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Forum: Pentax SLR Lens Discussion
07-18-2015, 02:10 PM
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That depends on if keeping the Aperture constant means, keeping i the same size, or if it means keeping it at say, ƒ4. Both could be considered keeping the Aperture constant. Not that I care, or have a horse in this race just saying. But obviously a one 1 cm opening on a 50mm lens lets in more light than a 1 cm opening on a 200mm lens. It's collecting light from a much wider angle.
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Forum: Pentax SLR Lens Discussion
07-17-2015, 06:40 AM
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The pitfall of calling this additional light is clear. If you have two equal light sources, turn off one and then open you're aperture you have the same amount of light, but decreased DoF. Just do what everyone else does and say a wider aperture creates less DoF, and there are no exceptions.
SO why not do that? or we could discuss it for another couple of pages. :D
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Forum: Pentax SLR Lens Discussion
07-16-2015, 06:03 PM
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I think Class A wrote something I'm in complete agreement with. Someone check and see if hell just froze over.
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Forum: Pentax SLR Lens Discussion
07-16-2015, 05:03 AM
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No, it's not that much difference, The gain from APS-c pushing 3000/lw/ph going to FF 36 MP hovering around 4000 w'ph, is somewhere in the order of 35%. That's a long way from enough to go up a paper size at the same resolution.
However, printing at 50 lw/ph which would be approx. 100 DPI, you could go from 60 inches to 80 inches, or printing at 200 DPI, 30 inches to 40 inches.
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Forum: Pentax SLR Lens Discussion
07-15-2015, 07:06 PM
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Someone needs to look up circles of confusion. That's all I'm going to say about this. :D
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Forum: Pentax SLR Lens Discussion
07-14-2015, 07:12 PM
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Now I'm going to say you need to watch Tony Northrup, and I never thought I'd say that to anyone. The ƒ-stop controls the intensity of the light hitting the sensor, not the amount of light collected. A twice as big sensor collects twice as much light, if and only if both sense are equally efficient at collecting light.
I guess you missed the part where the longer lens has a much bigger front element and gathers much more light than the shorter lens. :D
If you really know what an f-stop is, then you know its a ratio, a 200 mm lens has to have a much bigger opening than 50 mm lens to achieve the same f-stop.
What about the "equivalence doesn't mean what you think it means crowd," can we come too?"
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Forum: Pentax SLR Lens Discussion
07-14-2015, 12:52 PM
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You guys do realize, that that DxO stuff is purely theoretical? Because they keep saying stuff that's just not true. How many times do they say "assume that". Now go through the whole article and see how many times they say that, then work out the odds of them actually being accurate, because most of it is not true. TO me it's amazing that you guys can take all this theoretical micro-analysis, which may be true in a perfect theoretical sense, but can't be applied in the real world because they've made too many incorrect assumptions. The big scientific phrase missing from the DxO pages. The missing phrase is "if and only if."
The above statement is true if and only if each high-resolution pixel is intrinsically less sensitive. What are the odds of that? See this is DxO. It's not science, it's pseudo science. The fact is, when comparing different systems and, the only thing that matters is "what is the point at which the original signal has been amplified and by how much? That should be critical to determine how much noise the camera will produce. DxO doesn't address it. Because before 800 ISO or whenever it is serious amplification cuts in there is no difference in amplification gain, just longer and shorter exposures. And looking at APS-c and FF , yes you need more light, but you have to use twice as much light to normalize DOF, so much of the time you're in exactly the same boat. If you use half the size pixel but twice as much light to normalize DOF, the light hitting the smaller well is the same, the noise is the same.
And further more, to normalize DoF you'd have to shoot a stop smaller aperture, and that is half the light. SO DxO has done in their example exactly what every FF pragandist has done since the beginning of time. Forgoten to normalize for DoF. Pretend that nothing in the camera system exists but the sensor and that nothing else matters.
What we have here is amateurs getting lost in the minute details of a micro analysis, and missing out on the big picture. That statement I quoted from DxO is absolutely correct, and absolutely irrelevant when trying to understand the difference between two camera systems. Why ? Because there is no analysis of the factors that companies can use to reduce noise, discussion of the sensitivity of various sensors, including the differences between a traditional sensors and a BSI sensors or organic sensors and items of that type. It looks at pixel size in a vacuum.
