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10-13-2013, 11:39 AM   #1
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Digital Virgin...

Now that I've got your attention.... I am in need of advice from experienced DSLR users when it comes to focal length, magnification and field of view. I know what these terms mean as I shot 35mm in my Spotmatic for three decades with my Super Takumar 28, 35, 50, 135 and 300mm lenses. So I have a "sense" of what I will see when I look through these full frame lenses. It appears that I have made some incorrect assumptions while studying the lens descriptions on the B&H website and have confused "35mm equivalents" with actual increased magnifications. I understand that the actual field of view of a full frame lens (like the Sigma 24-70) will be narrower on the APS-C camera but the product information indicates that it will be comparable to 38-112mm.... which is a little confusing. Now the problem is compounded when I look at the Pentax DA*16-50 which is designed for the APS-C sensor and the lens description indicates that it is comparable to a 24-70mm lens. Based on my years of looking through full frame lenses I felt that the best all around "walk around" lens would be the 24-70 mm range lens.... so I ordered the DA*16-50 lens.... I had been planning to get the Sigma 24-70 lens but the description says its like a 38-112mm lens... At this point I have NO idea what I'll see when I look through either of these lenses but the DA16-50 is on the way and now maybe I need to send it back....
Can any of you suggest any recommended reading on this topic of magnification? Thanks

10-13-2013, 11:48 AM - 1 Like   #2
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Crop factor - Wikipedia, the free encyclopedia

The 16-50 should do exactly what you want it to.

DSLR Magnification
10-13-2013, 11:59 AM   #3
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QuoteOriginally posted by boriscleto Quote
Crop factor - Wikipedia, the free encyclopedia

The 16-50 should do exactly what you want it to.

DSLR Magnification
Thanks for the references... So when using the 16-50 on the 50mm side I will get something "like" the effect of a 70mm "portrait" lens? Maybe another way to look at this would be comparing a 70mm APS-C designed lens and a full frame 70mm lens.. If I looked through both of them the magnification would be the same but the field of view on the cropped lens would be narrower?? This could be pretty strange to someone who used one or the other a lot and then switched...
10-13-2013, 12:04 PM   #4
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I have the 24-70 specifically because I prefer that range on APS-c rather than the 16-50, which I used to have. But I am probably in the minority. That extra 20mm reach is far more valuable to me than the 8mm I'm giving up on the other end. If I think I may need something wider, which is rare, I bring along the diminutive 15 Ltd. Never was very impressed with the several 17-70's available, plus they're slower.

10-13-2013, 12:26 PM   #5
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QuoteOriginally posted by woodywesty Quote
So when using the 16-50 on the 50mm side I will get something "like" the effect of a 70mm "portrait" lens?
The field of view will be the same.

But in terms of depth of field,
f/2.8 on the DA*16-50
will be like setting f/4 on the FF 70mm lens.

QuoteOriginally posted by woodywesty Quote
Maybe another way to look at this would be comparing a 70mm APS-C designed lens and a full frame 70mm lens.. If I looked through both of them the magnification would be the same but the field of view on the cropped lens would be narrower?
The image circle from the FF lens would be broader.
10-13-2013, 01:34 PM   #6
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QuoteOriginally posted by lytrytyr Quote
The field of view will be the same.

But in terms of depth of field,
f/2.8 on the DA*16-50
will be like setting f/4 on the FF 70mm lens.



The image circle from the FF lens would be broader.
That's very interesting about the depth of field... now how about the sense of compression of the image as there would be a slight difference between a prime 50 and a prime 70 lens....??

I may just have to go back to school..
10-13-2013, 01:43 PM   #7
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QuoteOriginally posted by DogLover Quote
I have the 24-70 specifically because I prefer that range on APS-c rather than the 16-50, which I used to have. But I am probably in the minority. That extra 20mm reach is far more valuable to me than the 8mm I'm giving up on the other end. If I think I may need something wider, which is rare, I bring along the diminutive 15 Ltd. Never was very impressed with the several 17-70's available, plus they're slower.
Those are my exact thoughts.... only wish there was a dealer closer than 6 hours so I could look through them.
10-13-2013, 02:09 PM   #8
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QuoteOriginally posted by woodywesty Quote
Those are my exact thoughts.... only wish there was a dealer closer than 6 hours so I could look through them.
You could always rent one and see if it suits your needs...

