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Forum: Pentax K-30 & K-50 07-16-2013, 07:41 PM  
K-50 video quality
Posted By Sean Nelson
Replies: 8
Views: 7,402
I have a K100DS and several classic and newer DA Pentax lenses. I've been waiting for a good 1080p60-capable hybrid camera, hoping that Pentax might deliver, and have been disappointed time and time again over the past couple of years. I'm tired of waiting. It's looking more and more like I'm going to have to abandon my Pentax system as there are now plenty of very good alternatives available...
Forum: Video and Pentax HDSLRs 09-20-2010, 08:36 PM  
The 180 Degree Shutter
Posted By Sean Nelson
Replies: 22
Views: 9,102
It's not about the shutter, it's about the exposure. If you want your DSLR to produce movies that have the same look as movies shot by a film camera did, then you need to make sure that each frame of the movie has an exposure that lasts for about 1/2 of the interval between frames. So if you're shooting at 30 frames a second you need to use a shutter speed of 1/60th of a second. Doesn't matter (for the most part) if you use an electronic shutter, focal plane shutter or leaf shutter as long as it's 1/60th of a second.

It's called a 180 degree shutter because that's what the cinematographers used to call it. Kind of like how everyone using digital cameras tends to quote a lens' field of view as if it was equivalent to some other lens on a full-frame 35mm camera.
Forum: Pentax SLR Lens Discussion 10-07-2009, 12:11 AM  
Old style asahi pentax lens cap - question
Posted By Sean Nelson
Replies: 12
Views: 3,879
Pentax also made spring-loaded caps with two tabs that grip onto the filter threads. I have several of them for a 49mm thread which came with the 28, 50 and 100mm lenses I bought back in the 70s and 80s.
Forum: Pentax DSLR Discussion 10-07-2009, 12:06 AM  
White camera owners
Posted By Sean Nelson
Replies: 18
Views: 3,203
Someone might think you guys are white supremests for using a color additive system in which black (#000000) is less than white (#FFFFFF)... :D
Forum: Troubleshooting and Beginner Help 10-06-2009, 11:50 PM  
minimum focussing distance of Macro lens
Posted By Sean Nelson
Replies: 6
Views: 6,147
Focusing distances are normally measured from the "film plane" (ie, from the sensor in a digital camera). When you get into macro distances this becomes a lot less useful, so magnification ratios (1X, 1.5X, etc.) are used instead, where the ratio is between the actual subject size and the size as rendered on the sensor.
Forum: Pentax SLR Lens Discussion 07-30-2009, 06:28 PM  
f-stops....what do they stand for???
Posted By Sean Nelson
Replies: 8
Views: 2,193
If you remove a zoom lens from your camera and look through the front of it while holding it up against a white background and rotating the zoom ring, you'll see that the apparent diameter of the white circle decreases as you zoom toward a wider angle of view. This is the "effective aperture", and it's what's used in the f/ratio calculation.
Forum: Pentax SLR Lens Discussion 06-25-2009, 11:06 PM  
Wide dilemma
Posted By Sean Nelson
Replies: 21
Views: 2,706
Guard that cap with your life! It slips off as easily as it slips on, and I lost mine many, many years ago. If you loose it, you'll find that it's basically impossible to replace.
Forum: General Talk 06-25-2009, 11:01 PM  
Oly... answer - micro 4/3
Posted By Sean Nelson
Replies: 343
Views: 39,338
:) :) :)

You sir, are clearly no Kwyjibo.
Forum: General Talk 06-25-2009, 12:00 AM  
Oly... answer - micro 4/3
Posted By Sean Nelson
Replies: 343
Views: 39,338
Hey, I'm over 50, shot slides for many years, and have a perfectly crumulent PC which I'm about to replace with a Core i7. (And in fact I DID go through all my slides and negatives and scanned them in.) Give ME a break! :D
Forum: General Talk 06-24-2009, 11:56 PM  
Oly... answer - micro 4/3
Posted By Sean Nelson
Replies: 343
Views: 39,338
Actually, I typoed my statement, what I meant was SLIDES are to NEGATIVES as JPG is to RAW.

What I'm getting at here is that when you shoot slides, there's no "post-processing". You get whatever you get, and there's no opportunity for exposure correction, contrast adjustment, etc. etc. With negatives, you have a lot of latitude for adjustments when you make the print.

Similarly, with JPG you've got less leeway to fiddle with the image than you do with RAW.

