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03-17-2014, 08:47 AM   #1
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Lens length in articles

I always wondered this, and I know it will sound like a very noobish question.

This blog posted the article on 15 reasons to love a 35mm. My question: Do they mean a 35 mm on a full frame, aka a 22-24 mm for a 1.5 crop?

or

Are they saying a 35mm lens made for cropped? Like sigma makes then for aps-c sensors, does that fall in the same category? Or are they really saying, translated for a k-5iis owner, 15 reasons to love your 24mm lens.

Sorry this is a simple thing but it confuses the hell out of me.

03-17-2014, 08:54 AM   #2
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Which blog?
03-17-2014, 09:01 AM - 1 Like   #3
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QuoteOriginally posted by rzarector Quote
Or are they really saying, translated for a k-5iis owner, 15 reasons to love your 24mm lens.
This blog : 15 Reasons to Love Your 35mm Lens - The Phoblographer ? From what they're saying, "They’re the Perfect Balance Between Wide and Normal", "35mm is the Most Bokehlicious of the Wide Angles" and the picture at the top of what appears to be a full frame 5d, I'd say they're referring to use on a full frame camera. So, it translates to 10 reasons to love your 24mm, after the crop factor is accounted for.
03-17-2014, 09:02 AM   #4
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In a strict sense, the focal length of a lens, means the focal length of the lens regardless of format.

03-17-2014, 09:07 AM   #5
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Back in the full frame days, there were the 50mm and 35mm lenses that were the "go to" lenses. 35mm was considered wide angle and 50mm was considered normal. These focal lengths were relatively easy to design, so they gave good photo results (good image quality) at a relatively low price. Due to the film size and focal length, they also produced fairly natural looking photos, without odd distortions or optical problems.
On APSC you loose some field of view. The lens is just as good as it was before, though. So a 35mm lens is still great and gives you a lot of bang per buck, but its not a wide angle lens anymore.
Same for 50mm. Pretty cheap, great IQ, good brightness (fast aperture), but its not really "normal" in terms of field of view, so its not as versatile as it was on FF.
So the blog is probably talking about film/full frame.

But keep in mind that 35mm made for FF or 35mm made for crop will look the same on your camera! The focal length (measured in mm, independent of camera) is not the same as field of view (measured in degrees, after the photo is taken)! You see, the focal length is a lens property, but the field of view can be affected by the medium (the film, sensor size). On crop cameras it is cropped. Hence the name. So any 35mm lens from any manufacturer will look the same on your Pentax DSLR.

It only becomes problematic if you use a "crop" lens on a full frame, because the lens might have poor edge performance or even completely black edges (vignetting). This is because the lens makers expect that there is no film/sensor to record those edges. But! Many "crop" lenses work just fine on full frame. I think there is a thread about these on the forum somewhere. You see, calling a lens "FF" or "crop" has become a bit of a marketing buzz word.

In short, the Pentax DA 35mm f2.4, DA 35mm f2.8 macro ltd, FA 35mm f2.0, DA 50mm f1.8, DFA 50mm f2.8 macro, and FA 50mm f1.4 are all great lenses (and all are available as new). The regular DA ones are also pretty cheap. For under $500 you can buy both the DA 35mm f2.4 and DA 50mm f1.8 and you have a great kit! Very sharp lenses, good low light performance, fast AF, very compact and light, great for beginners, but they also allow you to develop your art

If you want some sample photos of the great DA 35mm f2.4, check this thread:
https://www.pentaxforums.com/forums/122-lens-clubs/196639-da35-f2-4-plastic-fantastic-club.html

If you want some really, really in-depth reviews of the various Pentax 35mm lenses, check this thread (its old, so don't post in it, but it has sample photos):
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/118765-da-3...ny-photos.html

Last edited by Na Horuk; 03-17-2014 at 09:15 AM.
03-17-2014, 09:08 AM   #6
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Well, it's on an EOS so that's a crop sensor. This makes it roughly equivalent to a 50mm on a FF camera, which was a "normal" lens.

Personally on my K5 I like my Sigma 28mm f1.8, it really just gives the "eye view" images I like. I know that's what he's trying to say - it's kind of a documentary view of photography.
03-17-2014, 09:10 AM   #7
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35mm is 35mm no matter the format of your camera...
03-17-2014, 09:18 AM   #8
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I'm working my way wider.

One theory is that a normal lens is that the focal length equals the diagonal of the sensor area.

FF 24x36= 43.26
APS-C 23.7 × 15.7 mm CMOS sensor = 28.42

Guess what my next lens is. FA 28mm

03-17-2014, 09:18 AM   #9
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QuoteOriginally posted by BrianR Quote
This blog : 15 Reasons to Love Your 35mm Lens - The Phoblographer ? From what they're saying, "They’re the Perfect Balance Between Wide and Normal", "35mm is the Most Bokehlicious of the Wide Angles" and the picture at the top of what appears to be a full frame 5d, I'd say they're referring to use on a full frame camera. So, it translates to 10 reasons to love your 24mm, after the crop factor is accounted for.
That is it.

Still really confused.

