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09-08-2016, 03:58 AM   #1
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Film equivalent size

Ok, put this in the stupid question category if you want and lol (quietly please)

1 since I am using a dslr, either a K 3 or K 5 II, instead of a film camera there is a factor that is used to get the equivalent film size of the lens you are using, correct?

2 What is it - 1.5, 1.25, 1.4, 1.75 ??? for my specific camera bodies???

3 You then multiple the factor times the focal length of the lens, so as an example, a 200 mm lens becomes a 300 mm lens? (200 x 1.5 = 300), is that correct

In other words by using a dslr instead of an old film camera you have a built in teleconverter?

Thank you for laughing so quietly

For bonus points why is this done?

09-08-2016, 04:05 AM   #2
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it's the 'equivalence' factor you are looking for; your APS-C sensor is smaller than the FF sensor, so your lenses give you a field of view equivalence - it doesn't change the focal length, only the field of view...
09-08-2016, 04:07 AM   #3
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The Crop Factor Unmasked - Articles and Tips | PentaxForums.com

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09-08-2016, 04:10 AM   #4
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This should also help.
The Crop Factor Explained: An Animation - Tutorial Videos | PentaxForums.com

09-08-2016, 04:10 AM   #5
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For all except the Pentax K-1 (which is the same as 35mm film), the Pentax DSLRs have a crop factor of 1.5; they see the world through a narrower perspective, so a 100mm lens gives you the field of view that you would get from a 150mm lens on film.

You aren't actually getting any extra "zoom"; you're effectively cutting the edges off a normal "film" picture. But if you enlarge what's left to the same size as the original print, then you get an "apparent" zoom.

The fact that modern APS-C DSLRs have remarkably high pixel densities relative to their predecessors enables you to do this without losing significant detail (to a point). If all you print is pics to go in frames or a photo album, you will not see a difference; if you are printing huge wall-size murals, that is potentially another matter (depending on how closely they are intended to be viewed - looking at things from a distance diminishes pixellation and "grain" effects as the eye perceives them).

Why is it done? Not sure. For a given size of pixel on the sensor, it is cheaper to build a crop sensor and the camera can be smaller and lighter, all else being equal. The trick is determining where that reduction in sensor size starts to bring penalties in image quality and low-light performance (again, all else being equal) - Nikon and Pentax decided a crop factor of 1.5 was appropriate, while Canon went with 1.6. Micro 4/3 cameras (Olympus, Panasonic) have sensors with a crop factor of 2, but they were later to market and benefited from improvements in sensor technology which mean that their images really don't suffer all that much for everyday casual usage, and there are some pros who can get away with it too, depending on exactly what they are shooting and how well they can control their lighting.
09-08-2016, 04:18 AM   #6
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Thanks for the quick responses and for laughing so quietly

Actually between the time I posted my question and now I discovered the area of the forum that I needed to be reading

So moderator the choice is yours, I'm ok with deleting this thread or if you think that others would be aided by my "stupid question" leave it up

I've learned that I need to just "go with the flow" and not to worry about it

Once again thanks to all
09-08-2016, 05:04 AM - 1 Like   #7
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It's not a stupid question (the stupid question is the one that doesn't get asked!), and happy to leave it in place
09-08-2016, 05:20 AM   #8
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QuoteOriginally posted by Aslyfox Quote
Thanks for the quick responses and for laughing so quietly

Actually between the time I posted my question and now I discovered the area of the forum that I needed to be reading

So moderator the choice is yours, I'm ok with deleting this thread or if you think that others would be aided by my "stupid question" leave it up

I've learned that I need to just "go with the flow" and not to worry about it

Once again thanks to all
Not to worry dude, I had my *ist for 3 years, before I even found out it wasn't 35mm. I just assumed, it's a Pentax digital, it's about the size of my Program Plus.... I wondered why my FA 50 1.7 seemed to be longer than before.

But go with the flow works for me. Look through the view finder, what do you see, want wider, get a wider lens, want longer, get a longer lens, or just forget the whole thing and get an 18-135. The whole idea of one sensor 36x24 being some kind of true sensor and anything smaller being a "crop" sensor is just complete photo enthusiast hogwash.

It did get started in film days when most DSLRs were FF and some manufacturers started coming out with "hafl frame" cameras. And thanks to the movie industry at some point 35mm negs started being called frames. But in the current context, with so many great cameras made in so many different formats, picking 36x24 to be called "full frame" is disingenuous. It really is just marketing hype, and enthusiast "my camera is better than yours" nonsense.

The difference between film and digital would be that on digital you can completely reproduce exactly the same image with different formats and the same resolution 70%-95% of the time. IN film you had a smaller negative with associated limits to enlargement. In digital the DNG file will be the same size and enlargement possibilities will be the same.

An image taken with a 1 inch Panasonic FZ1000 taken at 100 ISO will be functionally the same as the same image taken with a 24 MP APS-c or 24 MP 35x24. The digital negative in many situations doesn't really care what format was used to capture the image. although people will argue until they are blue in the face against that.

