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Forum: Pentax DSLR Discussion 06-10-2016, 12:53 PM  
Petition - Please allow KAF4 firmware for the K3, K5 series, and K50
Posted By troyz
Replies: 227
Views: 20,031
Add my name to the petition.

If I have the opportunity to comment on the new 55-300mm F4.5-6.3 (in some manner that gets back to Pentax) I'll be sure to mention that it's unfortunate that I can't use it on my K-3.
Forum: Pentax SLR Lens Discussion 05-28-2012, 09:04 AM  
Samyang 8mm fisheye vs Sigma 10-20mm super-wide angle
Posted By troyz
Replies: 47
Views: 17,570
Hugin can do mosaic stitching with scale/yaw/pitch/roll correction

Hugin tutorial Stitching flat scanned images


(K20D, Pentax 12-24 @12mm, stitched from 4 exposures taken at different positions)
Forum: Pentax Medium Format 12-11-2010, 12:32 PM  
Medium Format Film Processing
Posted By troyz
Replies: 18
Views: 4,313
Here's what works for me (and is the opposite of what the previous posts describe).

Processing:
Everything goes to a local full-service film lab.

Film:
C41: Mostly Fuji 400H, sometimes Fuji 160C or Kodak Ektar 100. I'll probably switch to the new Portra 400 due to Fuji's recent habit of discontinuing films in a confusing manner.

Scanning:
Although I do all my own 135 scanning, I find scanning 120/220 film to be a real pain in the ass, so I have the lab do scans (8-bit TIFF) at time of development on their Noritsu scanner. If I need a 16-bit scan for extensive dodging/burning/contrast adjustment or a higher-res scan for a big print I get a rescan done on an Imacon.

BTW, since I mostly rely on scans at TOD, my cost per exposure is much cheaper for 220 film than for 120 film.
Forum: Pentax SLR Lens Discussion 12-09-2010, 11:05 PM  
UWA Advice
Posted By troyz
Replies: 9
Views: 1,758
Hey, I found one with the sun in it.

Kodak Ektar 100. The composition leaves much to be desired and from the not-so-saturated color it looks like I overexposed a bit :o



I see a few ghost spots on the sculpture and a ghost arc on the apartment building immediately to the left.
Forum: Pentax SLR Lens Discussion 12-09-2010, 10:27 PM  
UWA Advice
Posted By troyz
Replies: 9
Views: 1,758
IIRC I haven't had problems with veiling glare when the sun is in the image but I do get some ghosting. Sun stars are 10-pointed (due to the 5-bladed diaphragm).

I'm not sure that I have any images online to demonstrate this -- probably best just to look at the sample images on pbase (link in my previous post) and make your own judgment.

Of course, if you're using a digital camera and the sun is in the image and the atmosphere is hazy you do have to be careful to avoid partially blown-out skies -- this is an issue with any ultrawide lens.
Forum: Pentax SLR Lens Discussion 12-08-2010, 11:29 PM  
UWA Advice
Posted By troyz
Replies: 9
Views: 1,758
I know of two Sigma 8mm fisheyes made in Pentax mount. I have the 8mm/4.0 EX autofocus model (not the older manual-focus filtermatic). An 8mm/3.5 model was announced a few years ago but I don't think it was ever released in Pentax mount.

Metal exterior. Focus ring runs Canon-wise (the opposite of Pentax-wise) and has a bit of drag -- not as loose as most AF lenses, not quite as pleasant as an FA limited, but certainly not objectionable. No barrel wobble. The focus adjustment stop is beyond infinity (by design).

Lots of images (mostly not mine) at Sigma 8mm f/4.0 EX Circular Fish-Eye Lens Sample Photos and Specifications .

I think it's contrasty and colorful enough. I usually add a lateral chromatic aberration correction and some sharpening in Lightroom to clean up the edges of the image a bit.

(K20D, ISO 100, f/6.7, cropped)


(K20D, ISO 400, f/5.6, vignetting added in lightroom)
Forum: Pentax SLR Lens Discussion 12-07-2010, 11:16 PM  
Fisheye question
Posted By troyz
Replies: 15
Views: 4,849
. . . actually the term "full frame fisheye" is older and more common than "diagonal fisheye", although potentially confusing now that "full frame" commonly refers to sensor size.
Forum: Pentax SLR Lens Discussion 12-07-2010, 10:21 PM  
Fisheye question
Posted By troyz
Replies: 15
Views: 4,849
I think SpecialK meant to type "diagonal fisheye".



Depends on the lens and sensor/film size. An 8mm circular fisheye (such as the Sigma 8mm) shows a full circle on flim.


