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Forum: Pentax K-r 02-28-2012, 06:11 PM  
Problem with Vivitar DF-283-PEN Flash
Posted By Opahujo
Replies: 5
Views: 2,066
Thanks for the tip, but, I'm sorry to say, it didn't fix the problem on the Kr.
Forum: Pentax K-r 02-27-2012, 06:45 PM  
Problem with Vivitar DF-283-PEN Flash
Posted By Opahujo
Replies: 5
Views: 2,066
This is a follow up to my original post of 02-08-2012 08:09 PM.

The vendor has been exceptionally cooperative paid for the return of the original flash and promptly sent a replacement. Unfortunately, the replacement flash does the same thing, flashes continuously (like a strobe light). In the meantime since my original post, has anyone else experienced a problem with the Vivitar Df-283-PEN flash when used with a Pentax DSLR camera?
Forum: Pentax K-r 02-08-2012, 06:55 PM  
Problem with Vivitar DF-283-PEN Flash
Posted By Opahujo
Replies: 5
Views: 2,066
I'm having a problem getting a brand new Vivitar Df-283-PEN to work on my Kr. The flash supposedly works with many Pentax DSLRs including the Kr. I have tried just about everything I can think of (P, M, At, and Auto modes; a manual lens and an auto zoom lens, manual and auto flash modes), always with the same results: Once it starts flashing, the flash keeps on rapidly flashing until I switch it off! Can anyone help me? Please.
Forum: Pentax K-r 12-22-2011, 08:22 PM  
Kr vs. older flash units
Posted By Opahujo
Replies: 6
Views: 1,526
That answered my question completely. I'm going see what's available in AF280Ts. Thanks for your prompt and informative reply to my question.
Forum: Pentax K-r 12-22-2011, 06:36 PM  
Kr vs. older flash units
Posted By Opahujo
Replies: 6
Views: 1,526
According to the Kr Operating Manual, page 180, "Flashes with reverse polarity (center contact on the hot shoe is minus) cannot be used do to risk of damaging the camera and flash."

I have two older flash units (Vivitar models 252 and 2800) that would be OK because they both have positive voltage on the center contact. But they also each measure in excess of 180 volts on the center contacts. I suspect that the Kr uses a solid state switch and 180 volts surely would blow that circuit ( I wonder why the Operating Manual does not warn about this).

Although the electrical circuitry would be quite simple, the major challenge with a home brew-device would be machining the mechanical interface for the hot shoe from scratch (Unfortunately, I don't have a junker flash lying around that I could salvage the hot shoe from).

My question then is this: Although I could design and build a buffer using a low voltage relay and a battery, I wonder whether there is something like this available commercially? In other words, an attachment that isolates the high voltage of older flash units from what I presume is low voltage circuitry in the Kr.
Forum: Pentax K-r 11-29-2011, 06:03 PM  
Kr Macro Operating Mode
Posted By Opahujo
Replies: 7
Views: 2,093
While I appreciate every one's replies to my question, yours was the answer I was looking for. If I understand you correctly, this means that if I stick a Pentax macro lens (one with a chip) on the Kr and select the Macro mode, the camera's software will select the optimum settings for that lens.

Again, thanks all for your comments. You have a great forum here and it's one of the reasons I decided to go back to Pentax equipment.
Forum: Pentax K-r 11-27-2011, 07:06 PM  
Kr Macro Operating Mode
Posted By Opahujo
Replies: 7
Views: 2,093
The only reference in the Kr Operating Manual concerning the Macro Picture Mode says: "Lets you take vibrant pictures of flowers and other small subjects at short distances."

I am familiar how Macro and Super Macro works in cameras with non-interchangeable lenses. There is also usually a table that shows the ranges for Macro and Super Macro shooting distances. But what does the Kr's Macro Picture Mode actually do? Is it intended to work only with certain lenses?
Forum: Pentax K-r 11-13-2011, 10:20 AM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
Got it. Your boxcar example really helped. So, a 50mm lens at F100 in the 35mm world means a pin hole diameter of 0.5 mm - that's not an unreasonable dimension.