I get the idea that a 35mm lens is still the same, but when you read posts like this, which are all over, My 35 is the best walk around yada yada, If I go buy the pentax 35mm 2.8 and mount it on my k5iis, the image crop will take away more from my frame than the nikon guy with his FF camera. As far as surface area of what could be captured with that lens if I was using a film camera.

but then say I buy the sigma, says in specs, made for aps-c. If you use this on a ff it will look really odd and you'd have to crop a lot of it. But if you take that made for aps-c 35, and put it on a aps-c, are you now getting the full range of a 35mm as if it was on a film lens image wise? or you still have a crop to have it not gather all the 35mm a film would at the same time and place?
03-17-2014, 09:25 AM   #10
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35mm... on a FF camera IS 35mm...
35mm... on a crop camera is still a 35mm but by adding the crop factor it becomes more of a 50mm...

So, I'm not quite sure how a 35mm becomes a 24mm on a FF body ... !?!?!?!?!?
03-17-2014, 09:29 AM   #11
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mrNewt: 35 on FF is like 24mm on our crop sensor Pentax.
03-17-2014, 09:29 AM   #12
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QuoteOriginally posted by mrNewt Quote
So, I'm not quite sure how a 35mm becomes a 24m on a FF body ... !?!?!?!?!?
Two cameras side by side. 1 is FF 1 is aps-c.

Crop camera has on a 24 2.8 (FF lens)
FF camera has on a 35 2.8 (FF lens)

Question 1: The images captured would be almost identical?

But if you take a lens made for apsc. LIke my sigma 17-50 says its made for aps-c so using on a FF would not really be ideal.

Crop cam 35mm 2.8 (crop lens)
FF cam 35 2.8 (FF lens)

Question 2: Do those equal out to identical shots?
03-17-2014, 09:30 AM - 1 Like   #13
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QuoteOriginally posted by rzarector Quote
but then say I buy the sigma, says in specs, made for aps-c. If you use this on a ff it will look really odd and you'd have to crop a lot of it. But if you take that made for aps-c 35, and put it on a aps-c, are you now getting the full range of a 35mm as if it was on a film lens image wise? or you still have a crop to have it not gather all the 35mm a film would at the same time and place?
It doesn't matter if the 35mm was made for aps-c or if it was an old film-era 35mm, they'll both give the same field of view on your k5iis. That's the '35mm is 35mm' mantra.

The points in the article that are referring to the field of view, like a 35mm being good for full body portraits in tight spots, these would apply a wider angle lens on aps-c, something in a 24mm range. (I'm still operating under the belief that the article is referring to use on a full frame camera)

Get your hands on a k1000 and cheap film-era 50mm. Swap lenses back and forth with your k5ii. This is an easy hands on way to compare what the 'crop factor' does.
03-17-2014, 09:34 AM   #14
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QuoteOriginally posted by rzarector Quote
Two cameras side by side. 1 is FF 1 is aps-c.

Crop camera has on a 24 2.8 (FF lens)
FF camera has on a 35 2.8 (FF lens)

The images captured would be almost identical.

But if you take a lens made for apsc. LIke my sigma 17-50 says its made for aps-c so using on a FF would not really be ideal.

Crop cam 35mm 2.8 (crop lens)
FF cam 35 2.8 (FF lens)

So those equal out to identical shots?
Oh... sorry I guess I miss-read it.
Yes, in that case I would say it is true...

24mm on a crop will give similar results as a 35mm on FF...
35mm on a crop camera will give you similar results as a 50mm on FF...

As for Sigma's statement of lens done for APS-C format only is baloney a little bit.
The only issue you will find on that lens is that at 17mm, on FF you will have a "tunnel" vision .
03-17-2014, 10:20 AM - 1 Like   #15
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QuoteOriginally posted by rzarector Quote
Two cameras side by side. 1 is FF 1 is aps-c.

Crop camera has on a 24 2.8 (FF lens)
FF camera has on a 35 2.8 (FF lens)

Question 1: The images captured would be almost identical?

But if you take a lens made for apsc. LIke my sigma 17-50 says its made for aps-c so using on a FF would not really be ideal.

Crop cam 35mm 2.8 (crop lens)
FF cam 35 2.8 (FF lens)

Question 2: Do those equal out to identical shots?
you're getting yourself confused by overthinking and integrating too many things into a single question.

think chocolate ship cookie dough and cookie cutters. you have a big circle of cookie dough (image circle) - you have 2 cookie cutters (one big rectangle + 1 small rectangle)
if you make a big rectangle cookie, you get more chocolate chips because you have taken more of the cookie dough. if you use the small cookie cutter, you get less chocolate chips because you've made a smaller cookie.

they are both chocolate chip cookies, one is just bigger than the other.

your sensor is the cookie cutter, the cookie dough represents the image circle projected by the lens.
that's the only difference until you start talking equivalency which is a matter of field of view.

so when you ask the question, why do I love my 35mm lens, you have to ask the RIGHT question:

Do I love my 35mm because of its IQ?
Do I love my 35mm because of it's field of view?
Do I love my 35mm because of it's compactness?
Do I love my 35mm because of it's value?
Do I love my 35mm because of its maximum aperture (shall depth of field capabilities)?

Once you answer one or all of those questions, then you can figure out what lens for what sensor size you want to love.
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