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Forum: Troubleshooting and Beginner Help
03-29-2022, 04:16 PM
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The lens when In the A position allows the body to control the aperture directly, as opposed to manually setting it with the aperture ring.
This permits the use of the following modes with auto exposure
-Av mode
-Tv mode
-Tav mode
- Program mode
In addition it allows the use of
- matrix metering,
-PTTL flash
-HSS Flash
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Forum: General Photography
01-12-2018, 02:50 PM
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A reflex camera does indeed have a mirror that reflects the image from a lens, usually onto a ground glass for precise focusing and composition.
It doesn't have to be the taking lens (as in a Single Lens Reflex), but it can be a separate, viewing only lens, with a reflex finder, like in the Twin Lens Reflex (TLR) type - such as the famous Rolleiflex.
If a camera isn't a reflex type, then it may have a separate glass viewfinder (such as a Leica), or maybe a cheap pop-up wire frame, or an electronic screen that shows the actual image on the sensor (EVF).
I think it was Canon that first started to muck things up back in 1964 or so when they brought out their Pellix: a 35mm SLR, but with a semi-transparent mirror that didn't move out of the way at the moment of exposure. You literally shot right through the mirror. There was much less vibration, and you didn't see any blackout from the mirror going up. Unfortunately, the viewfinder only got about 1/3 of the light, and was noticeably dimmer. And the film only got 2/3 of the light, so it was less efficient.
Semi-transparent mirror cameras were often used for special high frame rate motor drive cameras.
However, Sony resurrected the concept with their SLT models, mainly for supposed AF and live view advantages, but with similar loss of light. It seemed to be more of a stop-gap between true SLR and mirrorless.
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Forum: Pentax DSLR Discussion
07-24-2017, 06:21 PM
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I believe this is an issue with Apple Photos and whether that is totally up to date. The camera EXIF data only contains a code for the lens. It's up the Apple's software (or whatever software is reading the EXIF) to decode the lens ID to give meaningful description of the lens.
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Forum: Pentax Q
12-20-2016, 01:55 PM
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Forum: General Photography
04-11-2016, 01:45 PM
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One important thing to know is that all image stabilization correct for pitch ad yaw. Which is done by either move the image sensor or a lens element in X- and Y-direction
That is the basics of all systems (2-axis or more).
3-axis systems add compensation and motion sensor for roll.
5-axis system also compensation and motion sensor for X- and Y-motion.
The only difference between pitch/yaw and X/Y motion is the type of motion sensor used, but the image sensor or lens element move in X/Y direction for both. The projected image is moving in X/Y direction for both of them. Tilting the sensor do not help for correction yaw/pitch unless the lens also tilt the same amount. But this will not work as a lens may be too heavy and would risk serious damage on the one holding the camera. ;)
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Forum: Pentax SLR Lens Discussion
04-09-2016, 01:34 PM
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Most already do (focal length is an optical property that doesn't change based on sensor size). Manufacturers that place the 35mm "equivalent" focal length on their lenses are the ones that are doing it wrong...
There isn't really any rock-solid way to make it obvious how a lens behaves other than marketing it based on type and feel, i.e. pro telephoto, lightweight wide-angle, etc. And since some such designations could be a bit subjective, official lens names continue to rely on optical properties.
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Forum: Pentax SLR Lens Discussion
04-09-2016, 01:27 PM
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Well, the actual 'true' length is what's labeled. What you probably mean is the ff 'equivalent' focal length.
A 50mm lens doesn't change if you have a different sensor size behind it. 50mm describes the hardware of that lens. It's the smaller sensor that records only a smaller portion of its projected image.
However, I see your point and I agee. Things would be easier if dedicated crop- and micro lenses would additionally show their ff equivalent somehow.
