Forgot Password
Pentax Camera Forums Home
 
Log in or register to remove ads.

Showing results 1 to 14 of 14 Search:
Forum: Pentax SLR Lens Discussion 04-06-2019, 10:04 AM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Found It !

Takumar 200mm f4


As you said, on the Takumar, it's a matter of playing with the focusing barrel on the above picture.

1. Unscrew the three screws
2. Move the barrel back
3. Rescrew
4. Repeat as needed

Tair 3S


For the Tair 3S, it's even simplier. As said on the Tair-3 (300/4.5 part of the photosniper) repair guide , the front part of the lens (the one with "Made in Russia" on my lens) is the "infinity lock".
1. Unscrew the three screws
2. Move the infinity lock to your need (unscrew it to move the front lens closer from your sensor)
3. Recrews the three screws

An important note though : DO NOT put too much force on the screws. I broke one of the screw head by tightening it :( I'm not sure I'll be able to ever remove it again...
Forum: Pentax SLR Lens Discussion 04-04-2019, 12:04 PM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Sadly I cannot try the first method at the moment. I'm traveling around and do not have a place to operate on the lenses safely.
I'll try the second one as soon as possible and keep the thread updated. It definitely makes sense, especially when you consider the fact that at infinity, there is a weird gap between the front and rear part of the lens. Could it be the offset that I miss to achieve focus to infinity ? Who knows :D

Just to be absolutely clear, the "grub screws on the outside of the focus ring" you're talking about (or this thread for that matter), are they the ones you can see on this picture or the ones just above the aperture ring ?
Forum: Pentax SLR Lens Discussion 03-30-2019, 06:17 AM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Here is the updated guide with pictures hosted on the forum itself.

Super Takumar 200 f4 repair guide
Forum: Pentax SLR Lens Discussion 03-30-2019, 04:06 AM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Well, thank you all again for your advices. I'll try to go with the adjustement/repair way and see how it turns out. I'll try to keep this thread updated when I do so, might be useful to others as well one day :)
Forum: Pentax SLR Lens Discussion 03-29-2019, 08:51 AM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Oh nice thread ! I found the same one a few hours ago, but none of the images would load so I set it aside. I'll have a deep look at it again and see if I can do something about that issue.

For information, I look inside the lens and at infinity, there is still space left inside for the front group to come forward. At least there is some hope :)

---------- Post added 03-29-19 at 09:14 AM ----------

And that one for the Super Takumar seems pretty good too.
All the image are gone but it is just their urls which are malformed, pretty easy to modify to get the full document.

I'll try to fix the whole thing and repost it somewhere.

Asahi Super Takumar 200mm f4 repair guide
Forum: Pentax SLR Lens Discussion 03-29-2019, 02:21 AM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
I see. Sadly, I don't know where to find such lens at the moment. And I doubt a shop selling one would let me bring the lens home at night to try it in such conditions :(




That could explain the focus offset that is pretty identical between the two lenses.





Do you have any ressources to recommended on how to do it ? I know nothing about lens internal construction and don't want to end up on the wrong tutorial :lol:
I'll look for a technician, but from what I can tell, those are pretty rare nowadays. I went by a photo shop yesterday, and the guy told me that he knew "no one that can do this sort of work"...

Thank you all for your replies, gives me hope that I might a solution in the end :)
Forum: Pentax SLR Lens Discussion 03-28-2019, 04:03 PM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
I had a similar response on CloudyNights. I don't understand how this could be true when there is no gap left for the lens to move backwards.

I mean if that was indeed the problem, some gap would be visible when focusing at infinity right ?

Also, both lenses seems to have the same offset, which is unlikely if they had been worked on. Don't you think ? :)
Forum: Pentax SLR Lens Discussion 03-28-2019, 03:39 PM  
Trouble focusing to infinity with M42 lenses and Pentax adapter
Posted By blemasle
Replies: 19
Views: 3,587
Hi,

I'm trying to use two old M42 lenses (Super Takumar 200mm f4 and Tair 3S 300m f4.5) on my K5-II for astrophotography and hence need precise focus to infinity.
The problem is, even with the official adapter (no flange, sits fully within the body), I cannot get focus to infinity. Not by far, but enough to loose details on the result shots... :(

I cannot "go any further" on both lenses, and they present roughly the same offset (see the bathinov masks pictures), which let me think that the problem does not come from the lenses.
What could be wrong here ? Does anyone has ever faced such issues with official adapters ?
Forum: Digital Processing, Software, and Printing 12-11-2018, 04:07 PM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
Maybe just a confusion between -d and -D ?
I'll try to reach the maintainers of the Gihub repo.

We still miss an explanation of why the data is different depending on mode or ISO though.

I'll try to update this thread if anything comes up with DSS maintainers :)

Thanks again !
Forum: Digital Processing, Software, and Printing 12-11-2018, 02:08 AM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
Thanks a lot for the time you're investing into this !