It's just really sad when people come out and quote it as if it's some kind of absolute fact. That's made possible by omitting that important mathematical construct, "if and only if".
It's a valid explanation of a very small part of photographic hardware, but to have people quoting it as some kind of hard science that actually describes real world systems, that's pretty bizarre. Rather than science, it's more like mathematical theorem, not scientific research into the real world.
It describes one teeny tiny little part of big and very complex systems. And doesn't go into sensor sensitivity, which you would think would be part of the same article, if it were to have any value at all. Unfortunately companies noise reduction algorithms which are also going to have a tremendous affect on this bit of minutia are proprietary and probably beyond the scope of little companies like DxO. They do a good job of measuring the results of the complete system in low light, but have as much clue as to how they got that way as you or I do. Hence when two cameras use the same sensor yet one is rated 7 points higher, they don't know any more than we do. They just tell us it what it is.
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Forum: Pentax SLR Lens Discussion
07-13-2015, 07:54 PM
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There is only one way to understand the difference between lenses used on different formats. Look at images. All this messing around with formulas does nothing. Look at the images and you realize 50mm FF is not the same as 35mm APS-c. It may be equivalent in FoV and DoF with proper adjustments, but in the end, it's just not.
I shoot most of my stationary subjects at every f-stop form ƒ2.8 to ƒ11 and then pick the one I like most. You have to do the same with an equivalent lens in FF or APS-c. And I can't believe you guys don't know your camera systems well enough to see a shot and "go in your head 50mm FF or, 70mm APS-c" That info should come to mind as soon as you see the scene with the camera in your hand. Honestly, if you're doing calculations in your head, I suspect you're missing out. Many times the issue is "what lens do I want to use for this picture" and it has nothing to do with format. There are times when you look at a scene and say "21 ltd." and that's what you want to use, even if you have to walk forward or back, because that lens renders the way you want that image to look. And no the 31 on FF isn't the same. That's the thing I understand least about all this emphasis on formulas and equivalence. I don't think focal length. I think how do I use the lens I think best suits the scene I have in front of me. Working out focal lengths is probably the last thing going through my mind. Accept for the crucial decision on how long a lens I want and how much I want to narrow or expand my FoV, behind my subject.
Of the stupid things you've said, that pretty much takes the cake. But here let me explain it to you again, even though you'll just claim I'm wrong....
When you push film you intentionally underexpose and then over develop. It's a basic technique that was taught in the first year of every photography class, ever. It essentially increases your ISO, and contrast, but also increases your grain size.
I do the same thing in digital, by exposing to the left which is in essence an underexposure, I then use the levels control to make full use of the limited dynamic range I've captured, effectively increasing my ISO, and because of the structure of digital files, my contrast, but also increase my noise, very much like film.
But hey dude, don't bother telling me I don't know what i'm talking about again, I know what you think of me, and so does everyone else. This is for anyone starting out who might be confused by the amount you think you know, that you know nothing about.
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Forum: Pentax SLR Lens Discussion
07-13-2015, 02:17 PM
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All you need to know about equivalence is, if you can take the picture you want on one camera, you can probably take it one format larger or one format smaller, the odds are 95% in your favour. But honestly, most of us know what to do with the camera we have to get the picture we want. Not because we understand equivalence, but because we've spent a lot of time learning our camera. Does the theory of equivalence mean you don't have to learn your bigger format camera? You can just think APS-c and use equivalence? Not at all, you still have to learn your new camera system.
Equivalence is like a coffee table book. GO through it, read a bit of the text look at the pictures... ( no pictures? Toss it.) Pass it on to your cousin. You don't need to read it twice. Understanding equivalence is less that .005% of photography, but thread after thread on the forum.
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Forum: Pentax SLR Lens Discussion
07-13-2015, 12:51 PM
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You said it, not me. You quoted a stat that doesn't equalize for DoF. When viewing at the same size and resolution and DOF, FF has no noise advantage, because it has to give up it's one stop of noise advantage, to shoot with a one stop higher ISO and one stop smaller aperture, to equalize DoF IN that case the smaller sensor, is utilizing twice the light on half the sensor size, the light, total light utilized in creating the image is the same, noise should be the same. Look at the examples above, there is no noise advantage to the larger sensor. Did you even look at the examples? How can you keep saying that, in the presence of real world evidence to the contrary?