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Forum: Troubleshooting and Beginner Help
02-16-2016, 12:05 AM
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According to Merriam-Webster:
flagship:- the ship that carries the commander of a fleet or subdivision of a fleet and flies the commander's flag
- the finest, largest, or most important one of a series, network, or chain
By (2), K10D, K20D, K-7, K-5, K-3, and K-3II are Pentax's flagship DSLRs. Note that "flagship" and "pro-consumer" are NOT mutually exclusive. The question "such and such is flagship or pro-consumer" is meaningless.
Having said that, who cares whether they are flagships, who even care D7000 or D500 is Nikon's flagship. If you like a camera, buy it; if you don't like it, don't buy it. Why getting hung up on semantics?
___________________________________________________
Added after reading dcshooter's post below and after checking out rlatjsrud's old posts:
I'm sorry for feeding the tr0ll.
Request to Admin: Please give us a way to "thumb down" a post.
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Forum: Flashes, Lighting, and Studio
07-18-2015, 03:17 PM
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Some clarification perhaps required here .... Ambient exposure is controlled by Aperture, ISO and shutter 'speed' .... Flash exposure is controlled by Aperture, ISO, flash power, flash head zoom and flash to subject distance.
So, if all other factors remain equal, then an aperture adjustment will change both ambient and flash exposures, as will an ISO change. A shutter 'speed' change will only affect ambient exposure.
Remember that if using an auto-exposure camera mode (eg P), then all else will not remain equal (auto adjustments will occur to retain the meter exposure value), and in a flash auto mode (eg P-TTL) then all else will not remain equal either as the flash power will adjust in response to maintain the meter flash exposure value.
It is only in M exposure mode and M flash mode that all else will remain equal and it is easy to see the immediate effect of each adjustment.
The reason that shutter'speed' will not affect flash exposure is because the flash light burst is extremely quick .... Perhaps 1/10,000 sec, and relatively very powerful compared to the ambient.(on the things it strikes) ... And it occurs within a shutter time of anything up to 1/180th sec
So it's affect on the ambient exposure is almost nothing because time is not a factor in how much impact it has on the sensor (there's just not enough time). The hole through which the flash must pass (the aperture opening), will of course have an impact on how much light reaches the sensor, regardless of how briefly the light shines for.
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Forum: Visitors' Center
01-14-2015, 02:53 PM
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Set the aperture ring to 'A' and it should work :)
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Forum: Visitors' Center
12-24-2014, 03:53 PM
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So you want to use a 645 lens on your K-3? You can use this adapter, but you wouldn't get AF and you'd have to stop-down meter as per these instructions.
The APS-C vs 645 film crop factor is roughly 2.4x . However, focal length is an optical property unaffected by sensor size. Thus, if you mounted something like a FA-645 55mm on a K-3, you'd get the same exact field of view as from any other K-mount 55mm lens. It would act as a short tele on the K-3 rather than a wide-angle on a 645 body.
Thus, the only practical scenario in which adapting a huge medium format lens would make sense is super tele photography. If only own a long 645 lens like a 400mm or 600mm, rather than buying one with a K mount, you could simply adapt it.
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Forum: Photographic Technique
12-02-2014, 07:35 AM
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Every shot should be in 6x6 format so that we would get rid of articles like this.
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Forum: Pentax SLR Lens Discussion
11-12-2014, 09:39 AM
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No. The lens is actually a 60-250 no matter where its mounted. The 1.5x crop refers to the center of the frame being cropped out because an APS-C sensor is smaller than 35mm.
Focal length is an inherent property of the lens.
The reason it cannot be used on a full frame camera is because the image circle is designed to only cover APS-C. This is so the lens can be smaller and cheaper.
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Forum: Troubleshooting and Beginner Help
11-07-2014, 02:39 AM
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The focus ring can have any values the designers want. This is why old manual focus lenses have a long focus throw (more degrees to turn from minimum focus to infinity). That way manual focus is more precise.
But with AF lenses, you want a short focus throw, because that makes AF faster. It makes MF more imprecise, but the idea is that "nobody uses MF with modern gear anyway." Modern macro lenses might be an exception btw.