So if your father is used to slides and the attendant requirement to get the exposure and framing etc. right with no opportunity for rescuing the image later, then JPGs might be right up his alley.
Forum: Pentax News and Rumors 06-19-2009, 09:17 PM  
"Battery Safety Firmware" - will others follow?
Posted By Sean Nelson
Replies: 21
Views: 4,092
I bought a supposedly "genuine" replacement battery for my 2000-vintage Nokia cell phone. When it was installed IN THE PHONE and the phone was turned on (but not in an active call) the battery got so hot I couldn't hold the phone. That was a BATTERY problem, not a USER problem. There was no way I was going to continue using that battery.

Since I had no other source of batteries, it was at that point I concluded that I needed to buy a new cell phone JUST so I'd be able to buy new batteries. There was absolutely nothing wrong with the phone, but because it used proprietary batteries and because Nokia wasn't interested in sourcing reliable batteries for them any more, it had become obsolete.

Proprietary batteries - BAH!
Forum: General Talk 06-19-2009, 09:10 PM  
Oly... answer - micro 4/3
Posted By Sean Nelson
Replies: 343
Views: 39,338
You understand that the relationship of SLIDES:FILM is the same as JPG:RAW, right? So he's just continuing his modus operandi. (And I say this as a slide shooter from way back.)
Forum: Troubleshooting and Beginner Help 06-18-2009, 10:38 PM  
Warmer Sunrises and Sunsets
Posted By Sean Nelson
Replies: 19
Views: 3,451
Not only is it not safe for your eyes, but if you have the wrong lens on there (a fast telephoto, for example) you're apt to melt the plastic viewscreen...
Forum: Photographic Technique 06-18-2009, 12:02 AM  
white background
Posted By Sean Nelson
Replies: 8
Views: 2,572
It depends on the relative illumination of the sky vs. the subject. If the sun is behind you and hitting the subject, and if the sky in frame is really sky and not clouds, then getting a shot with blue sky wouldn't be that challenging. But in different lighting conditions it can be impossible.

In addition to the flash suggestions, if you really have blue sky in frame and if the portion visible in the frame is at the correct angle from the sun, then a polarizing filter can darken the sky by as much as a stop, which can also help balance it's relative brightness vs. the subject.
Forum: Pentax SLR Lens Discussion 06-11-2009, 10:54 PM  
Wide dilemma
Posted By Sean Nelson
Replies: 21
Views: 2,706
I don't have the DA15, but I do have the K15/3.5. It's very nice and has an absolutely amazing field of view on my film cameras, but the crop factor really takes a toll. I really don't use it any more now that I have the DA12-24.

You should be aware that it's a LOT bigger and heavier than the DA15. In fact it's comparable to the DA12-24 in size and weight:

Forum: Pentax SLR Lens Discussion 06-07-2009, 12:27 PM  
Ultra Wide Angle Primes, DA15mm best choice?
Posted By Sean Nelson
Replies: 16
Views: 4,904
Nyaa nyaa, you can't have both!

Given your kit of primes I'd think that the DA15 would be a natural fit - its compact and shares filters with the others. The DA14 is going to be a bit of a chore to bring along and you'll probably neeed a new set of filters for it. My experience with the DA12-24 is that it's pretty each to grab indoor shots at F/4 because the SR is so effective at these wide focal lengths.
Forum: Pentax SLR Lens Discussion 06-07-2009, 12:19 PM  
wide angle dilema
Posted By Sean Nelson
Replies: 6
Views: 1,738
My opinion is that if you're comparing these lenses ONLY on the basis of their focal lengths then yes, there's no point in getting the 15mm if you know you'll be getting the 16-50. But there's a lot to distinguish the two lenses - the 15mm has a lot less distortion, is much smaller and lighter, and shares filters with the other limited lenses. If none of those things are important to you then it's probably not the right lens to buy.

Again, it depends on whether you get "hooked" on wide angle shots. If you do, then yes, you'd definitely miss the extra field of view.

I agree that the extra 2mm (assuming you're "kit" is the 18-55) seems a pretty meager benefit for buying a new lens. My solution was the DA12-24 (although I'd still like to get the DA15 if it's price comes down a little). It's a beautiful lens, but costly now that the price has gone up. I'm have no experience with the Sigma 10-20 but Photozone seems to think it's decent and from your musings I suspect it may be a good fit for you.
Forum: Pentax DSLR Discussion 06-07-2009, 12:06 PM  
Learning curve?
Posted By Sean Nelson
Replies: 12
Views: 2,165
I would think of the K7 as being a superset of the K100DS. Everything you're able to do on the K100 you'll also be able to do on the K7, and while a few buttons and menu items may be in different places, that's not really something that I'd consider a "learning curve".