The default settings of DSS is -4 (not -6) which according to the help is equivalent to "-6 -W -g 1 1". The important part seems to be the "-W". Without it, I can indeed get redish tint on all my images. With it (like DSS), I reproduce my issue on the file with a Black Point set to anything else than 0.



The Black Point EXIF seems to be used by dcraw :






Code:

>dcraw -v -j -t 0 -4 -d -T IMGP9837.DNG



Loading Pentax K-5 II image from IMGP9837.DNG ...

Scaling with darkness 513



And when "-k 0" is applied it gets discarded, which result in a redish image :





Code:

>dcraw -v -j -t 0 -4 -d -T IMGP9837.DNG



Loading Pentax K-5 II image from IMGP9837.DNG ...

Scaling with darkness 0



Finally, If I edit the EXIF Black Point/Level to 0 0 0 0, both command lines results in a redish tint. Setting the black point to its original value using "-k 513" produce a black image.





Code:

exiftool "-BlackPoint=0 0 0 0" "-BlackLevel=0 0 0 0" "IMGP9837 - Copy.DNG"



So the EXIF tag is vital for dcraw to load the image correctly.

From all that, I should indeed uncheck "Set black point to 0" at all times :)
I'm puzzled why the camera does change those EXIF and apparently the image data itself (if I'm getting this right) depending on the mode or ISO setting though ? Am I missing something from your explanation ? :p
Forum: Digital Processing, Software, and Printing 12-11-2018, 12:35 AM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
From what I can tell from the source code, DSS is using the following command to load my DNG files.






Code:

dcraw.exe  -j -k 0 -t 0 -4 -T {file}



The "-T" flag is just to output tiff files.
The "-k 0" set the black point to 0. If set on "faulty" files, I do get a redish tiff as an output.
Forum: Digital Processing, Software, and Printing 12-11-2018, 12:14 AM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
Sorry, I forgot about that part. I do not have the flags used by DeepSkyStacker to load the raws. I'll try to look if I can find something about that, as I just found out that DSS is now open source and hosted on github.
Forum: Digital Processing, Software, and Printing 12-11-2018, 12:01 AM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
Thanks for helping me out !
All those options were disabled when those DNG were shot. But Pentax (or at least my K5-II) is known for having some forced noise reduction for ISO 1600 and up, right ?

I'm using exiftool.
Below are the extracted relevant value for each file in the zip. The files with 0 Black Point/Level are the one that seems to work correctly with DeepSkyStacker.






Code:

======== IMGP9834.DNG

Black Point : 67 67 67 67

Black Level : 67 67 67 67

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 100

======== IMGP9835.DNG

Black Point : 129 129 130 129

Black Level : 129 129 130 129

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 200

======== IMGP9836.DNG

Black Point : 257 257 258 258

Black Level : 257 257 258 258

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 400

======== IMGP9837.DNG

Black Point : 513 513 515 515

Black Level : 513 513 515 515

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 800

======== IMGP9838.DNG

Black Point : 0 0 0 0

Black Level : 0 0 0 0

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 1600

======== IMGP9839.DNG

Black Point : 0 0 0 0

Black Level : 0 0 0 0

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1/8000

ISO : 3200

======== IMGP9922.DNG

Black Point : 511 511 513 512

Black Level : 511 511 513 512

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 2

ISO : 800

======== IMGP9924.DNG

Black Point : 0 0 0 0

Black Level : 0 0 0 0

Picture Mode : Bulb, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1.9

ISO : 800

======== IMGP9926.DNG

Black Point : 0 0 0 0

Black Level : 0 0 0 0

Picture Mode : Manual, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 2

ISO : 1600

======== IMGP9927.DNG

Black Point : 0 0 0 0

Black Level : 0 0 0 0

Picture Mode : Bulb, Off-Auto-Aperture; 1/3 EV steps

Exposure Time : 1.9

ISO : 1600



Let me know if I can be of any further help ! :)
Forum: Digital Processing, Software, and Printing 12-10-2018, 10:40 PM  
Black Level and Black Point issue
Posted By blemasle
Replies: 11
Views: 1,448
Hello all :)

I'm having trouble with DeepSkyStacker, which use DCRaw to load raw files. Some files appear "redish".

Attachment 433662
Attachment 433663

The issue relies with the black point (full story here), and I found that my Pentax K5-II set EXIF "Black Point" and "Black Level" tags differently depending on the mode and ISO level :

When in Bulb mode, regardless of ISO :





Code:

Black Point                     : 0 0 0 0

Black Level : 0 0 0 0



When not in Bulb mode, ISO =< 800, something like :





Code:

Black Point                     : 513 513 515 515

Black Level : 513 513 515 515



When not in Bulb mode, ISO > 800 :





Code:

Black Point                     : 0 0 0 0

Black Level : 0 0 0 0



Does anyone have the slightest idea what's happening here ? Is this a camera firmware bug ?
Some test DNG can be downloaded here.

Thanks !
Search took 0.00 seconds | Showing results 1 to 14 of 14

 
Forum Jump


All times are GMT -7. The time now is 09:47 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top