Anyway, the numbers listed on there don't matter, you can still focus on everything in between to some degree of precision. Wide angle lenses have a big depth of field, so the difference between focusing 50m and 5km might not be as big as it is with a 300mm lens, which will have a more shallow DoF and will have a noticeable difference between focusing on 5m and 6m. The DoF is shallowest at nearest focus, at lowest f-number, and with tele lenses (high mm number). Notice that most lenses only have distance numbers for the range that the designers assume they will be used the most. Nobody will use a 50mm lens and take photos where 200m and 205m will be critical. But in the near range, 60cm-5m? That is where focus must be very precise, with a 50mm lens.
Tl;dr: If you use AF, just forget it. If you use MF, the distance scales are not as important as the focus throw, which affects the precision of the focusing. But in theory, all distances from minimal focus to infinity should be attainable regardless of the labels.
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Forum: Pentax Full Frame
10-09-2014, 05:15 AM
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Internet misinformation like that just makes things harder to understand for beginners.
Crop factor is an irrelevance. People who regularly switch between different formats will be aware of differences in angle of view and depth of field from personal experience. People who only ever use one format don't need to worry about it.
The assertion that, say, a 50mm f/2.0 lens on "full frame" would become a 75mm f/3.5 lens on APS-C is just plain wrong. It would still be a 50mm/2.0 no matter what camera it was mounted on. The f-stop is the ratio between the lens's focal length and physical aperture size, and using the lens with a different sensor size doesn't change that.
The notion that manufacturers should advertise their lenses with maximum f-stop values based on depth of field rather than exposure is simply moronic.
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Forum: Pentax K-3 & K-3 II
10-06-2014, 01:00 PM
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An 1.4 lens is equal to an 1.4 lens regardless of format. Aperture is not defined by DOF but by exposure. DOF is mentioned nowhere in the definition of a lens aperture.
Different formats are not supposed to collect the same amount of light. Insisting on "equivalence" is missing the point entirely.
Haven't seen the video but all these zealots (who should read up upon exposure theory) do the same mistakes:
1) Insisting that different formats should have the same output and/or collect the same amount of light. This is wrong according to the theory of exposure. If it was correct a Pentax 645 should be compared to a cell phone.
2) Using one format as benchmark; usually FF. This is cheating. By this method only the properties of the reference format is used as properties smaller formats has to comply with. Not the other way around.This is only a one-sided biased opinion. Obviously for two lenses to be DOF equivalent they both have to do the same. Ie an equivalent FF lens must be able to do what the smaller format lens does as well DOF wise to be "equal".
3) Pretending that DOF is only depending on aperture and equivalent focal lenghts. It isn't. It is dependent on aperture, focal lenght, focusing distances, and subject magnification. Ie lenses claimed to be DOF equivalent are patently not. Not even wide open.
Some may be surprised if they put "equivalent" lenses into a DOF calculator. For comperable lenses (eg prime vs prime, zoom vs zoom) you'll find that the smaller format lens usually has thinner minimum DOF than the larger. This is because it has larger maximum magnification.
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Forum: Pentax K-3 & K-3 II
10-06-2014, 10:16 AM
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Sorry, I could not watch the whole thing, Way too much misinformation.
First of all, ISO does mean something, International Standards Organization.
International Organization for Standardization. This organization sets the standards for Light capacity of film and digital cameras. The standard is necessary to ensure the uniform like capacity of all photographic medium. It gives us reasonable transition between film and digital media. Without it, we would be thrown back into the 1700s, when there was no standard for any photographic medium.
Next, It is not the sensor size that determines the Light capacity and noise. It is the pixel size and amplifier. You can have the same noise emitted from a full frame sensor as you can a crop sensor given the same size pixel and Amplifier system.
However he was using the correct math. He just applied it in the wrong place.
It's videos like this that confuse people. People who claim to know what they are doing, and for the most part they do, but apply the knowledge in the wrong way.
