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Help please with IR


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#1 tollie

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Posted 19 December 2008 - 13:14

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I need some help.

I made a panorama in IR yesterday using my 90mm Summarit. I was using a BW 093 IR filter. I worked with focus and aperture but could not get a really sharp image. ISO was 160 and shutter speed was 0.7sec. I had the camera mounted on a tripod and used a shutter release. I think it was possible that part of the problem was that the trees were moving... but the buildings, I think, should have been sharper. They are interesting images in there own right but not quite what I wanted.

First is the full three exposure stitched image.

Attached File  IR_Panorama1-2.jpg   51.55KB   818 downloads

Here is a 100% crop of the buildings.

Attached File  IR_Panorama1.jpg   82.76KB   815 downloads

I have read the threads on the forum dealing with IR but if someone has some guidence I would welcome it.

Many thanks

#2 farnz

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Posted 19 December 2008 - 13:29

Todd,

Your problem is that IR focuses on a different plane from visible light.

The way I get past this shooting at infinity with most lenses is to put the infinity mark of the focus ring next to the f/5.6 mark on the dof scale. If you try this and adjust slightly to suit the lens(es) you're using you should find your pictures getting sharper.

Once you've learnt the 'offset' in focus you can judge closer objects and adjust the focus plus offset to suit. It's similar to using the red line that appears on older lenses for IR focus.

(Lovely example of a b&w IR shot btw.)

Pete.
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#3 SJP

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Posted 19 December 2008 - 13:35

The last time we discussed this it turned out that you can calculate the IR focus distance (roughly). This was based on analysing the IR focus indicator on a variety of 'old' lenses.

This gave rise to the IR focus guestimator in the spreadsheet (located under the DOF calculator).

Using the average IR focus correction factor (1.0039) and focussing the IR at infinite (100.000 meters is enough) I get that the visible focus should be set at 23.15 m. Hope this works. Succes!!
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#4 tollie

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Posted 19 December 2008 - 21:05

Farnz, Sjp,

Let me thank you for the assistance.

This morning I ran a series of tests on my 90mm Summarit and 50 pre-asph Lux... both take my BW 093 black filter. I ran the test systematically at standard apertures and at standard adjustments from infinity. Both lenses preformed best in IR at f5.6 and f8. Both required correction with the 90 needing a bit more than the 50. In general the 90 proved sharper than the 50 as one would expect with the older lens.

I then reran the panorama but this time did a bw conversion rather than manipulate the temperature.

Here are the two shots comparable to the ones I made yesterday:

First the full panorama

Attached File  Anasco Bay in IR.jpg   39.99KB   766 downloads

next the 100% crop

Attached File  Anasco Bay in IR-2.jpg   86.58KB   759 downloads

Last I was most impressed with the results I obtained closer in... same panorama just a bit more coverage than I had yesterday:

Attached File  Anasco Bay in IR-3.jpg   117.01KB   761 downloads

This was the result I was looking for.

So... again my thanks.

#5 jaapv

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Posted 19 December 2008 - 21:36

A useful rule of thumb is to use the 5.6 DOF mark as the pointer for scale focussing.
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#6 wparsonsgisnet

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Posted 19 December 2008 - 22:21

It's clear when focusing at infinity -- because there's only one way to move the lens -- but we're talking about the 5.6 point to the right of center focus, right?

This is equivalent to focusing closer, in the visible plane.

Does it help to shut the lens down, and should one stop by f8, or is there more room in the IR spectrum without encountering diffraction problems?
Bill Parsons (wparsons@gis.net), Boston, Leica user since 1970

#7 farnz

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Posted 19 December 2008 - 22:37

It's clear when focusing at infinity -- because there's only one way to move the lens -- but we're talking about the 5.6 point to the right of center focus, right?

This is equivalent to focusing closer, in the visible plane.

Does it help to shut the lens down, and should one stop by f8, or is there more room in the IR spectrum without encountering diffraction problems?

Bill,

Yes the 5.6 mark to the right of centre.

I personally find that stopping down increases the risk of IR 'hot spots' and I have a pet theory that it relates to the diameter of the aperture blades (the wider open the lens, less the hot spot shows). YMMV. :)

Pete.
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#8 SJP

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Posted 19 December 2008 - 22:44

The f/5.6 marking rule of thumb seems a bit further than the 23.15m I calculated. I know it is impossible to really set the focus to that distance with any accuracy. But my best guess, using the 90 TE barrel, would be that 23.15m is at f/11 (or to be more precise if you set infinite on the focussing ring to line up with the right f/11 marking on the barrel, then the lens is focussed at about 20-ish metres). So maybe the 'average' IR correction factor is no good for an average Leica lens, probably because they are much better designed than most glass out there.