Exactly, stop proclaiming "this format is better than that format," for what ever reason, and go shoot some pictures. If you can't prove your point with a few images, you don't have a point. Quit spouting the photo-blog rhetoric. It's sickening.
If someone wanted to post a couple images, one with FF and one with APS_c and discuss their expeience with those images, that would be totally fascinating. This endless parade of people regurgitating web losers whacked out theories has got to stop. Half these dudes are out of their freakin minds. I don't raed them because it hurts me to have to experience such ignorance. Having people post their hogwash on here just sucks. If you think they're so great, go post on their web site. Leave us alone.
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Forum: Pentax SLR Lens Discussion
07-13-2015, 10:33 AM
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I think you need to read the small print really closely to unsderstand what DxO determines.
What about equalizing DoF? The thing the people who make these kinds of statements always leave out.
Let use the K-3 and D750 for examples.....
To get to the same DoF on the D750 you have on the K-3 you'd have to shoot stop slower aperture.
Pixel peeping you get this, the K-3 at 200 ISO, the D750 at 400...
You see the problem, there is no discernible noise in either picture. SO when does this theoretical noise difference kick in? DxO doesn't define the parameters.
You mean it doesn't corroborate DxO's pointless propaganda that's main function is to sell their software? What does that make meaningless? Are you actually saying, don't look at images, listen to DxO and me. We'll tell you what's real?
I'm sorry, but I'm looking at these images taken under studio conditions, and what I'm seeing is no discernible difference in noise and the APS-c image looking sharper because of wider DoF. Now you are spouting some corporate DxO theoretical measurements, that don't mean anything in the real world, to the point you actually advise us not to pixel peep. Because reality shows how insignificant these differences are in the real world.
As for the nonsense that 24 mp of APS-c imagery is somehow different than 24 MP of FF imagery. Look at the images above. What is the difference? Blown up to the same size the APS-c still has the DoF advantage, so what are you talking about?
Where is this magical point where the APS-c image is going to suffer when being printed? All of the sudden those fine looking pixels are going to deteriorate, because they are APS-c pixels, not FF pixels? It's a fabrication. Best case scenario it's an exaggeration, worst case scenario, an outright lie. In both cases, it's not done in the name of science, it's done in the proud tradition of making up scientific mumbo jumbo and double speak, to sell product.
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Forum: Pentax SLR Lens Discussion
07-12-2015, 01:45 PM
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You've corrected nothing.
And glad you like the pics.
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Forum: Pentax SLR Lens Discussion
07-12-2015, 11:03 AM
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I used 50mm on FF and 33 mm on APS_c, how else would you take FoV into account?
Why don't you show us a calculation that does take FoV into account if you're such a genius.
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Forum: Pentax SLR Lens Discussion
07-12-2015, 10:54 AM
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If you're spending this much time on the technical, you're probably not doing the practical.... and you're right, I've seen some technical dimwits who always saw a great angle and got a great image. Being a tech genius in photography makes you pretty much useless, if that's all you've got. Todays shooting. Shoot as much as you can every day... type on the internet when you're too tired, hot and sweaty to do anything else.
K-3 - DA 18-135 -
My grandson is back in Alberta, Tess has gone off to visit her son, and grand niece and grand nephew, I'm just hanging out down at the old swimming hole.
This is what happens when you think you've got the timer set to 12 seconds, but it's set to 2 seconds... you aren't sitting in your chair when the shutter goes.
Tripper diving...
Tia diving..
Misty lost two sticks and a ball, when she gets tired she goes and hides her toy, but then she never goes and gets it when she's ready to go again... see that smile on her face, she saying " I put my toys someplace you'll never find them, but it sure is fun watching you look. "
Blueberries are ripe in some places, but not here...
There's always something happening with the flowers.
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Forum: Pentax SLR Lens Discussion
07-11-2015, 04:29 PM
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So I can use the DoF table.....
Nikon D800 at ƒ4 and 50mm at 10 feet away has a DoF 8' 8.9 inches to 11'8" approx. 3 feet.