Received my K-r yesterday. Although it comes with a 350 -page manual, it is the easiest to operate digital camera that I have ever used. The menus are fantastic and intuitive for the user. My hat's are off to Pentax. :D I took a shot in the HDR mode of a blackboard with a lunch menu that was next to a window - unbelievable great result compared to an Auto shot! In the latter mode, the whole shot was very dark and no writing on the blackboard was visible.
Forum: Pentax K-r 11-11-2011, 09:52 AM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
I'm still curious and for my own edification, the cannon S3IS tends to default to 6mm (as was pointed out to me in a post above) and when then in Av mode set to f8, is the aperture really0.75mm? Or is it electronically manipulated. From film camera experience I seem to recall that 0.75mm is getting into pin hole lens territory.

About your 18-55mm kit lens comments, I'm anxious to give it a workout. My K-r is scheduled to arrive today (UPS, unlike the USPS, delivers today).

I appreciate all the help that you provided. BTW: How do I become more than a "New Member?"
Forum: Pentax K-r 11-10-2011, 05:57 PM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
They are M lenses and one is a 28mm lens. I'm thinking that lens is close to a "Standard" lens (28mm x1.5=42mm). Although it's a manual lens, I like the idea that it has a DoF scale. Please comment.
Forum: Pentax K-r 11-09-2011, 09:36 AM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
I hope it's OK to re-post my question. I have spent many hours reading about DOF, FOV, APS-C, crop factor, etc., and I am beginning to understand most of the differences between film and digital photography, but I still don't know the answer to the above question. Can someone help, please.

My K-r is on order! :-)))
Forum: Pentax K-r 11-07-2011, 04:02 PM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
hnickesh, thanks for the suggestion. I have stitch software in my PC, but have not used it so far. Anyway, it doesn't look like there is a DOF problem - all the shots aren't as good as I think they should be, but it's not a matter that either near or far areas are clearly out of focus. I have played with about everything (lighting, exposure time and f stops, tripod of course, max. mega pixel,...) I could think of.
Forum: Pentax K-r 11-07-2011, 11:49 AM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
RioRico, first, thanks again for your patient explanation. It all seems so very logical, that is until I think about film cameras. I suspect digital cameras and how they work would be a lot easier for me to understand if I had never used a film camera. Sort of like my grandkids feeling much more comfortable with all the electronic gadges that are available these days than I am.

I also took your advice and ordered a K-r last night with the kit lens. I also orderd the rather expensive D-BH109 AA battery holder; but I like AA batteries and had good experience with the Copper Top ones. I buy 'em in quantity when they are 50cents a piece, and after their life in a camera I use them in PC mice.
Yep, I checked and most of my photos were indeed taken at the 6mm focal length and also mostly at F/2.7 to F/4 and f/8 in the Av Mode. F/8 at a focal length of 6mm would indicate to me that the aperture has diameter of 0.75mm. That's pin-hole lens territory! I have seen some great work done with a home-made pin-hole disk, but here again is where my thinking about my experience with film cameras gets me in trouble, because 0.75mm aperture diameter sounds wrong to me. By the way, I once had a set of three lens extenders that I used with the P30T and a 50mm lens to get in tight and I got some great close-up shots.

About the S3IS, I looked at the shots of my 8'x14' train layout again and you're right, DoF is not the problem - the focus seems to be uniform - but the details suck, like the writing on the sides of the cars just isn't "crisp." The strange thing is that pictures of a group of people, close-ups for stuff I sell sometimes on e-Bay, or most other uses are fine.
Forum: Pentax K-r 11-06-2011, 09:40 AM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
Please correct me if I'm wrong, but the way I understand it now, is that f8 on a P&S is the equivalent of a much higher f number on, say, the 35mm negative of a film camera.