I believe it was Jaap who mentioned that the APO lenses need very little IR focus compensation. But I'm sure someone will disagree:D
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#9 jaapv

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Posted 20 December 2008 - 01:25

It was indeed me. And yes, the amount of focus correction needed is dependent on the design of the lens, or more specifically, how far into the IR part of spectrum the chromatic correction extends. Leica APO lenses are quite good in that respect.
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#10 patackroyd

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Posted 20 December 2008 - 02:42

I have been watching this topic from the beginning and I do not pretend to understand all of the advice given. I am impressed however with the Photographs shown, I did not know it was possible to do infra red with digital. The longer I read this forum the more I am learning about photography and the M8, so today I ordered an infra red filter from my dealer as I would like to produce shots like the one's shown. I did understand about the focusing as I have used infra red film in the past with a Nikon with lens markings. I do not know however know how to set up the M8 menu for the best results, is it set to B&Wor do you convert in Photoshop. You will probably have guessed by now that I am not a digital expert. I have learned an awful lot about digital and what it can do in the very short time I have been in this forum, my only problem is can my bank balance keep up with the learning curve.

#11 jaapv

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Posted 20 December 2008 - 02:48

Very simple: Shoot DNG and convert for B&W in postprocessing. Don't do a simple desaturate in Photoshop, but use one of the many methods that have been advised on this forum. You do not have to set up your M8 in any special way and you can use normal metering.
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#12 ho_co

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Posted 20 December 2008 - 03:03

Todd--
Looks as if the experimentation worked! Very nice second example.


When LFI discussed doing "color infrared" with the M8, they suggested a quick way to find accurate focus for your lens: Shoot a picture, then enlarge it on the M8's screen to full 16x. Inspect (use a loupe if you want), then try again with closer focus. Test and compare till you get the best result.

Whatever offset you get with a given lens will be consistent with that lens at all distances, but obviously can't be generalized to other lenses.

In a quick test with the 28-35-50 Tri-Elmar, I found that I got best results at infinity by rotating the 10 ft (3 m) mark to where the infinity mark was. That is, if I was shooting a scene that the rangefinder said was at infinity, I reset the lens to 10 ft.

For other distances you rotate the lens the same amount. In other words, if the rangefinder gives you a distance of 10 ft, the quickest procedure is to notice where the infinity mark is now, and rotate the lens' 10 ft mark to that point.


Very nice work. I think you got it all figured out without us! :)

I know asking about panorama software can open a discussion, but just curious: What are you using?
Best,

Howard

#13 lars_bergquist

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Posted 20 December 2008 - 06:56

Even with best focus for IR, the result will never be as sharp as with visible light. This is a physical fact of life--even in the visible spectrum, an image in the blue part will basically be sharper than the red one! Also, as noted, lenses are corrected for the visible spectrum only, and that goes for apochromatic lenses too. So PP sharpening is in order.

By the way, my Zeiss ZM 18mm does have an infrared mark, and it works!

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#14 tollie

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Posted 20 December 2008 - 15:15

Hi Ho_Co,

The panorama was done with photoshop... very simple and it seemed to do a great job on auto.

My 50 pre-asph Lux required more of an offset (to the 5m mark), the 90 summarit needed an offset to the 1 of the 10m mark.

I have not tried it at distances other than infinity but if the offset is the same it should be easy... I think I will, untill it becomes more comfortable follow your advice... a bit of chimping.

#15 farnz

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Posted 20 December 2008 - 17:47

... I am impressed however with the Photographs shown, I did not know it was possible to do infra red with digital. The longer I read this forum the more I am learning about photography and the M8, so today I ordered an infra red filter from my dealer as I would like to produce shots like the one's shown.... .

Pat(?),

Most digital cameras have an IR-cut filter fitted to the sensor to eliminate colour imbalance caused by the IR but the M8 is well suited to IR work because it has a very weak IR cut filter and it's a rangefinder camera.

IR with dSLRs is more difficult (imho) because when the IR-pass filter is fitted to the lens you can't see anything through the viewfinder (unless you're using a R72 'deep red' filter when you may be able to see deep red outlines of your subject). This means that you have to compose, fit the filter, adjust the focus offset and shoot, which pretty much necessitates a tripod unless you're prepared to shoot 'blind'.

The M8 allows you to shoot normally although the shutter speed will be significantly slower of course, but hand-held IR is quite practical providing that you shoot wide open or near to it. There is a temptation to increase the ISO to compensate for the slow shutter speeds but the resulting noise appears to be significantly worse and unacceptable to me above ISO 320. YMMV.

Visible light occurs in the waveband between about 400 nm and 700 nm although some people can see slightly above 700 nm. There are a number of different types of IR-pass filters on the market ranging from the Hoya R72 deep red (= B+W 092 = Wratten 89B), which cuts wavelengths below 680 nanometers, the Tiffen 87 'black' (= Wratten 87), which cuts wavelengths below 720 nanometers, and the B+W 093 'deep black' (= Wratten 87C), which cuts wavelengths below 780 nanometers. I've also used a SinghRay I-Ray IR-pass filter, which seems to be slightly 'blacker' than the 093 (ie lengths below 850 nanometers at a guess) although SinghRay hasn't published the wavelength transmittance data afaik.

