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Forum: Pentax DSLR Discussion 03-27-2017, 06:57 PM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
Ya, the list of APS-c primes for landscape, and even zooms isn't all that impressive, unless you look at what's available for the K-1. Then it's really impressive.

I looked at the numbers for the 15-30 today, well over 1 kg (or 2.2 pounds.) Pentax is starving me here. Nothing consumer below 28mm. The other day at Ragged Falls, Tess took my 8-16, I took my K-1 and 28-105, guess who got the shot of the day? I have summer coming up with many trips already planned. What hasn't been decided is what's going with me. If there's no K-1 ƒ4 WA lens by then at a reasonable price, itthe K-1 will be stating home. It's as simple as that. I can work with 24 MP instead of 36 MP, I can't work without my Sigma 8-16, 21 ltd. and 18-135 and DA 200 and TCs.

I know it doesn't hurt Pentax, that I leave my camera home, but it does beg the question, if I bought one, and have to leave it home, why would anyone else buy it? I can take the 8-16, 18-135, 200 and two TC and 50 macro an have a complete kit, that goes right to 476mm APS-c or the equivalent of 700mm on the K-1. SO, I'm better off for long lens work and wildlife, I get a much less capable walk around lens. And there's nothing the equivalent of my 8-16 (which would be 12-24 on the K-1.)

I wonder how many more years the K-1 will be staying home on trips. Someday, I'll find a Sigma 12-24 in K mount, hopefully. I bought the K-1 to be a landscape camera, but I don't need and won't pay for ƒ2.8 in either weight or price. Pentax has not a single wide angle in production for me.

But there I go whining again. :D
Forum: Pentax DSLR Discussion 03-14-2017, 11:43 AM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
What are we talking about again? :D

I plead the fifth, even though I'm Canadian. :D
Forum: Pentax DSLR Discussion 03-14-2017, 04:57 AM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
Let's not start talking crazy.... :D

---------- Post added 03-14-17 at 07:58 AM ----------



That's what I like about this place, there's no excuse for making the same mistake twice. Someone corrects you the first time. :D
Forum: Pentax DSLR Discussion 03-13-2017, 07:20 PM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
Pwesonally just abandoned the former Pentax W series, now the Ricoh WGx . I got a Nikon Coolpix 130AW for $200 CDN. I loved my WG series cameras, I still have one, that won't keep the time and date anymore after being submerged under a skidoo trail/swamp for three months. But they were twice the price, and money is money, and Ricoh hasn't done much with it lately. Some reviewers are refusing to review the new one, saying it isn't any different than the last one, and because 1.5 seconds between images is ridiculous in this day and age.
Forum: Pentax DSLR Discussion 03-13-2017, 06:04 PM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
1. Well no, K-3 has more pixels than a 6D, a Lumix DMZ1000 one inch sensor has more pixels than many old Canon Full Frames.
2. Huh?
3. How does the Lumix with a 1 inch sensor out resolve a Canon 6D?
4. The functionality to a shorter lens registration has not been established. There's a lot of evidence this is just manufacturer hype. The Pentax registration is 43mm. So you can make a fairly compact 43mm lens, like the 40XS. Longer and shorter you have to design the lens to be functional with a shorter or longer registration distance. Moving that point doesn't change anything. You still get heavier and need more corrections, the further you get from the registration point. It has been suggested , again, by the manufacturers that the short registration makes a difference. They also claim that if you should buy their camera, whether it's appropriate for you or not. Believe they have your interest at heart if you must. The only advantage I can see to a shorter registration distance is you can tell folks that with an adapter they can use their old favourtie lenses, and then try and get them to buy something of their manufacture after they make the purchase and realize what a crappy solution that is.
5, Then why does Sony and other short registration cameras have in body lens correction, just like Pentax? It's not because they can reduce the problems of distortion by changing the registration distance, they already did that.

