until the new digital M comes out)

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Last edited by Digitalis; 03-07-2013 at 09:09 AM.

[Nass]

Wow. I hope people who are just starting to delve into the super magic fun of photography don't stumble across this thread.

Priceless

[cadart]

Photography always have been for the large part science, it's not magic that makes a photo appear
First it was only chemicals but with digital we also have electronics.

Thanks for the lesson but I have spent a number of years in a homemade darkroom with lots of yummy chemicals and yes I am aware that digital is fairly Dependant on electronics. I just made an observation that newbies to photographics would most likely politely walk away and take up a new hobby like toe-nail clipping if they happened to stumble upon this thread.

[falconeye]

the kit lens at 28 mm produces an MTF of 2604 @ F8 tested on photo zone. ...
SO at least for Pentax, if you have the kit lens, the only possible way to increase your MTF is to go filterless. But I've yet to see any numbers indicating that going filterless increases MTF on a K-5.

8%? AN 8% increase in MTF numbers? How does removing a filter give you 8% more pixels?

This is an example of sloppy use and an incomplete understanding of the acronym mtf and what it stands for. Mtf stands for "modular transfer function", better denoted mtf(f).

The figures published by photozone are f=f_50 where mtf(f_50)=0.5 (also sometimes f_50 is abbreviated as MTF50) after heavy sharpening. The sharpening is choosen such that the numbers get close to the nominal number of pixel lines. A priori, MTF50 figures after sharpening can be both higher or lower than the number of pixel lines.

In short, MTF50 and number of pixels have little in common.

The resolution of a lens is typically measured as mtf(f_5)=0.05 (abbreviated MTF5) on an optical bench. Sharpened MTF50 figures are no good way to predict optical MTF5 figues. Some sites, as a compromise, sharpen less and publish MTF20 values.

In order to understand the impact of the removal of a Bayer-AA filter (or of using a different lens), the change in the entire mtf curve must be considered. photozone MTF50 figures are only useful when far away the "peak" area (corners and wide apertures).

This is only meant as a reminder. I don't think we should discuss this topic within this thread again. I certainly won't.

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Last edited by falconeye; 03-11-2013 at 08:26 AM.

[woodywesty]

Wow. I hope people who are just starting to delve into the super magic fun of photography don't stumble across this thread.

On the contrary, I'm just learning the new electronic imaging technology and this is fascinating. Granted I'm not picking all of it up but it is a great learning opportunity. Nice to see a discussion using data derived from solid analysis along with differences of opinion based on how others view the problem. Just good science! However at some point its somewhat like debating on which of two beautiful women are the more beautiful. There just isn't an answer, What we need to do is to enjoy these two wonderful Pentax tools and go create beautiful images with them..

Long live the Pentax Forum !

Woodywesty

[cadart]

On the contrary, I'm just learning the new electronic imaging technology and this is fascinating. Granted I'm not picking all of it up but it is a great learning opportunity. Nice to see a discussion using data derived from solid analysis along with differences of opinion based on how others view the problem. Just good science! However at some point its somewhat like debating on which of two beautiful women are the more beautiful. There just isn't an answer, What we need to do is to enjoy these two wonderful Pentax tools and go create beautiful images with them..

Long live the Pentax Forum !

Woodywesty

Yes but if you were involved in this particular discussion about girls I reckon we would all end up gay

[Digitalis]

at some point its somewhat like debating on which of two beautiful women are the more beautiful

The K5II would be the beautiful woman that would be inclined to ask if those jeans made her look fat, the K5IIs needs no validation and already knows it looks awesome.

[daveej]

guess i'm not surprised this thread has come to this

[cadart]

guess i'm not surprised this thread has come to this

It was bound to happen

[dickymastelero]

Hey guys,

Just thought I'd link to this comparison we just ran at digitalcamerainfo.com. We took the K-5 II and K-5 IIs out and shot the same scenes with the same lenses and shooting parameters, then compared 100% crops (JPEG and RAW). A few other sites have done this, and it's not a super-technical comparison, but more data is always nice, right? Anyway, enjoy:

The S Is for Subtle: The Pentax K-5 II and K-5 IIs, Head to Head - DigitalCamerainfo.com

Always wanted a K-5IIs for a back up for my K-5 but settled with the K-5II. I've tested both the K-5II and IIs and I really like the sharpness of the K-5IIs, hands down for image quality. The reason I settled for the K-5II is not because its $100 cheaper but for preference of what I shoot. I shot a lot of portraits of people, events and Landscapes with my K-5 and already very happy with the excellent results I get from it, mentioning that all my lenses are Pentax Prime lenses (fixed focal and zoom lenses).

The only feature that the K-5 lacks is better AF in low light which the K-5II/IIs steps in with a -3EV sensitivity in AF compare to -1EV with the K-5, and also with less AA filter with the IIs. Otherwise the K-5 is an excellent camera.

Why K5-II not K5-IIs?. Answer is the removal of the AA filter, removing the AA filter is a good way of making pictures sharper and crispier but also there's consequences to it also, Moire' and False Color are the common problems people encounter when using sensors without AA filter. AA filters are there for a reason as soon as they start producing digital cameras manufacturers know about the problems encountered with sensors without AA filter.

Yes, you can fix this problems with softwares but you have to ask yourself do you really have to spend time in fixing your shots(and If you don't have the know-how) when this problems occur, I do some post proccessing as well cause I shot with RAW pictures only but I make sure that I get the results I wanted the time I shot the pictures so all I have to do is convert it to JPEGS. If time is spent tuning up your K-5 and K-5II you will definitely appreciate the picture quality it produce, and also good lenses are used.

K-5II/s is definitely better in lowlight Autofocusing (big improvement). Will look at getting a camera without AA filter in the future as soon as they fix all the bugs and introduce a better processor.

[bossa]

Just reading through this thread I get the feeling that many people are 'blurring the lines' a little (sorry about the pun) between the resolving power of an optical system and so-called 'sharpness' in photography. A K-5IIs, with the best lens available, likely has a higher resolving power than a D800E due to pixel density but when we talk about the resolution of a photograph it is a relative assessment because of standardized output formats, sensor size, resolving power of the system and accutance. Sensor size must play a big part in all of this when all other things are the same. When everything actually is the same, but for removing the AA filter that is deliberately placed over the sensor to mash up the pixels a bit (K-5II & K-5IIs), the result must be higher actual resolution (and not just accutance) as the recorded information is 'clearly' different in each camera - you can only add back accutance.. not actual resolution.

From another forum:

"This was Geoffrey Crawley's summing up of the terms in his precis of his longer article on Film developers published in 1960/1 "Notes on Present-day Monochrome Emulsions and their Development".

" Sharpness " - the overall impression of a print or projected image, measured scientifically as "acutance ", seen from normal viewing distance.
" Definition " - the extent to which fine detail is recognisably rendered in a print, etc. When acutance of fine detail is good, then definition is good.
" Acutance " - the contrast at the edge of significant detail, a scientific measurement of the density gradient at that point.
" Resolving Power " - the scientific measurement of the actual fineness of detail recordable by a lens, film, or developer, or any combination of these three.

Ian"

http://www.apug.org/forums/forum45/105950-sharpness-resolution-accutance-my-lack-clarity.html

An article on USM (Unsharp Masking):
http://www.prime-junta.net/pont/Photography_lessons/ppc_Lesson_2/_Sharpening.html