Pete.
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#16 jev

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Posted 20 December 2008 - 21:55

Ok here is my opinion
I have been shooting with IR a lot

There are 2 types of filters i generally use R72 and 093
I like R72 more, but it's personal preference

Lenses in order of preference
CV 35mm 1.4 SC - excellent standard focusing works great no hot spots
Avenon 21mm 2.8 - excellent standard focusing works great no hot spots
CV 15mm .45 - excellent but need to watch out for light sources and hot spots

Lieca 50mm 2.0, 90mm 2.8 are ok but I do not find them usable enough, I think focusing issues are much more complicated with anything above 35mm with IR. Obviously 135mm is out of question.


Focusing - I think on 35mm and wider standard focusing works just fine, usually i shoot between f8-11, rarely for portraits 5.6

Hand holding - although you can get usable shutter speed out of M8 with fast lenses, I would hand hold only for portraits. Shooting landscape I try to use the tripod or monopod.

Here are some samples with 100% crops

Close range
photo
Posted Image

100% crop Flickr Photo Download: L1016341_crop
Minimal Sharpening in LR, I usually use very little

Landscape
Posted Image

100% crops, same minimal sharpening
Flickr Photo Download: L1016822crop1
Flickr Photo Download: L1016822ctop2

This is example of just test photo, hand held in the car, while standing at traffic light
Posted Image
larger version is here Flickr Photo Download: Infrared test of M8

I hope it helps
I truly believe that wider lenses do better with IR

Jev

#17 christoph_d

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Posted 20 December 2008 - 22:19

Dear all,

About a year ago I posed the question of IR-focusing correction to Leica and got the following answer:

Apo-lenses are corrected also for infrared light, so they can be used without focusing correction. ( I tried this using Film and a Apo-Summicron 90 aspherical with a 715 filter at f2 or 2.8, and it worked fine. Whether the narrower tolerances of an M8 still allow for this I cannot answer.)

Modern Leica M lenses do not have an IR index as they can only be corrected for a specific Film / Filter combination at infinity.

Leica advises as an approximation that an elongation factor of 1/300 (1/200 to 1/400) of the focal length is necessary, but tests are advised to find the exact position. This is done by pointing the camera to an object at infity, but focusing at a distance that represents 300 focal length of the used lens. For a 50 mm lens, for example, this would be 15 m. The results can be examined afterwards and fine tuning can take place accordingly...

In my trials this advice worked fine, I did not hower fine tune, but closed the aperture to f5,6 or f8.

Hope this helps, kind regards and merry X-mas,

Christoph

#18 ho_co

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Posted 20 December 2008 - 23:09

I have not tried it at distances other than infinity but if the offset is the same it should be easy... I think I will, untill it becomes more comfortable follow your advice... a bit of chimping.

Todd--I think my (brilliantly logical but uninformed) suggestion may be worth trying, but has been refuted here:

...
Modern Leica M lenses do not have an IR index as they can only be corrected for a specific Film / Filter combination at infinity.

Leica advises as an approximation that an elongation factor of 1/300 (1/200 to 1/400) of the focal length is necessary, but tests are advised to find the exact position. This is done by pointing the camera to an object at infity, but focusing at a distance that represents 300 focal length of the used lens. For a 50 mm lens, for example, this would be 15 m. The results can be examined afterwards and fine tuning can take place accordingly...



Christoph--Thanks for the information, and Merry Christmas to you as well!
Best,

Howard

#19 SJP

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Posted 20 December 2008 - 23:22

Modern Leica M lenses do not have an IR index as they can only be corrected for a specific Film / Filter combination at infinity.

Leica advises as an approximation that an elongation factor of 1/300 (1/200 to 1/400) of the focal length is necessary, but tests are advised to find the exact position. This is done by pointing the camera to an object at infity, but focusing at a distance that represents 300 focal length of the used lens. For a 50 mm lens, for example, this would be 15 m. The results can be examined afterwards and fine tuning can take place accordingly...

With the spreadsheet I got So+Si 12.87 for a 50mm at infinity in IR, not too bad as a first guestimate. Is there a document with Leica's advice online somewhere?
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#20 ho_co

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Posted 20 December 2008 - 23:26

... I am impressed however with the Photographs shown, I did not know it was possible to do infra red with digital.

Pat (?)--
Just to add one point to Pete's note above:

The M8 requires the UV/IR-cut filters simply because of its weak built-in IR filtration. The fact that other brands' cameras don't require the outboard IR filters is a tip-off of the fact that they filter the IR pretty well internally.

For that reason, there are companies who will modify Canons and Nikons for infrared use by removing their IR filters. (Then, of course, the cameras are usable only for infrared use.) But that doesn't make it any easier to compose and focus through the visually black or very dark filter.

As Pete said, the M8 is an excellent choice for both IR and visible light partially because of its rangefinder design.

Just remember when you use the IR pass filter you've ordered, be sure to remove the IR cut filter we use for general photography with the M8. :)
Best,

Howard




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