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Forum: Pentax DSLR Discussion 05-16-2011, 03:16 PM  
Pentax DSLR market share
Posted By labnut
Replies: 52
Views: 12,883
The psychoanalytical reaction is almost inevitable. Again and again it happens that this question is asked, on this and our sister forums, with varying degrees of angst and despair. Your question is the latest installment in a history of similar questions.

This raises the question, why? Why not just accept that we have bought into a niche product? You knew that, didn't you, when you made your purchase decision? Why do so many people display so much concern?

You gave one answer, that you are concerned about the longer term viability of your chosen brand. But a great number of niche products survive and prosper.

Having read this question so many times it began to occur to me that there was a deeper process taking place. And the explanation ties into the related phenomena of the fiercely tribal loyalty that so many camera owners display. So while you give a rational answer it doesn't explain the deeper, underlying process which seems to be at work here.
Forum: Pentax DSLR Discussion 05-16-2011, 04:07 AM  
Just taking pictures
Posted By labnut
Replies: 13
Views: 2,282
Ah, the origin of black and white photography :rolleyes:
Forum: Pentax DSLR Discussion 05-16-2011, 03:50 AM  
Pentax DSLR market share
Posted By labnut
Replies: 52
Views: 12,883
This is such an interesting phenomena. It seems we adopt 'badges' to display our identity and to proclaim our group membership. We want a worthwhile identity (we want to be someone of consequence) and we need to belong to a powerful group (we need the protection and comfort of the group). In this process we align our thinking and values to conform with the group (groupthink).

When someone adopts the 'badge' of a small but distinctive group he is declaring his distinctive nature, his individuality and strength. He is strong and sure enough to function outside the comfort of a large group. He refuses to be confined by groupthink.

So take comfort, you are no ordinary person.
Forum: Pentax DSLR Discussion 05-16-2011, 03:28 AM  
Just taking pictures
Posted By labnut
Replies: 13
Views: 2,282


No, I don't miss it it. It is just a case of adopting the right strategy for the moment. This is the debate of taking vs making a photo.

I like to use the analogy of the De Bono Six Thinking Hats approach(see the diagram below). In that approach you consciously don a certain kind of thinking hat. It means that you deliberately enter that thinking mode and bring that approach to the problem at hand. In the same way we, as photographers, put on different photographic hats at different times:
- The Journalist's Hat. We take a photo (the Red Hat)
- The Director's Hat. We make a photo (the Blue Hat)
- The Artist's Hat. We create a photo. (the Green Hat)
- The Critic's Hat. We assess the photo. (the Black Hat)
Taking a photo.
When he does this, the good photographer intuitively engages his store of experience as he 'takes' a photo. He need not consciously summons up that knowledge or plan the photo. It emerges without conscious volition. This is often desirable because creativity thrives without the limits placed on us by our conscious 'making' mind.
Making a photo.
Every photographer should be encouraged to engage in 'making' in the earlier stages of his photographic journey. By consciously engaging and practicing skills we embed them in deeper stores of knowledge so that they are quickly available to you, without thought, when you later engage in 'taking'. So we need to distinguish between the 'taking' of the unpractised amateur (snapshots) and the 'taking' of the experienced photographer. In the case of the experienced photographer these are not snapshots but are rather the fluency of practised skill. The diagram below outlines De Bono's Six Thinking Hats (copyright the De Bono Group). One is supposed to put on each hat in turn when approaching a given issue so that you approach it from all points of view.

Forum: Pentax DSLR Discussion 05-15-2011, 12:38 AM  
How so much people here don't admit with FF IQ advantage?
Posted By labnut
Replies: 249
Views: 23,250
That's because the APS-C format is ubiquitous, adequate and affordable. It's given us a useful, practical tool so that we can get on with the business of taking good photos. And that is precisely the point, right now we can get very good photos from the format. Because the lion's share of development effort has gone into the APS-C format.

In time the FF format will become ubiquitous and affordable and we will happily embrace the improvements that it brings.

