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01-02-2013, 02:29 PM - 1 Like   #1
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35mm equivilant

I've read about this and even talked with a few people, but let me ask in simple terms so that I'm sure I get it. Sorry for the complete newbee question, but thanks for inviting me to ask it here.

I shot a roll of film this weekend on a 35mm SLR that I've had since the 80s using a 75-200mm zoom. If I had been using a modern Pentax (for example) DSLR like the K-30 or K-5 would the 50-200mm or the 28-135mm zooms have been most consistent on the outer reaches of telephoto?

Like wise, when I buy a lens for the K-5 ii that I hope to own soon to function as my fast 50mm film lens does, should I be looking at 50mm lenses or 35ish mm lenses?

Granted there is a lot more to consider in choosing lenses, but I'm just trying to make sure that I understand this one aspect for now. Thanks in advance for your answers. I hate asking what I know to be idiot questions, but it's better than not learning and since there are no Pentax dealers in my state and I'm convinced that I'm going to buy a Pentax, I'm trying not to ask them at my local, very helpful shop that would like to talk me into another brand.

01-02-2013, 02:39 PM   #2
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A 50mm lens is a 50mm lens and a 35mm lens is a 35mm lens no matter what camera you are using them on.

The only thing that changes is the field of view.

Crop factor - Wikipedia, the free encyclopedia

So if you want a portrait lens on APS-C, get a 50mm. If you want a normal lens get a 28 or 35mm. Or just use the 50mm for both and take a step or two back.
01-02-2013, 02:54 PM   #3
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Thank you for the quick and patient reply. So, magnification doesn't change, but because the surface area capturing the image is smaller, the image is cropped more tightly?

That actually makes a lot more sense. Something about the way people look at me, tilt their heads and say "well, 35mm equivalent..." made me wonder if I was missing something important.

In music there are "concert tuned" instruments and "transposed instruments", which means that horn players play the same notes as (for example) a piano player, but they pretend that they are actually different notes to make them sit better on a piece of orchestral sheet music. So, they're constantly saying things like "concert Bb or my Bb?" Makes me want to....well let's just say that I'm glad that this isn't like that.

Thank you again for your response and the link.
01-02-2013, 02:58 PM   #4
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boriscleto covered it well.

The only people who should have a problem with crop-factors are those going back and forth between digital and film or those just transitioning to digital. I have not shot film in so long that 1.5 crop looks 'normal' to me. It is just a field of view thing, and if you are used to selecting primes based on what you want a shot to look like then you will need to re-train a bit.

A 28-135 will LOOK like a 42-200mm zoom but I think you meant the 18-135 which will look like a 28-200mm but it is still an 18-135mm as far SR and actual focal length is concerned.

01-02-2013, 02:58 PM   #5
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Yep, basically the lens is the same, just the "film" is smaller, which makes the frame seem as if you were using a longer focal length. But on the other hand, a lot of lenses have poor edge performance and vignetting, so this avoids all of that. I'm not quite sure what range you want, but the good thing with Pentax cameras is that all Pentax lenses will work on it (manual focus lenses will, of course, stay manual). Feel free to check out the Lens reviews database on this forum for individual lenses, see if you can find something that strikes your fancy
01-02-2013, 03:28 PM   #6
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Thanks, guys. This is not going to be a big deal to me. I would love to say that I'm such an experienced film photog that this will trip me up, but I'm not and based on what you've helped me understand, it wont.

A few things really draw me to Pentax and one is the playground of available lenses from decades past and present. Lots of things on my local craigslist, so I've been spending a lot of time in that lens review db, thanks for those of you who have contributed to that.

But, I need a body first. Might pick up a used placeholder body and focus on lenses, but I'm going to try to wait out the price on the K-5 ii and see what happens.
01-02-2013, 03:32 PM   #7
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The answers here are correct, but I think angle of view is more important to understand. When I put a 50mm lens on my K-5 I can't get the same perspective as I can with a 50 on a 35mm film Pentax. I can back off a few steps to get the subject the same proportion in the frame, but it still has a different perspective because it doesn't cover the same angle of view. If I enlarge the resulting pictures from the K-5 and 35mm film so the subjects are the same size, the backgrounds look different because of the angle of view.
In general a 35 mm lens on the K-5 (like the nice DA 35 2.4) gives equivalent working distance and perspective to a 50 mm lens on 35 mm film. There is still a difference in depth-of-field at the same f-stop, but that isn't a concern on most pictures.
So, yes: a 50 mm lens is always a 50 mm lens, but it only gives a "normal" perspective on a 24x36 film or sensor frame. On my Pentax 6x7 it would be quite a wide angle, and on a K-5 it would be a short tele (portrait) narrow angle lens.
01-02-2013, 03:46 PM   #8
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Thanks for the additional information, Tom. I'm just getting back into this and I'm not that used to a "normal" that I think this will trip me up yet. I need to settle into a new camera and the enjoy getting to know a few lenses of varying focal lengths with it. Looking forward to it.

01-02-2013, 04:15 PM - 1 Like   #9
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QuoteOriginally posted by troika Quote
...But, I need a body first. Might pick up a used placeholder body and focus on lenses, but I'm going to try to wait out the price on the K-5 ii and see what happens.
My experience is that the price slowly falls from "way more than I'd pay" to "still more but I've been waiting forever", then you buy. Then the price plummets about a month after you get your camera.
01-02-2013, 04:24 PM   #10
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So, I've got that to look forward to.

I know that this is the highest they'll ever be. I usually buy outgoing models, but I think the autofocus upgrade on the K-5 for me, sounds significant enough that I should spend the extra money on it. I think the K-30 is an amazing buy, but it doesn't really speak to me. If I happen upon a K-5, K-30 or even K-7 used at the right price with some good kit, I might pick it up and still aspire to a K-5 ii body, but have more time to wait out the price (and get some more reviews from field tests). Most likely, when someone has a sale, I happen upon a coupon or the price drops as it seems to have x months in with other Pentax models, I'll pounce.

In the mean time, I'm studying photography through books, on-line and by trying not to over impose on a very helpful friend who is a commercial photographer locally and shooting film and compact digital out of auto mode.

The best local camera shop sells Canon, Nikon and Sony and if you buy one from them, they throw in a 2 hour class on the camera you bought. Big incentive, I wouldn't be considering Pentax if it weren't for the Pentax Forums and the idea that I can get at least some of that information here. I promise to do my own work and not wear out my welcome with mundane Noob questions here either.

Thanks guys. Now, if one of you could just over-night me a big pile of money, we'd be set.

Last edited by troika; 01-02-2013 at 04:33 PM.
01-02-2013, 05:10 PM   #11
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Like boriscleto said, your image will be cropped "by default", so a 50mm will give the field of view of a portrait lens, a 35mm of a normal, etc.

Note, though, that it will be impossible to find a, e.g., 35mm with a large aperture like f/1.4, so it's harder to get the same depth of field (bokeh) you get on film for the same field of view. So you need to choose between depth of field and field of view (or money for very fast lenses).
01-02-2013, 08:45 PM   #12
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Obrigado.
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