photo math

[Nathan Wernette]

OK. so there is some math that I don't understand or haven't found the right way to figure it out.

With an apsc size sensor, it has a crop factor of 1.5?

SO what is the 35mm equivalent if you put a 50mm lens on the camera.

Or better question, what is the math equation so I can figure it out myself.

thanks.

[Ian]

APS-C is basically 1.5 so a 50mm lens is 75mm on a full frame 35mm body.

http://en.wikipedia.org/wiki/APS-C

[Bob Gross]

It depends.

Some APS-C sensors are the size to produce a crop factor of 1.5. Others will yield 1.6. It depends somewhat on the brand.

If you put a 50mm lens on a 1.5 factor sensor, it will yield 75mm equivalent.

Note that it really doesn't give you 75mm, but it just appears as though it does.

–B.G.–

[Nathan Wernette]

so you half the original mm and add it back to it.

so a 30mm on a 1.5 is 45mm.

does all this really matter?

I have a 50mm minolta for my nex6 its like a 75mm on a full frame camera?

Bob you said it appears as it does?

Do all these really matter? besides having a wide angle lens like a 19mm sigma for my NEX. are all of these just general measurements.

I mean sure you'd have to get comfortable on judging how closer you are to a subject of a 50mm lens. but some make 50mm,55mm,58mm lenses. does it really matter?

[Bob Gross]

"Bob you said it appears as it does?"

Yes, it appears that way, because the image fills up the frame like 75mm would on a full frame sensor. However, it doesn't really give you the magnification that 75mm would.

If you are a wide angle panorama shooter, then a crop factor body "hurts you" because the crop factor makes the lens appear to be 1.5 or 1.6 times longer than on a full frame sensor. The crop factor makes your great wide lens act like it is a not-so-great wide lens. So, crop factor bodies are not very popular with the panorama people.

If you are a wildlife shooter, then a crop factor body "helps you" because the crop factor lets the lens fill the frame like a longer lens. Wildlife shooters almost never have a long enough lens for what they are trying to do.

"Do all these really matter?"

That is a rhetorical question for which there is no answer.

Most of what I do is with wildlife, so the crop factor acts like it helps me. I own no full frame cameras.

–B.G.–

[Doug Smith]

Tough to top what Bob said, he gave excellent info and examples.

I only just recently learned that some APS-C sensors were a crop factor of 1.5. I'd always heard of them as being 1.6 crop factor, and that's how I still think of them. Maybe brand does have something to do with it.

I really prefer to think in "full frame" terms. My last two cameras have been full frame, and I really can't see going back to a crop body. But like Bob said, that's just the style of photos I like to take. My sister uses a crop body (Canon 7D), and it's perfect for her. She loves wildlife and moving subjects, and her 70-200mm lens really gives her a lot of bang for the buck on a crop body.

Funny enough, I absolutely loved the exact same lens on my full frame because on a 35mm equivalent, 70-200 is a really nice and useful range. In fact it was my primary walk around lens.

I'm by no means an expert, just an enthusiast, but I'm currently at the point in my photography where I let the lens quality dictate my purchasing choice, not the focal length. I want the best glass I can afford in my price range, and I'll work around any limitations in focal length. This is also the reason I'm switching to primes (although truth be told, the 70-200 f/4 L IS is a phenomenal zoom).

One bonus to consider about full frame sensors, especially on the newer cameras, is they often remove the need for a zoom. The resolution is so incredible, even at 100% crop, that you can get very usable photos simply by cropping a wide angle shot.

This is just an example…although these are obviously two different photos, they were taken from the exact same distance, and show you just what kind of cropping you can do with a full frame:

…See, who needs a zoom lens? Hahaha ;-)

[Nathan Wernette]

It's not only a 1.5 crop factor it changes the aperture also right?

So a 50mm f2 acts like a 75mm f???

Right?

The sony apsc has a crop factor of 1.53.

A micro 4/3 specifically the omd em10 has a crop factor of 2

[Bob Gross]

"It's not only a 1.5 crop factor it changes the aperture also right?"

I detect the use of a pronoun without an antecedent.

–B.G.–

[Bob Gross]

Q: What is the focal length of a 50mm f2 lens when it is placed on a 1.5 crop factor body?

A: It is still 50mm. Nothing changed.

Q: What is the maximum aperture on a 50mm f2 lens when it is placed on a 1.5 crop factor body?

A: It is still f2. Nothing changed.

The maximum aperture of a lens shows the size relationship of the focal length and the lens diameter.

I have a lens where the front looks like a dinner plate, but it is only f8.

–B.G.–

[Doug Smith]

"It's not only a 1.5 crop factor it changes the aperture also right?

So a 50mm f2 acts like a 75mm f???

Right?"

You got me…I would have answered that question "f/2".

Someone with more knowledge than me will have to clarify that for you. I wasn't aware of an aperture change. Of course, a 50mm at f/2 will have a different DoF than a 75mm at f/2, so in that sense I guess you're right.

[Ian]

I follow Tony on YouTube and think he's a great source of information on stuff like this.

http://petapixel.com/2014/03/28/concise-explanation-crop-factor-affects-focal-length-aperture/

[Will Webster]

A 50mm lens on a body with a 1.5 crop factor has the same field of view as a (50 x 1.5 = 75) mm lens would on a full frame body.

An f/2 lens has the same light gathering ability regardless of the crop factor of the body it's mounted on – it's always f/2.

BUT depth of field is trickier. A 50mm f/2 lens on a 1.5 crop body has approximately the depth of field of a 75mm f/3 lens (2×1.5). Depending on your useage this may be a good or a bad thing.

[Nathan Wernette]

ok, sorry for my poor use of the english language there. It was 2:00am in the morning and avoidance behavior was in effect, typing from my iPad in bed.

Today is the first day of school (teacher here) and I was avoiding going to bed!

I think i'm just getting wrapped up in numbers.. but now have a better understanding of crop factor and such.

[Author]

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