CameraLensRental.com - Your online source for lens rentals and camera rentals

10-13-2013, 02:16 PM   #9
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QuoteOriginally posted by boriscleto Quote
You could always rent one and see if it suits your needs...

CameraLensRental.com - Your online source for lens rentals and camera rentals
Yes.. but my K3 is on order and I probably won't see it before late November and my new DA16-50 is "in the mail" from B&H. I'm sure that I will be happy with it once I get to use it. How can I be too disappointed since it is my first ever zoom! When Pentax comes out with their new teleconvertor I can stick my old Super Tak 300 on it and see what I see. Then I'll have a better idea about what I need for a long lens. Thanks for the info...
10-13-2013, 02:21 PM   #10
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Since you're used to changing lenses anyway, I'd add the DA*50-135 to the DA*16-50. It's a much better portrait lens anyway. These two DA* lenses are probably the best zoom combination available on a DSLR (short of the premium $2000+ f/2.8 zooms on a full frame Canon or Nikon).
QuoteOriginally posted by woodywesty Quote
Super Takumar
The Super Takumars with an adapter should cover your other needs well. At some point later, if you really want to go wide, the DA15, Sigma 8-16, or DA10-17 fisheye make good additions.


BTW, nobody makes a "fantastic" ~16-50mm APS-C lens for any brand of DSLR, so don't expect too much of it. Apparently it's just too hard to design one. But the DA*16-50 is still very good. In contrast, the DA*50-135 actually could be classified as "fantastic" - it's very impressive.

Last edited by DSims; 10-13-2013 at 02:30 PM.
10-13-2013, 02:31 PM   #11
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QuoteOriginally posted by DSims Quote
Since you're used to changing lenses anyway, I'd add the DA*50-135 to the DA*16-50. It's a much better portrait lens anyway. These two DA* lenses are probably the best zoom combination available on a DSLR (short of the premium $2000+ f/2.8 zooms on a full frame Canon or Nikon).

The Super Takumars with an adapter should cover your other needs well. At some point later, if you really want to go wide, the DA15, Sigma 8-16, or DA10-17 fisheye make good additions.
I agree... I've read sooo many positive reviews about the DA50-135. It's on my list when the funds become available. And I'm really excited about playing with my old Super Takumar lenses. I've bought two of the good Pentax thread to K adapters just for that purpose.... AND.... I can just keep shooting pictures, reviewing them, dumping the bad ones and not have to put new rolls of film in!
10-13-2013, 10:44 PM   #12
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QuoteOriginally posted by woodywesty Quote
I agree... I've read sooo many positive reviews about the DA50-135. It's on my list when the funds become available. And I'm really excited about playing with my old Super Takumar lenses. I've bought two of the good Pentax thread to K adapters just for that purpose.... AND.... I can just keep shooting pictures, reviewing them, dumping the bad ones and not have to put new rolls of film in!
Sounds good - enjoy your K-3! I'm a bit jealous, but I'll probably have to wait a while this time around, since the K-5 IIs I pre-ordered around this time last year is still meeting my needs pretty well.
10-14-2013, 10:03 AM   #13
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QuoteOriginally posted by lytrytyr Quote
The field of view will be the same.

But in terms of depth of field,
f/2.8 on the DA*16-50
will be like setting f/4 on the FF 70mm lens.
No, it won't. The DOF will be exactly the same as what you use. If you're at 50mm and f/2.8, then you get the same DOF whether you're on APS-C or 35mm.

Perhaps what you were trying to refer to is that when you use the same focal length lens on APS vs. FF, you need to stand closer to get the same framing using FF, which leads to shallow DOF.

The lens projects the same exact image no matter what medium you put behind it.
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