The K7 can also do a lot MORE than the K100DS, but you can ease into that stuff as quickly or as slowly as you want. You not forced to use the features just because they're there - so I wouldn't be concerned that it's too much for you to handle.
Forum: Photographic Technique 06-07-2009, 11:57 AM  
Moon Shots and Elevation
Posted By Sean Nelson
Replies: 31
Views: 5,306
It really depends on what you're going for. If you want a shot of a pizza-pie moon hanging over a twilight landscape, then resolution of the moon itself isn't going to make that much difference to the shot and you're still shooting horizontally through dozens to hundreds of miles of atmosphere and so a mile or so of altitude probably won't make that much difference.

If you're going for a shot of the moon high in the sky and you just want the maximum possible magnification to reveal details of craters, etc., then altitude CAN buy you something - but the stability of the air is more important. Better to shoot from near sea level in very calm air than from 5000 feet when all the stars are twinkling like mad.

As far as city vs. country goes, country shooting is great for faint objects because there's no sky glow, but that's really not relvant for moon shots. But cities do tend to have less stable air which can be an issue as noted above.

"The next couple of weeks" will be from full moon, through last quarter and towards new moon (which is on the 22nd of June). If you're going for lunar details such as craters, you'll probably want to shoot within a few days of the 15th which will be last quarter. But the moon doesn't rise midnight at last quarter and it will rise later and later every day. Toward new moon you'll have to get up ahead of the sun to see it. A week or so after new moon it will be first quarter and another opportunity for nice crater shots without having to stay up until the wee hours of the morning.
Forum: Pentax SLR Lens Discussion 06-06-2009, 10:23 AM  
DA 55-300 - Problem or normal?
Posted By Sean Nelson
Replies: 27
Views: 5,892
The Photozone review states:
The Pentax lens exhibits negligible distortion at 55m. In the 100-300mm range you can expect a medium degree of pincushion distortion which may be visible at times in field conditions.
The amount of distortion in the brick wall photos posted here seems similar to that shown in the graphics on the Photozone site. I won't comment on the sharpness question, but it looks to me like for this lens there's nothing abnormal about the distortion people are seeing.
Forum: Photographic Technique 06-05-2009, 03:18 PM  
What's your backup strategy?
Posted By Sean Nelson
Replies: 133
Views: 18,441
Very nice, except that RAID is NOT backup (as per several previous posts in this thread)...
Forum: Lens Clubs 06-04-2009, 11:29 AM  
The M Club!
Posted By Sean Nelson
Replies: 6,361
Views: 917,321
I find the backgrounds in the full frame shots to be distracting, but I really like that last crop!
Forum: Pentax DSLR Discussion 06-04-2009, 11:27 AM  
focus point... is yours in the centre?
Posted By Sean Nelson
Replies: 13
Views: 2,848
I understand what you're saying. But I've learned that on Internet forums great huge all-out wars can erupt over different interpretations of a words' meaning - so I try to take care to choose the right ones... :D
Forum: Pentax DSLR Discussion 06-03-2009, 11:42 PM  
focus point... is yours in the centre?
Posted By Sean Nelson
Replies: 13
Views: 2,848
I've only measured my centre AF point and so I can't comment on the relative area covered by the other points.

But I don't think it's right to say that an AF point that covers a smaller area is "more accurate". In my book "accuracy" of an AF point means it can bring an object within it's field of view to sharp focus. That's a different than saying it has a small field of view.

There seems to be a feeling among some of the posts I've seen that an AF point that covers a large field of view is a bad thing. I don't agree. If the AF point is very small then it's more difficult to make sure the subject you want to focus on is within that point's field of view. Making the field of view smaller is a tradeoff.

Since we don't have adjustable AF field of view (yet, anyway), we just have to understand how the camera works and use it accordingly, IMHO.
Forum: Pentax SLR Lens Discussion 06-03-2009, 11:34 PM  
Help finding a extention tube brand I can order in Canada
Posted By Sean Nelson
Replies: 8
Views: 2,171
Hmmm... I did a quick search at the Canadian web sites that I have a note of and nary a trace of extension tubes. I think you may be stuck with waiting for a Craigslist or eBay listing...
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