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Forum: Photographic Technique 06-09-2019, 08:46 PM  
Landscape Hyperfocal / landscape focus advices are wrong
Posted By dms
Replies: 38
Views: 1,534
1. This does not change the usefulness of the concept of the hyperfocal distance, it just means you can adjust the values for the degree of enlargement you use, or "quick and dirty" simply use the usual hyperfocal distance values but use a smaller aperture by a stop or two. Otherwise one does not have an easily used concept for zone focussing, and notwithstanding the above posts, I think simply using infinity cannot be right if there is nearer stuff of import--if for no other reason we tend to look at the larger (closer) things in a picture to assess sharpness--even if it is not the most important stuff.

2. Actually I make hundreds of prints--usually in the range 7"x11" to 8"x12"--for theatre producer/lighting designer/ costume ... That is pretty much what they expect to see and show. And for me (for FL of 28mm and below) I almost always use the hyperfocal distance--for theatre and outdoors.
Forum: Photographic Technique 06-09-2019, 10:32 AM  
Landscape Hyperfocal / landscape focus advices are wrong
Posted By dms
Replies: 38
Views: 1,534
The equation is good for all distances. For hyperfocal distance, it becomes even simpler (since 1/infinity=0), and thus:

d = hyperfocal distance (in this case) = 2 x dc.
Forum: Photographic Technique 06-09-2019, 09:53 AM  
Landscape Hyperfocal / landscape focus advices are wrong
Posted By dms
Replies: 38
Views: 1,534
The proper focus distance is the average of the inverse distances. So if the closest desired distance is dc, and farthest is df, then the optimum d,
is: 1/d = 1/2 (1/dc + 1/df).

Three examples:
dc = 5 ft, df = infinity,
1/d = 1/2 (1/5 + 1/infinity) = 1/10 --> d = 10 ft (as expected for the hyperfocal distance)

dc = 5ft, df = 8ft,
1/d = 1/2 (1/5 + 1/8) = 0.162 ft --> d = 6.2 ft (as expected for far distances focus is 1/3 of the way, which would be exactly 6 ft)

dc = 2 inch, df = 2.2 inch
1/d = 1/2 (1/2 + 1/2.2) = 1/0.478 --> d = 2.1 inch (as expected, for macro the focus is the midpoint)

BTW, if you compare various distances are you using the basis of the hyperfocal distance, which for FF is 8x enlargement (w/o crop) and viewed from 13 inches?
Forum: Lens Clubs 05-27-2019, 10:49 AM  
Fisheye Fever Club -- Flaunt your fisheye photos!
Posted By dms
Replies: 3,294
Views: 584,069
Thanks. The effect (besides the fact that this particular tree is a remarkable specimen, and the use of a fisheye lens) is likely due to:
-- placing the camera only a few inches above the ground, and (thus) strongly angled upwards
-- that it was night with a blend of moonlight and multiple street/house lights
-- and sometimes we get lucky
Forum: Lens Clubs 05-26-2019, 10:40 PM  
Fisheye Fever Club -- Flaunt your fisheye photos!
Posted By dms
Replies: 3,294
Views: 584,069
The attached photo is with the F17-28mm fisheye at the widest FL. I am new to this lens, but I find it potentially very useful as it can give full fisheye with FF and very wide/mildly fishy (image) on cropped sensor. Attached is an example of the latter, in which I used Photoshop's transform warp function to make the horizon reasonably level w/o affecting the tree's limbs.
Forum: Post Your Photos! 05-07-2019, 08:41 AM  
People Almost Monochrome
Posted By dms
Replies: 6
Views: 250
Wow. Great image.
Forum: Pentax Price Watch 05-06-2019, 11:59 PM  
New B&H Offer: Pay no sales tax through reimbursement w/ Payboo card
Posted By dms
Replies: 35
Views: 1,608
There is another problem, in effect customers in non-taxing states will be paying a tax. As B&H will have a price to charge that reflects their bottom line, and if they are giving x(%) back to half their customers, then the price will be x/2 higher to everyone.
Forum: Pentax Price Watch 05-06-2019, 10:53 PM  
New B&H Offer: Pay no sales tax through reimbursement w/ Payboo card
Posted By dms
Replies: 35
Views: 1,608
As my shipping address represents me, I don't see the distinction. In any event I was just expressing my (low) opinion of what is being done. In the end the legal aspect will be decided by the courts, the ethical question will likely not.