On APS-C digital, the top and bottom are cut off. It's pretty common to crop out the remaining black areas on the left and right (resulting in a diagonal fisheye image with a flexible aspect ratio).

RE metering with a circular fisheye:
It is usually sufficient to use center-weighted metering and substitute meter from a light gray object.
Forum: Film Processing, Scanning, and Darkroom 11-19-2010, 12:26 PM  
Blue Color Cast to my Color Negative Prints
Posted By troyz
Replies: 9
Views: 5,746
Quite likely.

Slowpoke: Try comparing your fuji 400H negatives with your "good" Kodak 400 negatives. It's normal for the orange mask to be slightly darker on the Fuji 400H (and other fuji pro films, and Reala) than Kodak stuff, but it it's radically different it's probably bad processing.

See JOBO AG for C-41 troubleshooting info.
Forum: Pentax SLR Lens Discussion 11-18-2010, 07:45 PM  
Why isn't this lens Auto Aperture?
Posted By troyz
Replies: 12
Views: 2,052
Actually, this might be a pure ricoh R-K mount (rather than a hybrid pentax/ricoh mount). I don't see a contact pattern to the right of the orange dot (in the photo in the first post).

If so, there's no way for the body to know the aperture range of this lens, and it was never possible to use this lens as a Pentax KA lens.
Forum: Pentax SLR Lens Discussion 11-09-2010, 11:48 PM  
? about odd 35-70 f2.8 AF from Pentax
Posted By troyz
Replies: 9
Views: 2,704
It's been done but is considered ugly and blasphemous. :eek:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/43371-unique-s...-70-2-8-a.html (Pictures gone but text contains enough gory details)
Forum: Pentax SLR Lens Discussion 10-20-2010, 12:19 PM  
Defocus (bokeh) control lens for Pentax
Posted By troyz
Replies: 10
Views: 3,274
Forum: Pentax SLR Lens Discussion 10-17-2010, 08:48 PM  
Split prism screen calibration
Posted By troyz
Replies: 16
Views: 4,176
Oh crap. You are right -- a longer lens (with all other terms held constant) is better.

Will edit previous posts.




According to https://www.pentaxforums.com/forums/907364-post4.html
they range from 0.15mm to 0.40mm in 0.05mm increments.
Forum: Pentax SLR Lens Discussion 10-17-2010, 04:54 PM  
Split prism screen calibration
Posted By troyz
Replies: 16
Views: 4,176
The depth-of-focus is how far the film/sensor/focus screen can be from the plane of focus and still get an acceptably focused image.

(EDIT: text deleted)
Forum: Pentax Medium Format 10-17-2010, 04:24 PM  
Help! Part # for 67 viewfinder ring/glass?
Posted By troyz
Replies: 6
Views: 3,471
Phone numbers for all Pentax subsidiaries are available at:

http://www.pentax.com/subsidiary.html

In the US, you need to talk to Pentax Imaging (Colorado), not Pentax Medical (New Jersey). Not sure whether the other subsidiary offices have parts.
Forum: Pentax SLR Lens Discussion 10-17-2010, 12:46 PM  
Split prism screen calibration
Posted By troyz
Replies: 16
Views: 4,176
For calibrating focus screens:

(1) If Katz does the shim adjustment you don't need to send a lens, just the body.

(2) To accurately test focus screen calibration, you need shallow depth-of-focus, rather than shallow depth-of-field (check wikipedia for definitions).
(EDIT: text deleted)
Forum: Lens Clubs 10-10-2010, 01:38 PM  
Fisheye Fever Club -- Flaunt your fisheye photos!
Posted By troyz
Replies: 2,994
Views: 511,827
Since the Zenitar came up recently in another thread:


Pentax MZ-S, Zenitar 16/2.8 Fisheye, Kodak 160NC
Forum: Pentax SLR Lens Discussion 10-10-2010, 01:35 PM  
How fishy is a Zenitar 16 mm F2.8? (next to Tamron 10-24 mm)
Posted By troyz
Replies: 36
Views: 17,366
Hmmm. . . I have a Sigma 8mm and a Zenitar 16mm and the Zenitar goes in my bag more often, usually as a diagonal fisheye for film, and/or a compact and cheap substitute for my Pentax 12-24 on digital in adverse conditions.

I agree with RR: a (non-zoom) diagonal fisheye is a specialized tool for messing around with geometry. :)



a 10mm rectilinear lens has a wider field of view on APS-C than an 16mm fisheye, so any shot you could do with a Zenitar on APS-C is feasible with your Tamron 10-24. It's pretty easy to introduce the Zenitar's fisheye distortion in postprocessing if you just want to make your ultrawide shots fishier.