I may not be an expert photographer, but I've been dealing with electronics and photography long enough to know that at least some of the information In this video is not correct.
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Forum: General Photography
09-30-2014, 07:31 AM
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A company called Pentax Corporation only existed for 5 years or so. From 2002 to 2007. Pentax existed solely as a brand name of the Asahi Optical Co. from 1957 till 2002. In 2007 it became a brand name of Hoya, and in 2011 a brand of Ricoh.
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Forum: General Photography
08-26-2014, 02:43 AM
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That's not exactly an improvement...
I'm glad there's an ocean between me and american gun culture...
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Forum: Troubleshooting and Beginner Help
07-04-2014, 02:51 AM
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The relevant contacts on the body get shorted through the lens mount (except when this is painted or anodised) and the camera then assumes that you have a stupid dumb old lens on and asks you for the focal length.
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Forum: Troubleshooting and Beginner Help
05-31-2014, 11:11 PM
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The volume anamorphosis (that's a mouthful) of facial features has nothing to do with fisheye lenses* or with flat field optics. What it does have to do with is the rules of perspective which are driven by the position of the lens relative to the subject. Even flat field lenses with excellent rectilinear projection exhibit this feature. What is closer appears larger because it is closer. The only reason the subject appears distorted is that the wide angle lens provides a wider field of view than a "normal" lens at the same distance and allows us to see elements of the subject that are at greater relative distance. You can test this by doing a crop of a "distorted" big nose/chin wide angle portrait and comparing it to a photo taken with a longer lens from the same camera position.
It cannot be stated strongly enough that this is the case for any lens that provides a wide field of view for a particular frame size (format) and is not a property of focal length per se. 28mm is a wide angle focal length on my 35mm film and will provide a very satisfactory duck face when mounted with my KX film camera. The same 28mm lens on my smaller APS-C K-3 provides a fairly flat and boring "normal" perspective.
Steve
* As with all wide angle optics, fisheye lenses will record anamorphosis, but it is unrelated to the lens' optical design which counter-intuitively actually provides less true volumetric distortion of objects at edge of field than a rectilinear lens of the same FOV.
---------- Post added 05-31-14 at 11:32 PM ----------
Sorry I was not more clear :o
It was my intent to affirm and agree with what you had said. My bad.
Steve
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Forum: Troubleshooting and Beginner Help
05-31-2014, 09:07 PM
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The best way to avoid the crop factor head-ache is to forget you ever heard the term. You may also wish to forget you ever heard the term "35mm equivalent" as well. Use this cheat-sheet instead for categorizing field of view:- Less than 15mm = ultra wide angle
- 16mm --> 26mm = wide angle
- 27mm --> 39mm = normal
- 40mm --> 85mm = short tele/portrait
- 86mm --> 200mm = tele
- 200+ = long tele
Steve
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Forum: Pentax DSLR Discussion
02-24-2014, 02:39 PM
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Please "like" this post if you use (or are interested in using) Pentax DSLR's for HDR photography. I own a K-5, and I love that I can shoot 5 bracketed photos. Most similar cameras from other manufacturers only shoot 3, which is often not enough. What other Pentax cameras are others using for HDR?
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Forum: Digital Processing, Software, and Printing
02-12-2014, 07:37 AM
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For print use, you probably don't want to resize - the more resolution the better, generally speaking. Ignore "dpi" and "inches" in photoshop or other software. These things are determined by the printer (since the print limits the dimensions, and that limits the dpi)
For web use you probably want it to be 1000 on the long side (for forums), or 1600 on the long side (facebook, email). Resolution is not important, since every computer will open the photo in its own resolution, depending on its monitor size. The only things that matter is "resize" (number of pixels), and quality (since a low quality will make the photo look worse, but take less hard drive space)
The good thing with raw is that the raw data still stays at max resolution, so you can make as many smaller jpegs as you want.
tl:dr; Ignore inches, centimetres, dpi. What matters is number of pixels and level of compression. Don't resize for print. For websites, resize depending on the website.
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