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04-28-2018, 12:29 AM   #1
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What does this mean - 35mm equivalent?

I have a Pentax k-50 body and various Pentax and Takumar Lenses. When viewing the EXIF Data, the focal length will say, 110mm, 35mm equivalent to 165mm. The K-50 is a 35mm body, so why show a difference?

Thanks for the help.

Tonytee

04-28-2018, 12:37 AM - 1 Like   #2
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The K-50 is an APS-C body so a crop factor of 1,5 compared to FF (35mm)

Last edited by Bengan; 04-28-2018 at 12:50 AM.
04-28-2018, 12:39 AM   #3
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QuoteOriginally posted by Tonytee Quote
I have a Pentax k-50 body and various Pentax and Takumar Lenses. When viewing the EXIF Data, the focal length will say, 110mm, 35mm equivalent to 165mm. The K-50 is a 35mm body, so why show a difference?

Thanks for the help.

Tonytee
Hi Tony

The K-50 isn't a 35mm body - it has a smaller APS-C sensor, which is cropped by a factor of 1.5x when compared to a 35mm or so-called "full frame" sensor. Because of this, if you fit a lens of 110mm focal length to it, the field of view captured by the smaller sensor will be equivalent to that from a 165mm (110mm x 1.5 crop factor) lens on a 35mm camera

Last edited by BigMackCam; 04-28-2018 at 12:50 AM.
04-28-2018, 12:41 AM   #4
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Tony tee
The k-50 is a aps-c sensor (25.1x16.7mm sensor), or cropped sensor, not a 35mm format otherwise referred to as full frame.

Being a bit smaller than full frame the cropped sensor is ‘upsized’ when reported in FF format. The crop factor is about 1.5x hence 110mm is equivalent to 165mm.

The K-1 is a genuine 35mm format

Does this make sense ?

04-28-2018, 06:29 AM   #5
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Because the 35mm film format was so dominant everybody became familar with how images looked using this film size ie what the field of view would be. Most digital cameras are made with sensors that are smaller than that film size however. The smaller the sensor the narrower the field of view is with a lens of a particular focal length. This doesn't matter: WYSIWYG! What you see is what you get! However many photographers are so used to 35mm that they find it helpful to still have that as a benchmark comparison, so we have this "crop factor" which gives us the 35mm field of view. So by way of example, 50mm is the standard lens on 35mm, giving a field of view similar to that by eye alone. With a pentax dslr, all except for K1 have an "apsc" sensor, the field of view with 50mm is less. It is the same as that given by focal length x the crop factor 1.5x = 75mm on 35mm film/full frame sensor.
Manufacturers also find it useful to inform the consumer what the range of focal lengths on a particular camera means using this yardstick.
04-28-2018, 09:05 AM   #6
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The EXIF data helps software figure out what to do with your image. Poorly written or really old software might only look at that one field, 35mm equivalent focal length, for focal length information. So Pentax puts something in that field, just to avoid incompatibility. It's not that hard to do when the image is created, way more annoying to add later. It may never get used.
04-28-2018, 05:03 PM   #7
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Yes, I see what everyone is saying. Basically, with the full frame camera, you record everything that is visible in the viewfinder. On a cropped sensor, I believe the variance is approximately 87% of what is in the viewfinder. Now my next question is: When shooting with let's say a K-1, is the IQ better than a non full frame camera?

Thanks, very much appreciated.

Tony
04-28-2018, 05:17 PM   #8
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QuoteOriginally posted by Tonytee Quote
Yes, I see what everyone is saying. Basically, with the full frame camera, you record everything that is visible in the viewfinder. On a cropped sensor, I believe the variance is approximately 87% of what is in the viewfinder. Now my next question is: When shooting with let's say a K-1, is the IQ better than a non full frame camera?

Thanks, very much appreciated.

Tony
On your K50, what you see in the viewfinder is what you are getting, it's "matched" per se to the sensor. If you put a "full frame" lens on the K50, the image circle it produces would be larger than the apsc sensor the K50 has, it would match the 24X36 sensor of the K-1 or a film camera. A DA lens is designed for the apsc sensor and produces an image circle to match it, but too small for a 35mm camera such as the K-1. But a 50mm lens is the same whether it's on a K50, K-1 or 645, they have just been designed to fit the sensor size of the camera they are used on.

Originally the designation, 50mm etc. was the distance from the element to the film plane, but with special optics, that requirement has changed.

IQ will determined by the sensor itself and the quality of the optics.

04-28-2018, 05:28 PM   #9
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QuoteOriginally posted by Tonytee Quote
Yes, I see what everyone is saying. Basically, with the full frame camera, you record everything that is visible in the viewfinder. On a cropped sensor, I believe the variance is approximately 87% of what is in the viewfinder. Now my next question is: When shooting with let's say a K-1, is the IQ better than a non full frame camera?

Thanks, very much appreciated.

Tony
That is a tricky question to answer. The general view is that the larger the sensor, the better the IQ. However, that assumes identical lenses, identical shooting conditions, etc. etc. If you are testing on a resolution chart, in general a FF sensor give better IQ than APS-C, and the sensor in a 645 will be better still. In real-life shooting, given let's say 50 images some taken with a FF sensor and others with an APS-C sensor, I doubt very much that ten photographers would score much better than random chance trying to identify which images were taken with which camera.