Given your alias of 'Emacs' I presume you publish your photos under the GPL (v 3.0) and not the the Creative Commons licence.;) (I also admire Richard Stallman:))
Forum: Pentax DSLR Discussion 05-14-2011, 09:13 AM  
Measurement of lens flare (veiling glare) with and without UV filter
Posted By labnut
Replies: 4
Views: 4,999
The lenstip study is a good place to start looking for a high quality filter. My study did not try to answer that question, which filters are good.
Forum: Pentax DSLR Discussion 05-14-2011, 04:51 AM  
should pentax become more focused?
Posted By labnut
Replies: 19
Views: 3,394
I am looking around me at the walls where I display my large format panorama photos, taken with my K-7. And my reaction - Pentax does a pretty, darn good job.

I can think of a few improvements that I would like to see in my K-7 but the fact of the matter is that it is a fine tool for creative photography. I simply can't use my camera as an excuse for any shortcomings in my photography.

But what I really would like to see is Pentax do an improved version of the Fuji X100, a sort of affordable Leica with the Pentax name. (I can dream)

Forum: Pentax DSLR Discussion 05-14-2011, 04:30 AM  
Highight correction
Posted By labnut
Replies: 14
Views: 2,204
To understand the problem it helps to look at a dynamic range graph.
Below is the dynamic range graph that I measured on my K-7 from a series of RAW photos. (how I did this will be published in another post)
This is not the same as on your camera but the principle is the same.

One can see that the graph shows an extended toe. This means that the sensor can record fine gradations of near black.

But the opposite is true at the shoulder of the graph. Here there is an abrupt transition to saturated pixels. This means that the sensor cannot record fine gradations of nearly white. If you want to do that you must slightly underexpose the highlights so that they do not lie on the shoulder of the graph.

I presume this is what highlight correction does. There is no magic involved, the camera can't change the properties of the sensor, as seen on my graph.

When I need to preserve highlights accurately I prefer to spot meter on a chosen highlight and enter a corresponding exposure compensation, according to what brightness level you want to represent that highlight. The second illustration below shows the principle.




Forum: Pentax DSLR Discussion 05-14-2011, 12:39 AM  
Canon vs. Pentax which to buy
Posted By labnut
Replies: 18
Views: 5,891
To answer your second question first.
Right now I am looking at an A3 print taken on my old *istDS, an 6.3 Mpixel camera. The image is sharp and clear. So a 6 Mp camera can produce good A3 prints.

To answer your second question.
Image clarity is made up of two things, sharpness and contrast. They depend on, in order of importance:
  • a good lens

  • good photographer technique

  • good image post-processing technique

A good lens.
The most important thing in improving image clarity is to get a good quality lens. Here the rules are simple. The fewer the lens elements the better the contrast. The less zoom the better the sharpness. (but there are exceptions) And the best results (usually) come from a good quality prime lens. Browse through the lenses on slrgear.com.

Good photographer technique.
More often than not we are the cause of poor photos. This comes down camera shake and poor focusing. So it is worth re-thinking your camera technique. In the modern quickly, quickly, point and shoot age we have lost sight of the fact that good images require a lot of care.

Good image post-processing technique.

Post-processing can improve sharpness, contrast and colour. A great deal can be done at this stage to further improve your photos but I won't enumerate the techniques here.

You have done all the above things but are there still reasons to change your camera body?
Two important reasons come to mind.

  • Modern cameras/lenses have shake reduction. This greatly extends the range of your photography to low light conditions and smaller apertures for more depth of field.

  • Modern cameras can take good photos at high ISO, extending your photography even more into low light conditions. And when you discover this you wonder how you ever managed without it. It is that big a deal.

Forum: Pentax DSLR Discussion 05-13-2011, 02:10 PM  
Measurement of lens flare (veiling glare) with and without UV filter
Posted By labnut
Replies: 4
Views: 4,999
I started my study in reaction to seeing the Lenstip study. They carefully measured UV transmission which I felt was mostly irrelevant on today's digital cameras.

The really interesting issue, for me, was whether there was significant degradation of image quality as a result of using them.