Not trying to be too hard on you, but a lot of this doesn't make any sense. My personal guess is that the problem of the angle of light created by a short registration distance affects way a sensor absorbs light. That's why you see pictures of a Sony 70-200 mounted on an A-7 and it looks the same as any other 70-200 on any other camera.. IN fact it looks like they created a standard 40-44mm registration distance by putting a spacer in the lens, creating a 40-44mm registration distance even though a true native lens would mount right on the camera body with no spacer. They did that for a reason.

You really need to make sure there are no real world examples that contradict your hypothesis before posting this kind of thing. But keep plugging. Once you understand it, it's simple. Mind your lw/ph, and find a lens you love. Buy the camera that goes on it.

Or to make it even more simple, take lots of pictures. Try to figure out what's wrong. Take more pictures. DOn't worry about the theory. You can learn to be a great photographer without intellectual knowledge of the process. You can't become a great photographer without tons of experience shooting pictures. If believing there is some kind of benefit to short registration gets you going, go with it. As long as it keeps you shooting with confidence.

But, I don't see the Pentax registration distance as a problem, and niether does anyone else except maybe some short registration manufacturers. And they just want your money.
Forum: Pentax DSLR Discussion 03-13-2017, 12:13 PM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
The K-3 is better at landscapes than the K-1 is at doing birds and wildlife. If it came down to what I'd miss most it would be the fast frames per second rate, but more importantly the 23 shot buffer, and the speed at which the buffer is cleared. For small birds and wild life those things are really important. 3600 lw/ph instead of 2700 lw/ph is barely noticeable in most images.I never print more than 20x30. 90 distinct line per inch using a K-3 or 120 distinct line per inch using a K-1. It will be barely noticeable in most photos. In fact we have trouble telling the difference between the difference between a K-5 and the K-1 in everyday images. 1/90 is .0111. 1/120 is .0083. .0111-.0083, is .0028, or approximately 3 thousandths of an inch. It's amazing how many people think that will make a huge difference to an image. From 5 feet, you can't even see .003 of an inch.

You get slightly less quality with a K-3, but you get a lot of images you won't even get with a K-1. And I swear the K-3 clears it's 23 shot buffer faster than the K-1 clears it's 8 shot buffer, although maybe it just seems that way, because you rarely fill the K-3 buffer, but I consciously slow my frame rated down to probably about 2 frames per second with the K-1 to avoid filling the buffer. To many times I've sat there and watched as good images went by, waiting for my buffer to clear. It's a big performance hit. The K-1 has some advantages to be sure, but for me they don't make up for it's shortcoming in speed.

But when I'm out on a hike doing maybe landscapes or sunsets or whatever, I don't need the high frame rate and the superior Dynamic range, better high ISO performance, superior resolution and many other features, make the K-1 the one to have. But my K-3 is still in the holster with the DA*200 with the 1.4 on it and the 1.7x close by, incase I need reach and speed.

It's just a question of what you are prepared to live without. And I can see 99% of the Pentax shooters, making the opposite choice. It's all about what makes you happy. Reality says, you get many more photo ops for stationary objects than you do for living, moving targets. For stationary targets the K-1 and 28-105 is an amazing combo. But for the difference it makes, I won't give up the other things that the K-3 has that the K-1 doesn't. Speed, and magnification.

I did say the K-1 gets more use. I spend more time with it in my hands, but out in the blind shooting the little birds or in the park shooting wildlife, I may shoot 500 images in a single session. I'll spend a lot of time with a K-1 in my hands before I get 500 images. 60-120 per session is the average.