There's still folks that are so locked into film thinking, they think you can enlarge a 12 MP 35x24image, more than you can enlarge a 24MP 1 inch sensor image. This kind of thinking is still being passed down from old film guys to guys who have only shot digital.


Last edited by normhead; 09-08-2016 at 05:32 AM.
09-08-2016, 05:27 AM - 1 Like   #9
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QuoteOriginally posted by normhead Quote
picking 36x24 to be called "full frame" disingenuous
'cause the 645s and Hasselblads are Fuller Frames and that is just silly.
09-08-2016, 05:32 AM   #10
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QuoteOriginally posted by normhead Quote
But go with the flow works for me. Look through the view finder, what do you see, want wider, get a wider lens, want longer, get a longer lens, or just forget the whole thing and get an 18-135.
Not on an *ist-series body, though. Nor on some of the early K-series digitals.

QuoteOriginally posted by normhead Quote
The whole idea of one sensor 36x24 being some kind of true sensor and anything smaller being a "crop" sensor is just complete photo enthusiast hogwash.
GIven that the DSLR evolved more or less directly from the 35mm film SLR camera, it is a useful and reasonable frame of reference (pun sort of intended); what is wrong is to regard "full frame" as being the Holy Grail or the Only Reasonable Option.

I think Pentax being full-frame-free for most of its digital history has kept us Pentaxians grounded and clear-thinking in this regard, at least within the bounds of our own camera ecosystem. Even with the arrival of our own production full-frame DSLR, we are calm and rational enough to analyse it from a rational viewpoint for what it is and its place (or otherwise) in our individual set of needs or wants. Setting aside those who didn't buy it because they simply can't afford it, those who COULD afford it and chose NOT to buy it were (as far as I am concerned) characterised by their logical and well-thought-out position on WHY they were not buying it, and those who could afford it and chose to do so weren't exactly lining up to stick the knife into people who shared their lack of financial limitations but still bought a K-3 series body in preference.

I would like that kind of sanity to continue prevailing here.
09-08-2016, 05:36 AM   #11
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QuoteOriginally posted by pathdoc Quote
I would like that kind of sanity to continue prevailing here.
Great thought (but in regard to sanity prevailing, you obviously haven't spent much time in the Why I won't buy a K3 thread.)
09-08-2016, 05:39 AM   #12
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QuoteOriginally posted by rod_grant Quote
Great thought (but in regard to sanity prevailing, you obviously haven't spent much time in the Why I won't buy a K3 thread.)
Sanity is way over-rated.

I mean honestly, be as sane as you want, but think about it.. "what's in it for you?".
09-08-2016, 05:40 AM   #13
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QuoteOriginally posted by pathdoc Quote
Not on an *ist-series body, though. Nor on some of the early K-series digitals.



GIven that the DSLR evolved more or less directly from the 35mm film SLR camera, it is a useful and reasonable frame of reference (pun sort of intended); what is wrong is to regard "full frame" as being the Holy Grail or the Only Reasonable Option.

I think Pentax being full-frame-free for most of its digital history has kept us Pentaxians grounded and clear-thinking in this regard, at least within the bounds of our own camera ecosystem. Even with the arrival of our own production full-frame DSLR, we are calm and rational enough to analyse it from a rational viewpoint for what it is and its place (or otherwise) in our individual set of needs or wants. Setting aside those who didn't buy it because they simply can't afford it, those who COULD afford it and chose NOT to buy it were (as far as I am concerned) characterised by their logical and well-thought-out position on WHY they were not buying it, and those who could afford it and chose to do so weren't exactly lining up to stick the knife into people who shared their lack of financial limitations but still bought a K-3 series body in preference.

I would like that kind of sanity to continue prevailing here.
you folks are throwing off the grading curve

bonus points to all
09-08-2016, 05:43 AM - 1 Like   #14
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Allen, the real answer is to enjoy the camera that you have got; you can't take a good photo with one you haven't got - you can't even take a bad one!
09-08-2016, 05:51 AM   #15
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QuoteOriginally posted by Aslyfox Quote
1 since I am using a dslr, either a K 3 or K 5 II, instead of a film camera there is a factor that is used to get the equivalent film size of the lens you are using, correct?
Yes

QuoteOriginally posted by Aslyfox Quote
2 What is it - 1.5, 1.25, 1.4, 1.75 ??? for my specific camera bodies?[
1.5

QuoteOriginally posted by Aslyfox Quote
3 You then multiple the factor times the focal length of the lens, so as an example, a 200 mm lens becomes a 300 mm lens? (200 x 1.5 = 300), is that correct
Yes, to get the equivalent focal length on small format film.

QuoteOriginally posted by Aslyfox Quote
In other words by using a dslr instead of an old film camera you have a built in teleconverter?
Yes, for your DSLRs. But, no, for other DSLRs. Not all DSLRs have a sensor smaller than small format film.
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