And (BTW) if all the other major internet dealers do the same, it is another nail in the coffin for physical stores, and thus even less chance to try out gear before buying same.
Forum: Pentax Price Watch 05-06-2019, 09:39 PM  
New B&H Offer: Pay no sales tax through reimbursement w/ Payboo card
Posted By dms
Replies: 35
Views: 1,608
I am no lawyer, but this seems legally wrong and ethically wrong! One of the problems I have is how can one divide the clients up into groups where some get a price reduction and others not. Could just as well do it based on one's religion (instead of state).
Forum: Troubleshooting and Beginner Help 04-19-2019, 03:52 PM  
Sunny 16 rule and my Pentax K1000.....
Posted By dms
Replies: 30
Views: 1,321
A cloudless stretch of blue sky with the sun above 45degrees and not near the area measured, should match/be very close to the sunny 16 rule. Indeed this is the usual way to calibrate a (reflected light) light meter. The reason it works is because the blue sky is a midtone.

Actually camera meters may be off, and an older lens w/ lots of elements would have a larger light loss (reflected light on the elements), to name two differences. It is quite common for minor differences--so take another reading of the blue sky and see what the exposure is that it give, and if only 1/2 stop difference it is minimal unless using slide film. In any event I would bias the ASA value you input so it gives sunny 16 rule when properly metering the blue sky, and use it and look at the negatives, and w/ some experience (if need be but unlikely) input a new adjusted ASA (ISO) value to better correct things.

But the bottom line is the metering of the blue sky is the best (and really only) practical method we have to check the light meter. As comparing to another light meter assumes the other one is correct--which is not a known.
Forum: Pentax DSLR Discussion 04-18-2019, 10:18 PM  
Will a different focusing screen help?
Posted By dms
Replies: 38
Views: 1,469
It was both, A lens if the open-aperture reading and K lens if stop down, as It is the aperture at which the exposure determination is being made, and not the aperture that will be used, that determines the exposure adjustment. You may be right about the blacking out at f/8, I only really used the spot metering for theatre photo's and in that scenario I was never closed more than f/5.6, and usually f/4.

As regards off topic, there was (were) comments about the debit side of the replacement screen being the inability to use spot metering reliably. My point is to say it still can be used, with some additional adjustment.
Forum: Pentax DSLR Discussion 04-18-2019, 07:30 PM  
Will a different focusing screen help?
Posted By dms
Replies: 38
Views: 1,469
Since above I mentioned the adjustment to spot metering w/ a fosusingscreen.com screen (K3 w/ grid) in my K20D, I checked my summary notes from the tests, and I had the following. I was metering a midtone (Kodak grey card) and I recall using several lenses and finding similar results with each of them.

Table. Required adjustment in e.v. (vs. lens aperture)
f/2.8** . . . 0
f/3.3 . . . . -1
f/4 . . . . . .-2
f4.7 . . . . .-2.5
f/5.6 . . . . -3
> f/5.6 . . .-3

As a happy accident, this means if you set your exposure by spot metering the brightest area in the scene, no exposure adjustment is required at f/5.6 and above.
_____
** I also recall needing a + adjustment at wider than f/2.8, but I don't find that in my abbreviated notes.
Forum: Pentax DSLR Discussion 04-18-2019, 04:51 PM  
Will a different focusing screen help?
Posted By dms
Replies: 38
Views: 1,469
I found the adjustment to spot metering (on K-20D) was a (reliable) function of f-stop. I have forgotten now as I don't use the camera where I installed the screen much. It is focusingscreen.con product, based on Nikon K-3 screen (ruled with lines and no AF markings) as I recall. It was something like reduce exposure 1 stop at f/2, spot on at f/2.8, minus 1 stop at f/4, minus two at f/5.6 and above. You can easily test a lenses (or lenses) and work it out.

About price, it is about $75.00 (US) and then shipping. Once you have it, it is possible to scratch screen, get dust in, and may need to shim it. For me I think a price of about $50 for someone else to install it would be an attractive alternative.
Forum: Pentax Film SLR Discussion 04-18-2019, 09:59 AM  
Blue haze on landscape shots - help?
Posted By dms
Replies: 22
Views: 1,267
I also see it as too pink/too warm. The skylight filter is /should be used to adjust for too much skylight, and on a sunny day it would make the temperature too low (too red). But the operator doing the scanning could have done a better job of adjusting the color balance.