A nikon D7000 at 33mm @ ƒ2.8.. and 10 feet away has a DoF of 8' 7.8 to 11' 10" approximately 3 feet.
SO roughly the same.
That's almost a 1 stop light advantage for the APS_c camera if you keep DOF the same.
The faster ƒ-stop you can shoot for on APS-c makes up for the higher ISO you can use on FF which equalizes the noise.
So how does that fit into your theory?
I've never really trusted these DoF calculators but we really need to get you on to some way to check your assumptions.
http://www.dofmaster.com/doftable.html
Do you not understand that the goal here is to equalize DoF, and then see how everything else lines up? If you don't equalize DoF, everything else is nonsense. And that has been the ploy of Full Frame propagandists... if you don't equalize DoF, you can argue all kinds of crazy stuff, that is all smoke and mirrors.
So, is the DoF table wrong too? Everybody is wrong but you? I see how this works. :D
Does the DoF table also put the "ff lens on crop". Well at least if I'm wrong, I'm in the company of some very smart wrong people. :D
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Forum: Pentax SLR Lens Discussion
07-11-2015, 03:11 PM
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Just misleading, and some of the conclusions don't match the data. From a brief glance it seems to be really unclear evaluation of their images, clouded by using too many systems making it harder to understand their point, followed by framing the argument in an unclear manner open to mis-interpretation. Apart from that it's a gem. :D
I mean, if you know your way around this stuff, you can see how this stuff supports your points, if you don't, I don't see how this would point you in the right direction. :D
The noise comparison images showing the differences between the formats is good if you look at the images and don't let the text tell you what to think about them. :D
But hey, we make those kinds of comparisons using the test charts at Imaging Resources all the time. Then I get to choose what two cameras to compare. The cameras they chose for their little demo, I'm not interested in any of them. It makes it a lot harder to read the article. :D
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Forum: Pentax SLR Lens Discussion
07-11-2015, 04:44 AM
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APS_c------------------- FF
IS0 100...................ISO 200 - DR and noise are equivalent
1/100s....................1/100s - shutter speed is equivalent
ƒ2.8........................ƒ4 - total light used by the sensor to create the image and DoF are equivalent.
These images are roughly equivalent (ignoring the 1/3 stop) . There is simply no FF advantage. What you gain in DR and noise, you lose to maintain depth of field, should you choose to go that route. The fact that many have been deluded into thinking equivalence gives an advantage to one format or another is pretty crazy. What FF does allow you to do is to accept less DoF for better noise/DR performance in the rare instance where less DoF is acceptable, should you wish to make that trade. The fact that many have bought into FF based on a mis-understanding of the science is irrelevant.
FF gives you more total light, and higher ISO if (and only if) you are willing to accept less DoF(and at most ƒ stops, APS-c gives you the same trade off, only shooting wide open is there an FF advantage.) . If DoF remains the same, all other features remain constant . That's equivalence. You have to go to extreme measures, as in the article you posted, where they took some really bad low light images, to demonstrate any difference at all. And even then APS_c and FF were practically identical. Sometimes the articles people post, in support of their point, don't actually support their case, as in this one.
The reason they had to use a low light image to show any difference at all, was because they know the difference at high high iSO is minimal to start with. The difference between 100 and 400 ISO on APS_c is minimal, so no one cares if you're shooting 100 or 200 or even 400 ISO. Both on the test charts with their little graphs etc, there is simply no discernible difference. between APS_c and FF until 800 ISO, so between 100-400 ISO, there is simply a theoretical difference, that doesn't actually affect real world IQ.
Or as I've been saying for years, an FF can make a really bad image, less really bad, but it in no way implies you can't get equivalent images with APS-c 90% of the time if you are shooting high quality images.
I feel really sorry for the people who bought into FF expecting really amazing low light images, or even marginally better images. You will get some better images. But in many cases you'll be lugging around heavier more expensive equipment to get the same image.
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Forum: Pentax SLR Lens Discussion
07-10-2015, 07:17 PM
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The focal length doesn't change, the aperture doesn't change, the field of view changes with sensor size, so when you say 17-50 on APS-c is 24 to 75 on FF, you're talking strictly the angle of view.
https://en.wikipedia.org/wiki/Angle_of_view
So just to rehash. Aperture remains the same, Focal length remains the same, angle of view changes.
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