But they did not measure this, they merely showed some comparative images taken under extreme conditions that did not represent normal use.

So I set about doing some careful measurements of veiling glare so that I could answer the question whether, under normal conditions, good UV filters degraded image quality.

Yes, my results apply to good filters. It seemed a complete waste of time to test bad filters since it is a given that bad filters will give bad results.

But that does not change the central finding, that good filters introduce an imperceptible loss of image quality.
Forum: Pentax DSLR Discussion 05-13-2011, 01:58 AM  
Shake reduction on tripod
Posted By labnut
Replies: 7
Views: 2,653
It doesn't hurt the camera, it simply makes your image slightly less sharp.
The reasons are as follows:

The camera contains three sensors that measure the rotation of the camera in the X, Y, and Z axes (role, pitch and yaw).

From the amount of rotation it uses a little bit of trigonometry to calculate how much to move the sensor in compensation.

But this calculation depends on knowing where the center of rotation is. If the camera is handheld that coincides with the axes of the camera. But when you mount it on a tripod or monopod the center of rotation is changed to an unknown point so the camera wrongly calculates the amount of compensation.

That said, because the amount of movement is small, the error is small.
Forum: Pentax DSLR Discussion 05-13-2011, 01:40 AM  
Measurement of lens flare (veiling glare) with and without UV filter
Posted By labnut
Replies: 4
Views: 4,999
Hi all,
Lens flare caused by UV filters has been a hotly debated topic for a long time.
Some people say UV filters are useful to protect the lens while others say you should avoid them because they degrade the image too much.

Curious to know the truth about the matter, I set out to carefully measure how much additional lens flare (veiling glare) is caused by adding a UV filter to a lens.

How the tests were done.
The tests were conducted by measuring the edge blur of a precision back illuminated 5 degree slanted edge. The back illumination was varied from a contrast ratio of 46:1 to 5900:1. This corresponds to an exposure range of -2 EV to +5 EV, where 0 EV is mid-grey.

The tests were conducted on a Sigma 17-70mm lens (at 50mm) with and without a Kenko Pro 1D UV filter.

The tests show:
1) Veiling glare of the lens, without the UV filter, is negligible at low contrast ratios but increases quickly once the contrast ratio rises above 700:1. This is a 17 element zoom lens.

2) The UV filter contributes very little additional veiling glare up to a contrast ratio of 5900:1.

Conclusions
At normal scene lighting levels, a high quality UV filter contributes little additional veiling glare, in the measurement range of this study.

The primary component of veiling glare is caused by the lens itself. Another study with prime lenses will be necessary to determine whether a similar relationship holds.

Forum: Pentax DSLR Discussion 05-12-2011, 11:08 PM  
Pentax K-7 to K-7...is the K-7 shutter blur enough of an issue to warrant it?
Posted By labnut
Replies: 14
Views: 2,971
I bought my K-7 at the height of the concern. Being a measurement sort of person I set about measuring the effect of Shake Reduction.
More than 1000 tests later I came to the conclusion that there is no inherent design problem. See the graph below. In fact I would say that the K-7 has a very effective shake reduction system.

You can see my full report on Scribd (pdf)
Study of the Effectiveness of Shake Reduction in the Pentax K7
Forum: General Talk 09-22-2010, 01:11 PM  
Center for rehabilitation of whiners
Posted By labnut
Replies: 18
Views: 4,974
Exactly so, experience the joy of taking photos.
Forum: Pentax K-5 09-20-2010, 12:11 PM  
Official Pentax K-5 bashing thread.
Posted By labnut
Replies: 191
Views: 30,422
Yeah, I know, amazing. Some trolls plant their sock puppets well in advance.
Forum: Pentax K-5 09-20-2010, 05:11 AM  
Official Pentax K-5 bashing thread.
Posted By labnut
Replies: 191
Views: 30,422
Yeah, I know, it makes a lot of sense to bash, moan and whine about something we haven't seen, has not been tested and has not been tried out.