I hope you'll bear with me, because I'm sure that I'll have more questions as I think about this. I turned 80 last May and I have been taking pictures and even developing my own B&W film since back in the early 1950s. But then there was a long hiatus for a carrier and raising a family. After that I bought a Pentax P30T, 35-80mm and 50mmm lenses, an extension tube set for close-ups, hot shoe multi-flash adapter, and more. Sold it all on e-bay for $80.99 net because I'd go all digital. :-(( I'm still kicking my butt about that.

Back on topic: Regarding the 18-55mm kit lense. I don't recall ever using the optical zoom on the Canon - I just don't need it. I either get closer or crop and enlarge on the PC. So, for the K-r I'm thinking about 50mm lens, either the M type I have or buying an A type. I'd appreciate your thoughts
Forum: Pentax K-r 11-05-2011, 04:52 PM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
RioRico, thanks for jumping in. First, I have the same DoF calculator bookmarked and I understand how that works. But I think I'm beginning to see my problem- I don't understand digital cameras. The lenses on digital cameras don't show an f-stop versus DoF scale. I know my S3IS only goes up to f8, but I think that's not quite the same as f8 for a film camera. Now, the spec for the 18-55mm kit lens for the K-r lists a Maximum aperture of F3.5-5.6 and a Minimum aperture of F22-38. I don't know why there are two numbers, but f22 or 38 should give me a much better DoF than I can get with the Cannon.
I should mention that I can throw a lot of light on the layout, use a tripod, and for hands-off-operation (if there is no provision for a remote shutter release) I can use the timer.

The bottom line is that if I'm going to spend $600+, I want to be sure that I'll see a considerable improvement over the Cannon S3IS.

Your comments would be greatly appreciated.
Forum: Pentax K-r 11-05-2011, 03:04 PM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
Adam, thanks for your quick reply. That's not good news. I have a K1000 and 28mm and 50mm M type lenses. I thought I'd get better DOF if I bought a Pentax K-r and used those lenses because my Canon S3IS is OK in general use, but does an absolutely lousy job when taking pictures of my train layout. I know there are situations where blurring is desired, but I'm looking for the exact opposite. Would a K-r with a kit lens do a better job for me than the Cannon?
Forum: Pentax K-r 11-05-2011, 12:25 PM  
Using M type lenses with the K-r?
Posted By Opahujo
Replies: 27
Views: 3,041
I have a large train layout and I need the depth of field that the f 22 and f32 apertures of the M lenses provide (used on my K-1000). I think the M lenses will mechanically mount OK on the Kr (I haven't ordered it yet). But will they work. I read somewhere that it requires the Av mode wide open, but another article said: "If older lenses without an "A" setting on the aperture ring are used in Av (Aperture Priority) Mode, an exposure error may occur." I would appreciate any comments, please.
Forum: Pentax SLR Lens Discussion 12-07-2009, 12:41 PM  
Online Depth Of Field Calculator
Posted By Opahujo
Replies: 20
Views: 16,019
I appreciate your reply. Thank you.
I have a Pentax SMC-M MACRO 1:4 50mm lens and a 1:2.8 28mm lens I bought on e-Bay in the mail to me. So, there is no problem with determining the focal lenght for those lenses. I also have a Canon S3IS with a 6-72mm 1:2.7-3.5 lens. The camera is listed in the table in the "Depth of Field Calculator." Is 75 the number I should use for that lens? (I hope it's OK to ask a question about a Canon camera in this Pentax forum.)
Forum: Photography Articles 12-07-2009, 12:41 PM  
Sticky: Online Depth Of Field Calculator
Posted By Opahujo
Replies: 27
Views: 36,956
I appreciate your reply. Thank you.
I have a Pentax SMC-M MACRO 1:4 50mm lens and a 1:2.8 28mm lens I bought on e-Bay in the mail to me. So, there is no problem with determining the focal lenght for those lenses. I also have a Canon S3IS with a 6-72mm 1:2.7-3.5 lens. The camera is listed in the table in the "Depth of Field Calculator." Is 75 the number I should use for that lens? (I hope it's OK to ask a question about a Canon camera in this Pentax forum.)
Forum: Photography Articles 12-06-2009, 10:12 AM  
Sticky: Online Depth Of Field Calculator
Posted By Opahujo
Replies: 27
Views: 36,956
About the "Depth of Field Calculator"; this is probably a dumb question but when using the calculator for a 15-55 kit lens, how do I figure out what number to use for the focal lenght?
Forum: Pentax SLR Lens Discussion 12-06-2009, 10:12 AM  
Online Depth Of Field Calculator
Posted By Opahujo
Replies: 20
Views: 16,019
About the "Depth of Field Calculator"; this is probably a dumb question but when using the calculator for a 15-55 kit lens, how do I figure out what number to use for the focal lenght?
Forum: Pentax SLR Lens Discussion 12-04-2009, 09:50 AM  
Field of view
Posted By Opahujo
Replies: 9
Views: 4,573
Interested Observer, thanks for the link to the "Dimensional Field of View Calculator." I do have a question about the "Online Depth of Field Calculator," which I bookmarked after finding it in another thread in this forum. I'm not sure whether I may ask the question in this thread, but here it goes: when you use the calculator for a 15-55 kit lens, how do figure out what number to use for the focal lenght?