The colored filters that mount to the back of the Zenitar are for black-and-white film. Use the clear one for color.
Forum: Pentax Film SLR Discussion 10-02-2010, 05:43 PM  
Where can i order hi speed BW film
Posted By troyz
Replies: 8
Views: 2,403
You should be able to get Neopan 1600 or Ilford Delta 3200 from Glazer's camera supply in Seattle. Call first, sometimes they have stuff in stock even when their web site indicates that they do not.

I'd suggest Panda Lab in Seattle for processing (if you don't want to start DIY processing right away).
Forum: Pentax Film SLR Discussion 09-03-2010, 04:52 PM  
ZX-5N flash repair
Posted By troyz
Replies: 9
Views: 3,159
More MZ/ZX-series flash repair info:
MZ cameras Photo Gallery by Alan Chan at pbase.com
Forum: Pentax Camera and Field Accessories 08-22-2010, 10:22 PM  
Katzeye sans Optibrite
Posted By troyz
Replies: 6
Views: 2,931
If you primarily use fast lenses, you probably DON'T want the optibrite treatment. Optibrite produces a brighter image, but at the cost of decreased focus accuracy (specifically, increased apparent depth of field) for the matte portion of the screen.

See ("Optibrite or not") at OptiBrite Brightness Enhancement - KatzEye Optics .

The split prisms/microprisms are much easier and faster to use than the focus confirm light/beep and the standard screen -- but only more accurate if your focus screen is properly calibrated. See various threads here about calibrating the focus screen shim.
Forum: Pentax Medium Format 08-19-2010, 01:59 PM  
Workflow for Scanning on Coolscan 9000
Posted By troyz
Replies: 3
Views: 3,784
Regarding scanner settings: this is what I settled on for the LS8000+Nikon Scan:

-- 16 bit, 2000dpi, unless doing a tight crop

-- ICE on, FINE mode (off for traditional black-and-white film, of course)

-- Super Fine scan mode (IIRC it's in the "scanner extras" section of the controls) -- results in much slower scans but eliminates vertical banding artifacts

-- Auto focus on, select focus point manually for each frame

-- DEE and ROC off (I've never run into a case where DEE and ROC did a better job of fixing colors than manual fiddling in photoshop)

-- GEM off (I've never had to worry about grain with medium format film :) )

-- Auto exposure on (but beware that for C41 films, auto exposure might shift the black point slightly)

With E6 you can import the TIFF directly into Lightroom; with C41 (especially the Fuji pro stuff) you might need to make at least one trip through Photoshop to remove color casts by setting the R, G, and B channel black points. Sadly, Lightroom doesn't let you set these individually.

Also, check carefully for Newton rings if you are using the glass film holder.
Forum: Pentax Medium Format 07-23-2010, 11:02 AM  
67II Frame Spacing Issue
Posted By troyz
Replies: 10
Views: 4,040
Is there a slip clutch for the takeup spool of a 67II?

I've seen the faulty-takeup-spool-clutch-causes-erratic-frame-spacing problem on the older 67, but my impression is that the film transport on the 67II works quite differently, using an electronic rotary encoder to measure film travel and some other electromechanical bits to stop the film transport once the film has traveled the distance of one frame.

At least this is what I recall from my discussions with the local repair guy.
Forum: Pentax Camera and Field Accessories 07-08-2010, 10:42 PM  
Washer (shim) for focusing screen - how to select?
Posted By troyz
Replies: 15
Views: 4,393
In principle you could try to measure the focus error, determine the thickness of the shim you have now (with a micrometer?), and calculate the thickness of the replacement shim. . .

but in practice I think the trial-and-error method will be faster.

A link to Wheatfield's thread with shim part numbers and thicknesses in case you don't already have it:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/88289-k7-screen-shims.html

(FWIW, I had Katz re-shim my K20D in their shop)
Forum: Pentax Camera and Field Accessories 07-08-2010, 09:02 AM  
Washer (shim) for focusing screen - how to select?
Posted By troyz
Replies: 15
Views: 4,393
from Depth of focus - Wikipedia, the free encyclopedia :

"Depth of focus, however, is a measurement of how much the film or sensor plane can be displaced while an object remains in acceptably sharp focus."

Denoting depth of focus by t:

t = 2 Nc v/f
t = 2 Nc (1+m)

where
N = f-number
c = circle of confusion
v = image depth
f = focal length
m = subject magnification

---

m increases when you use the bellows, so t (depth of focus) increases with the bellows, which is undesirable because you won't be able to detect a difference between flange-to-sensor distance and flange-to-focus screen less than t.
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