BTW: When I was a student in college (California) I had two photo-buddies. One used a Pentax similar to mine, but Chuck used a Leica M3. The local camera store sold Leica as well as other brands, and had that attitude, "well if you can't afford a Leica or do not care about quality, Pentax is OK for amateurs." The dealer had the snobbish "of course Leica is superior." We brought him a slide tray with chromes made by all three of us and challenged him to pick out the Leica images. He refused to try. But BTW: the M3 was a beautifully made camera, arguably the best rangefinder ever, and there is no doubt that the 50mm f2 Sumicron was an excellent lens, but by magazine tests, the Takumar 50mm was at least as good.
04-28-2018, 05:36 PM - 2 Likes   #10
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This is the perfect diagram to understand the difference between the sensors. The image circle would be a full frame lens. With the same focal length on each camera, the image doesn't change, only the part that is recorded by the camera as shown by the blue box for apsc and red box for full frame.

04-28-2018, 06:35 PM - 2 Likes   #11
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QuoteOriginally posted by Tonytee Quote
Yes, I see what everyone is saying. Basically, with the full frame camera, you record everything that is visible in the viewfinder. On a cropped sensor, I believe the variance is approximately 87% of what is in the viewfinder. Now my next question is: When shooting with let's say a K-1, is the IQ better than a non full frame camera?

Thanks, very much appreciated.

Tony

The viewfinder covers 95%+ of the frame no matter what camera you are using, but on the full frame it's a bigger viewfinder.

Now my next question is: When shooting with let's say a K-1, is the IQ better than a non full frame camera?

That depends totally on circumstances. My tests have run up to 3840 x 2160 (4k). Both the K-3 and K-1 oversample the image and there is essentially no difference between them.

There is a theoretical notion that at some level of print or display, the K-1 will be better. I have absolutely no idea where that might be. People have lots of ideas about it, but fact is, no one has really determined with what media and at what resolution a difference can be detected. But detection is only part of the issue, it comes down to which image does an unbiased observer prefer. In that case there is no testing I know of that says the K-1 is more desirable than an APS-c camera.

What is better is in cases that test the Dynamic range of the camera the K-1 will be better. That would be sunsets and sunrises, or even shooting in the midday sun with harsh shadows, the K-1 will be better.

For my wildlife images you can't tell which is which at normal viewing sizes.









Some K-3 and K-1 images. Is there a difference in IQ? Can you even tell which is which?

It is possible there are small differences, but is it enough to care about?

The whole thing about one being a crop of the other is nonsense. When the diagram above is shown, it makes it appear like ASP-c gives you less of the frame. It doesn't. You use a different focal length to achieve the same framing. What they should be showing you is the smaller lens you can use on APS-c to get the same framing.A 200mm ƒ2.8 APS-c lens is 300 mm 2.8 equivalent. My 200 2.8 is 1.5 pounds. My 300 2.8 is 6 pounds. One I can hand hold, one I Need a good tripod to have any hope at all.

With the FF, you trade marginal increases in IQ for major increases in weight. Which is worth it, if and only if, you need or desire the extra IQ. The only people I've heard claim the extra IQ will matter would be people shooting for 60" prints or larger. And I tend to have trouble believing those people actually exist. People claim to do prints that size, but I know what they cost, so unless they sell prints at that size I'm dubious/ People can say whatever they want on the internet, for many reasons other than it's the truth.. Most of us rarely use the capacity we get from APS_c. But that doesn't mean we don't want ti there, but mostly because we all believe sooner or later we are going to take that stunning image we can sell for $60,000 or more. And when we do, we want the best print quality we can afford.

But, 1. it's never going to happen,
and
2. You'll never know if the same image was taken with an smaller sensor type camera, wouldn't have also made you $60.000. The fact that so and so great professional photographer took this picture with a full frame, rarely means he couldn't have taken the same picture with a smaller format, and made just as much for it. People claim to know this stuff, by reading specs. As far as I know, no one has actually done the work to know at what size an FF gives better image quality.

Last edited by normhead; 04-29-2018 at 05:14 AM.
04-28-2018, 09:18 PM   #12
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Whether there will be any "better" result by using a full frame body vs APS-C depends on many variable factors, including the lenses used and which APS-C body we are talking about. Then there's the subject matter, the conditions faced, the focal length used for what purpose, the post processing, etc. etc.

In practical terms, the difference in field of view will often create a difference in what uses a lens is optimum for employing. For instance, a full-frame lens of 50mm f/1.4 will serve quite well for doing closeup portraitures on an APS-C body, but is less suited for this purpose when mounted on a FF body that it was originally designed for. On a FF body, this lens was intended to serve as a "normal" FOV lens, neither wide angle nor tele. Those looking for a lens suited for optimum use for portraitures on a FF body will usually be shopping in the 77- 85mm range, which even with f/1.8 will be much more expensive. That said, some will use a FF body for this purpose, parting with a lot of money, including a lens of 85mm f/1.4 in order to get a more blurred background and a certain "look". But then we are dealing with a specialty niche.

There are numerous reasons for one preference or the other.
04-29-2018, 05:22 AM   #13
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QuoteOriginally posted by mikesbike Quote

, a full-frame lens of 50mm f/1.4 will serve quite well for doing closeup portraitures on an APS-C body, but is less suited for this purpose when mounted on a FF body that it was originally designed for.

There are numerous reasons for one preference or the other.
The one image I've seen, an environmental portrait of young boy on his tricycle in near darkness using a 50 on FF and a 35 on APS_c, there was a clear difference. I don't know of any other focal length where using am APS_c camera and lens and the equivalent FF camera and lens, you could look at those images and say "this one is the APS_c and this one is the FF" By 50-70 or 30-20 that difference is gone.

It's moot for me because I prefer 70+mm on FF or 50mm+ on APS-c, so for the way I shoot, I don't really care. But if you're that guy, who prefers shooting with 50mm on FF, you might not like 35mm on APS-c. That's pretty small exception.

Last edited by normhead; 04-29-2018 at 06:52 AM.
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