If it's not Ok to ask that question in this thread, I'll be glad to post it in the Online Depth Of Field Calculator thread.
Thanks
Opahujo
Forum: Pentax SLR Lens Discussion 12-04-2009, 09:22 AM  
Field of view
Posted By Opahujo
Replies: 9
Views: 4,573
Quicksand, thanks for the information. I really appreciate it.

Yes, "B = 2 * A * tan ( FOV / 2 )" is exactly what I used, but instead of FOV/2 =32.5 I used 37.5. I didn't know that I needed to use the diagonal dimension.

Opahujo
Forum: Pentax SLR Lens Discussion 12-03-2009, 07:04 PM  
Field of view
Posted By Opahujo
Replies: 9
Views: 4,573
I sold my Pentax SLR film camera, lenses, extension tube set, and other accessories a few years ago when I went "digital". BIG MISTAKE! My Canon S3IS digital cameras works fine in most applications, but taking pictures of a large model train layout is not one of them. By being limited to f8, I can't get a decent depth of field.
So, recently I bought a 35mm Pentax K1000 with a Macro F 1:4 50mm wide-angle lens for $100 (I understand from reading various comments in the Pentax Lens Review Forum that this is an excellent lens that should render sharp images not just in macro. However, I'm somewhat limited how far I can get back from or above the train layout. I have been bidding on Pentax-M f2.8 28mm wide-angle lenses and finally got one that is in good condition for $55.99.

I read somewhere that the field of view for the Pentax-M f2.8 28mm wide-angle lens is 75. I don't remember where I saw it, but using 75 and a bit of trigonometry I calculated what the field of view "B" is at a distance "A"

A=4' B=6.13'; A=6' B=9.21'; A= 8' B=12.28'; A=10' B=15.53'

Is this correct or am I way out in left field? ;-)

I would appreciate your thoughts.
Thanks
Forum: Pentax SLR Lens Discussion 11-27-2009, 08:37 AM  
Question about Macro F1:4 50mm Lens
Posted By Opahujo
Replies: 5
Views: 3,234
jerrymouse wrote: My guess is 1:n (n being the number from 2 to 25) magnification.

That's it. Thanks for your reply. I checked and at numeral 2, a 70mm wide target approximately equals 35mm in width in the view finder, i.e., a magnification of 1/2.

Damn Brit wrote: Why are you limited to f/8?
That's the smallest aperture a Canon Power Shot S3IS has. This is not uncommon for even mid-priced digital cameras.
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