As I said previously, you need both. :D
Forum: Pentax DSLR Discussion 03-13-2017, 07:23 AM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
I don't even like to make exact copies of my own photographs, forget about someone else's. You take the optimum photo for the format you use. What someone else is doing on a different format is irrelevant. Which format is more appropriate to the scene is completely a crap shoot. But given that most of us only carry one or two formats, odds are, we are using something less than the optimum format most of the time. We just pick our poison and live with it. :D

The " FF is the greatest thing since sliced bread" with all the justifications about narrow DoF resolution etc, arguments were a great disservice to photography. People who really know photography will be able to expand upon the strengths and weaknesses of every format and explain their place on a continuum in various categories, resolution, low light performance, weight, DoF ( meaning wide, as well as narrow DoF) etc. You own't find them going on about one format being "better" than another. To do so, you have to ignore an awful lot of reality. One might be better in one small area, but it's not going to be better in all of them.
Forum: Pentax DSLR Discussion 03-13-2017, 06:12 AM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
I use fast glass only for shutter speed when I need it and to improve my auto-focus performance.. Depth of field equivalence is not a concept I care about one iota. I almost always expose for maximum resolution expressed as lw/ph and maximum depth of field. That means ƒ5.6 on most and APS_c and Full Frame lenses, although with the best lenses it can be ƒ4 and even lower. The only time I shoot a wider aperture is when low light forces me to. And in those situations ƒ4.5 is much worse than ƒ2.8. FF is a little more tolerant maintaining lw/ph going to ƒ8 than APS-c is, so I often shoot ƒ8 on FF. It maintains both maximum DoF and maximum lw/ph, without seriously crippling my shutter speed in bright sun. In shade ƒ4 and even sometimes ƒ2.8 become necessary to prevent subject motion blur.

So, no ƒ4.5 on FF is not ƒ2.8 on APS-c. AF systems are usually calibrated for ƒ2.8, on both FF and APS-c systems. To get the most out of your AF you need ƒ2.8 glass in many cameras, and all Pentax systems as far as I know.

I say this for any who might be reading. Ian thinks differently. I've been through this with him many times, and he remains stubborn in his opinion. I wouldn't expect him to change now, so expect a response explains how wrong I am, that ignores, that sensors are tuned for 2.8 AF, that Aperture refers to the intensity of light transmitted, not depth of field, and that shutter speed is a big factor in selecting ƒ2.8 glass for wildlife and birds in flight.

He will argue that the only important aspect of aperture is depth of field. Or maybe he won't since I've already explained his point. :D
Forum: Pentax DSLR Discussion 03-12-2017, 06:51 PM  
understanding the 1.5 crop factor
Posted By normhead
Replies: 37
Views: 4,674
I was with you until the "enlarged more" thing. Native resolution is huge on most APS-c cameras, At 100 dpi like your computer screen a K-5 image is 50 inches wide, a K-3 image is 60 inches wide, a K-1 image is 70 inches wide. In actual fact, 99.9999999% of images are reduced to a smaller size for out put. In the old days, you had to enlarge the negative more for the smaller format image to be the same size, also enlarging the grain twice as much and often creating visible grain. With digital the smaller format in this case APS-c has to be reduced less. The difference being with film, you're grain just got larger and larger. With digital the noise gets smaller and smaller and in many cases disappears completely, as you reduce an image.

The point at which a K-1 is the same as a K-3 image is probably at about 5000 pixels wide. You don't have an output device that wide. Printing at 200 dpi, you'd still have to print over 25 inches wide to see a difference, as a guess, it may not even be apparent then.

So essentially, when shooting a 24 MP full frame, and a 300mm lens ƒ2.8 , and a 24 MP APS-c with a 200mm ƒ 2.8 lens, you will have the same field of view and same resolution, in essence, identical images. Both will suffer the same amount of enlargement to print them big. That's why people say the APS-c gives you more reach. What's the difference You ask? Well it's the difference between this and this for the same image. We are talking a 3 pound total package against an 8 pound total package. One manageable one not.



This is the extreme example, showing how bad it can get. But most folks don't shoot either 200mm or 300mm so as a comparison it makes no difference. But on the whole APS-c lenses are lighter, and smaller for the same field of view.

You've got a 300mm equivalent lens for the price and weight of a 200mm with APS-c. And neither image is reduced or enlarged in size, any more than the other when viewed on a computer or printed. Once they are pixels, sensor size has nothing to do with it, (at 100 ISO, at least) in terms of enlarging or reducing.