The atmospheric haze is there, and as noted above is due to UV light--the higher the elevation the more UV is present. Atmospheric haze nevertheless is generally there, and the good thing is it suggests what things are very far away, and thus we know the mountains are mountains and not close by hills. A stronger IUV filter or a polarizing filter may help--try them (next time do a test w/ weaker UV, stronger UV, and polarizer). (Used UV and linear polarizing filters are often inexpensive as less used with digital.)
Forum: Pentax SLR Lens Discussion 04-16-2019, 03:09 PM  
Advice on first M42 Wide Angle lens.
Posted By dms
Replies: 27
Views: 1,096
Sounds high. KEH has an SMC 28mm f/3.5 SMC Takumar for $84.00 (US).
Forum: Pentax SLR Lens Discussion 04-15-2019, 08:42 PM  
Advice on first M42 Wide Angle lens.
Posted By dms
Replies: 27
Views: 1,096
Of course it depends on what focal length you will find works for your eye. And that comes from looking a images taken with various focal lengths and your own usage/experience.* But since you asked:
-- I found 35mm was fine with film, for landscapes over maybe 3~4 decades, and only with digital did I gradually go wider and wider, to the point where now maybe 1/3 of my landscapes use fisheye lenses.
-- But I think it is related to digital and the control one has versus film where (for me and most of us) it was the slide, or the prints from the store that did the developing. With prints I often collaged them by pasting them on a board, which was in some ways more arty/rewarding than digital processing.
-- So I would say either the Pentax Super (or SMC) Takumar 28 mm f/3.5 or 35 mm f/3.5 ** are good choices (I have both of them, and they are excellent, although the 35mm f/3.5 is considered by many to be one of the best lenses, it really is unimportant--they are both very good.) Neither of mine are SMC (multi coated) and they do fine (although I always use a lens hood--actually with all my lenses--SMC or not).
-- But the 28 mm is quite bit wider, and thus is more difficult to use (near far relationships become more critical and w/o them the pictures can look flat), thus I would start with the 35 mm f/3.5. Although there are many good lenses I think sticking w/ Pentax for this makes good sense. Also Pentax lenses generally age very well!

_____
* I actually went through Ansel Adams book (Camera and Lens) and noted for each picture what the equivalent 35mm focal length it was, and a significant number were close to 35mm, and perhaps surprisingly very few were wider.
** Late Super Takumar 35mm f/3.5 lenses apparently were SMC, but not stated as such.
Forum: Homepage & Official Pentax News 04-14-2019, 10:21 AM  
Pentax M, FA, and D FA* 50mm F1.4 comparison
Posted By dms
Replies: 15
Views: 941
Yes, thanks for the correction.
Forum: Homepage & Official Pentax News 04-13-2019, 08:51 PM  
Pentax M, FA, and D FA* 50mm F1.4 comparison
Posted By dms
Replies: 15
Views: 941
My DA 20-40 mm limited has no aperture ring and has DOF markings for the 20 mm FL (although the limited rotation of roughly 90 degrees makes things very cramped). And even if it wasn't possible it is a consideration in comparing the three lenses.
Forum: Pentax SLR Lens Discussion 04-12-2019, 05:43 PM  
Can't get a filter off
Posted By dms
Replies: 20
Views: 863
It makes little sense, but I have found I couldn't remove a filter, then I put the lens aside, and later tried and w/o real effort it came off. Go figure!
Forum: Homepage & Official Pentax News 04-11-2019, 08:35 PM  
Pentax M, FA, and D FA* 50mm F1.4 comparison
Posted By dms
Replies: 15
Views: 941
It would appear the DFA does not have DOF markings, which would be (for me) a significant consideration/oversight.
Forum: Photographic Technique 04-04-2019, 09:03 AM  
Spot, Weighted and Matrix metering, is it the same as EV Compensation?
Posted By dms
Replies: 39
Views: 1,631
As long as you understand what center weighted (or with separate light meter averaging) is looking at, and you can reasonably estimate with experience how much brighter and darker areas there are (both how much darker and lighter, and what fraction of the scene) you can reach close to the same setting as by using spot meter to measure various parts of the scene. With experience whatever metering method you use gives essentially the same result. That even is true of simply estimating the exposure based on the older "cheat sheets" given with film, and using experience from similar images taken (e.g., I find metering of little use in evening with many far off strong lights, and then use my older experience).