But what does it matter, when it has been seen, tested and tried out we will still bash, moan and whine. It is a good substitute for photography.
Forum: Pentax DSLR Discussion 09-17-2010, 11:56 AM  
Poll: Your Criteria for Upgrading Bodies
Posted By labnut
Replies: 38
Views: 5,433
Well, err, umm..., OK, I admit it, of course I want a new toy!
But this primeval drive must first survive some rigorous questioning.

I am impressed that you still use your istD
Forum: Pentax DSLR Discussion 09-17-2010, 11:28 AM  
Poll: Your Criteria for Upgrading Bodies
Posted By labnut
Replies: 38
Views: 5,433
When I think of upgrading I first look at the reasons I bought my existing body then I test those reasons against the following questions

1) Have my needs changed?
2) Have my aspirations changed?
3) Am I better informed about my needs?
4) Have I let myself be unduly influenced by forum mania and marketing hype?

and finally

5) have I used it enough or long enough to get a good return on my investment?
6) are there better uses for my disposable income?
7) will it make me a better photographer?
Forum: Pentax DSLR Discussion 09-17-2010, 11:07 AM  
K-7 seemed nice, but K-5 nicer
Posted By labnut
Replies: 33
Views: 8,504
I most definitely agree with you. I've always found the low light focussing to work just fine on my K7. And in normal light it is quick and accurate.
Forum: Pentax News and Rumors 09-17-2010, 03:18 AM  
Sigma 17-50mm F2.8 EX DC OS HSM - Pentax Mount
Posted By labnut
Replies: 5
Views: 4,082
Yes, indeed. When one takes into account the Sigma lenses as well, lens availability for Pentax is really not bad.
Forum: Pentax DSLR Discussion 09-16-2010, 02:03 PM  
Odd Shake Reduction Failure
Posted By labnut
Replies: 19
Views: 4,169
Jeff, I did a large study on this subject in February when I accurately measured the image blur introduced by hand shake.
Here is a link to the study on Scribd

The graph below shows the most important results.

The top line shows motion blur (in pixels) with the handheld camera with SR turned OFF. Here you can see motion blur slowly increasing at shutter speed of 1/125 sec to 1/30 sec. At slower shutter speeds motion blur increases quickly.

The bottom line shows motion blur with the handheld camera and SR turned ON Here we see motion blur is well controlled down to a shutter speed of 1/8 sec. Bear in mind that a motion blur of 0.5 pixel is a good result.

The interesting thing though, is that the variability in the results increased to 1 pixel motion blur from a shutter speed of 1/15 sec and slower. See the second graph. When the variability increases this indicates that handholding technique is coming into play. The really interesting thing about this study was my finding that I had to rest after every five photos, otherwise the image blur increased quickly. Presumably muscle fatigue was increasing physiological tremor.




Forum: Pentax DSLR Discussion 09-16-2010, 01:12 PM  
Intermittent blurred pictures with K20D
Posted By labnut
Replies: 13
Views: 3,837
Which Sigma 17-70 lens are you using. The newer F2.8 lens has built in Optical Shake. With this lens you must select either OS on the lens or SR on the body but you must not enable both at the same time.
Peter
Forum: Pentax DSLR Discussion 09-15-2010, 12:57 AM  
Odd Shake Reduction Failure
Posted By labnut
Replies: 19
Views: 4,169
Since the problem has not persisted equipment failure seems to be ruled out.
Did you take a lot of photos in a sequence without much rest in between?

When I measured motion blur in my photos I found that after 10 photos or more in a row I was becoming more shaky. Subjectively I was not aware of it but the measurements clearly showed it. Fatigue definitely increases physiological tremor.
Peter
Forum: General Talk 09-15-2010, 12:44 AM  
No respect...
Posted By labnut
Replies: 45
Views: 12,524
Wow, thats seriously deserving of respect.
You won't regret moving to Linux. Did that 10 years ago and I am still glad.
Forum: Pentax DSLR Discussion 09-15-2010, 12:29 AM  
What makes a camera a Pro model?
Posted By labnut
Replies: 56
Views: 9,555
Good point +1
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