But as Pentaxians, our FF is 36 mp, so it's a lot more complicated. You have to add Pixel Density to the equation. If there were a simple way to figure this out I'd have done it. And I haven't. But here's how much you have to crop a K-1 image before you could have taken a better image with a K-3.



The best measure of resolution for Digital Cameras is lw/ph, line width per picture height. It's the largest number of distinct lines the sensor could display if you took a picture of alternating black and white lines. It is in no way equivalent to MP. The K-1 is measured at around 3600 lw/ph tops with a great lens. A K-3 is measured at about 2700 lw/ph so the K-1 has roughly 33% more resolution, with 50% more pixels.

But a Panasonic Lumix DMZ1000 with a one inch ( 1/4 the size of APS-c) sensor can produce 2700 lw/ph just like a K-3. That little 1 inch sensor can take images equivalent to your APS-c camera at 100 ISO. (It loses lw/ph very quickly as the ISO goes up , but hang in with me, that's irrelevant.) That little sensor can produce images as good as any K-3 and better than a 22.3 MP Canon 5D mk3 FF costing 3 times as much.

So just to summarize. As has been pointed out above, the easiest thing to do, is look through the viewdifinder, take the picture you want with the camera you have, and do what you do with it. It is very unlikely that you are going to push the limits of your camera, no matter what you are shooting. And if someone is going to figure out a formula taking into account, sensor MP, real sensor resolution and sensor size more power to them, but bottom line, in digital, sensor size and MP are probably the least important things for understanding resolution or enlargeablilty.

The lw/ph is really the only thing that matters, and that exists independent of sensor size and MP, which at least IMHO opinion are at best unreliable measures of resolution.

Here's an example.


In this case, in terms of printing. the 1 inch 20 MP sensor will produce an image equivalent to a K-3 image, with a smaller file. There's a reverse magnification effect. The Lumix will give you the same resoluiton with a physically smaller image, based on how good it's sensor is at converting MP to lw/ph. The Lumix at 100 ISO will actually out resolve a Canon 5D mk 3 FF, 22 MP sensor.

You also need to take into account that different sensors in different systems lose lw/ph at different rates as the ISO increases. So, while you can might get the image you want with a smaller sensor, as the ISO climbs it will very quickly fall behind the larger sensor, as well as the Dynamic Range and noise levels.

If you don't have a headache by now tough, I do. :D
The only things you need to understand with crop factor is, the more crop, the shorter lens you use to achieve the same Field of View.
As general rule, the larger the sensor the better it will be in low light.
A full frame camera gives you narrower depth of field and smoother out of focus areas if you need that, and APS-c isn't good enough. (many of us find APS-c quite good for narrow depth of field images.) FF is the most overall versatile format in digital but only because it's too expensive to build faster than ƒ2 with ƒ2.8 being more common lenses in Medium Format, and 1.4 can be common in FF, and 1.2 is available. But MF will still produce the highest resolution.

Full frame is the format where it become physically prohibitive to build fast glass, for the next format up. It's in a physical sweet spot. But smaller systems can be just as useful to you if not better depending on what you do. Unfortunately landscape and wildlife are on two different ends of the spectrum. A slow snails pace camera like a K-1, D800 or 645z s great for landscape. Not so good for wildlife. K-3s, D7200s, D 750 or Canon 1DXs and many other 20-24 MP cameras are better for wildlife, with their faster frame rates and deeper buffers.

You really need one of each. :D

And you can know all this stuff, and still have trouble finding a camera you actually like. :D

Liking the camera and how it works is probably the most important thing. :D
Personally, APS-c is my favourite compromise, but my most used camera is the K-1, and i would buy them in that order. But I shoot a lot of small bird pictures and wildlife. If you don't or landscape is more important to you, you might go at it differently.

Aren't you glad you asked? :D
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