As to there being no right exposure, in some cases that is exactly right (here we differ with some of the comments posted). While with many images you want to capture the entire dynamic range and then can pp to get the look you want, where the DR is too large you pick the slice that you want, letting brights being blown out/featureless or letting darks be featureless. Although even where the entire DR can be captured, if you know you want for example to have a rich darks and blown out very light areas, you could/should purposely overexpose so you will have less noise in the areas you are most interested in.
Forum: Photographic Technique 04-03-2019, 10:13 AM  
Spot, Weighted and Matrix metering, is it the same as EV Compensation?
Posted By dms
Replies: 39
Views: 1,631
As said above, matrix metering is making an exposure adjustment by rules that probably give good results for typical scenes, but one does not know what the rules are it uses, and you should be able to meter the scene and then adjust based on what you conclude is needed--e.g. a scene with bright areas due to reflected sunlight of the ocean should be metered/adjusted to ignore this.

Ultimately it is about understanding exposure theory, and studying this will give huge benefits down the road. I really like "Exposure Manual," 3rd ed., 1974, by Dunn and Wakefield. Also Ansel Adams "Camera and Lens" (although we don't expliciely use his zone system, the way of looking at a scene in terms of zones is still valid/useful). They both [Dunn and Adams] discuss exposure meters (incident, spot, averaging) but that is less important than exposure in terms of mid tones and balance of light to dark areas.

These older books tend to also treat (practical) exposure theory, as opposed to (only/largely) saying use matrix here and use spot here, and so on. I have no idea if there are good current books on the subject--the few I have looked at are about mechanics and not practical exposure theory.

For what its worth my usual method for outdoor street/architecture work is as follows.

-- Full sun: sunny 16 rule (adjusted for whatever f-stop I set) in manual mode. This is actually a very tough scene to meter w/ camera but easy w/ sunny 16 rule or incident light meter.

-- Other: usually AV mode, center weighted, and set ev compensation based on my perception of scene proportion of light/dark areas and whether I want to bias exposure for lighter or darker areas.
Forum: Pentax Q 03-27-2019, 07:41 PM  
QS1 wide lens options
Posted By dms
Replies: 12
Views: 627
BTW, attached is an example with the 04 lens on the original Q (so FF equivalent of 35 mm, not the 29 mm on the Q7/QS1).
Forum: Pentax Q 03-27-2019, 07:33 PM  
QS1 wide lens options
Posted By dms
Replies: 12
Views: 627
I find the Q system's no.3 and no.4 lenses to be fine, where the intended use is sufficient lighting and not large enlargement--8"x12" is certainly fine. And the Q and both lenses easily fits in a typical sport jacket pocket.

--The 03 fisheye is an interesting approach to very wide. If you look at my review of Imadio Fish-eye hemi software you will see an image taken with the original Q and the (No.3) fisheye lens and then pp with fisheye hemi. It provides a good (very) wide angle image. I really like the fisheye hemi way of adjusting the fisheye look to a normal one; however, it is a plugin to photoshop, photoshop elements, or lightroom (maybe few others?). I don't know, but as a rough guess, the resulting image on the QS1 is likely about FF equivalent of 18mm.

-- The 04 lens is a 29 mm FF equivalent on the QS1/Q7, and while much maligned, I think it is quite good.

And the QS1 you have and the fisheye lens can be purchased new for around $65, and Fish-eye Hemi software for $30, and the 04 for about $40.
Forum: Pentax K-1 03-20-2019, 08:19 PM  
Shutter shock with small primes
Posted By dms
Replies: 48
Views: 2,066
How the mass distribution/its nature affects things can be hard to know, but it may be useful attaching a mass to the K-1. For example a tripod head and/or the battery grip (you mention the monopod helping). Whether you actually want to carry the camera that way is of course relevant, but still it may be useful to know/be a fall back. Also I would think how you hold the camera would have an effect, as the hands (and possibly the face) should be able to absorb quite some recoil.
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