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03-10-2012, 04:09 AM   #361
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With all this talk of FOV/DOF equivalencies, I just thought of an interesting illustrative example of the differences between FF and APS-C that Pentax users can appreciate:

See those crazy 50 f/1.2 photos in the f/1.2 club? Well, 1.54x crop of 50 f/1.2 gives an equivalent of 77mm f/1.8 if I'm not mistaken. So that's pretty much exactly identical (FOV/DOF-wise) to what the FA 77 ltd looks like on FF (a remarkable coincidence I should mention), only you get AF, and (in my opinion) better IQ in a slightly smaller/lighter package, not to mention being much easier to acquire.


Last edited by Cannikin; 03-10-2012 at 04:28 AM.
03-10-2012, 04:36 AM   #362
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QuoteOriginally posted by Cannikin Quote
With all this talk of FOV/DOF equivalencies, I just thought of an interesting illustrative example of the differences between FF and APS-C that Pentax users can appreciate:

See those crazy 50 f/1.2 photos in the f/1.2 club? Well, 1.54x crop of 50 f/1.2 gives an equivalent of 77mm f/1.8 if I'm not mistaken. So that's pretty much exactly identical (FOV/DOF-wise) to what the FA 77 ltd looks like on FF (a remarkable coincidence I should mention), only you get AF, and (in my opinion) better IQ in a slightly smaller/lighter package, not to mention being much easier to acquire.
To be used on a camera that, if existing, would cost at the least tree times an APS-C of equivalent specs.
03-10-2012, 05:34 AM   #363
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Some thoughts about DoF, wide angle and crops

QuoteOriginally posted by Aristophanes Quote
Show. Don't tell. Post photos with EXIF to demonstrate. Enough talk.
My dear friend. First comes the experiments (photos), then comes the theory (understanding). We already reached this point, we understand.

-> Falk Lumo: Camera equivalence

So, to debate your issue (and I don't totally disagree with your point of view), you'll have to discuss it in equivalence terms:

A 35mm/1.4 lens for APSC doesn't exist (it would be a 23mm/0.9). The closest thing for APS-C would be 24mm/1.4 (as exists for Nikon) which we can use on APSC too of course. Translating back to FF this means the following statement is true:
APSC forces you to shoot with a 36mm/2.1 equivalent lens rather than a 35/1.4.
Now, we have translated the discussion into known territory, no need to speculate.

Some (as yourself) would say that the difference between a 36/2.1 and a 35/1.4 isn't visible or of no interest. Fair enough and many may share your point of view.

Others though will say that it matters absolutely. It's the only explaination for f/1.2 lenses which have been made and costed a fortune. YMMV

Put please, discuss this in an educated style w/o listing tables of DoF values. It is ridiculous. We do understand this stuff, don't we?


P.S.
One may argue that DoF is no topic with wide angle. However, this is not true. The defocus blur (characterized by the corresponding circle of confusion diameter coc) simply is:
coc_df = M^2/N depth
where M is the magnification, N the lens aperture FStop and depth (if small compared to the focus distance) is the distance in the real space from the plane in focus (or half the DoF).

And as you can see, the focal length is missing. Defocus blur does only depend on magnification and FStop. And magnification (e.g., for a 36cm face onto 36mm portrait or 1:10 which means 35cm distance with a 35mm lens!) is constant for a given subject, only the perpective is changing. As you can see too, depth decreases with M^2! So, even if the relative depth is kept constant (the subject becomes smaller overall), you still have to keep N propoprtional to 1/M. I.e., larger subjects can be shot with larger apertures w/o the "razor-thin DoF" issue. So, a general argument saying that a large aperture equals a razor-thin DoF is typically from people who simply don't understand.

BTW, this does not hold true for background blur (large depth). The background blur is
coc_bg = M f/N = M d
where f is the focal length (f/N is the physical lens aperture diameter d). So, while defocus blur does not depend on the focal length, subject isolation from the background does. This is another common source of confusion.
coc_bg / coc_df = 1/M f/depth
So, f >> M*depth is required to isolate a subject with a given depth against a background without risking to blur the subject itself. In the face example above (M=0.1 and depth = 35cm/2) we get f >> 17mm. Of course, the entire discussion is based on 35mm equivalent figures. Translate as required. Note that magnification M depends on the crop factor c, M = M' / c.

Last edited by falconeye; 03-10-2012 at 07:08 AM.
03-10-2012, 07:28 AM   #364
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QuoteOriginally posted by RXrenesis8 Quote
Clicking each photo navigates to the EXIF info page.

Vina | Flickr - Photo Sharing!
Wonderful photograph of a wonderful girl.

03-10-2012, 08:59 AM   #365
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QuoteOriginally posted by falconeye Quote
Wonderful photograph of a wonderful girl.
Wish I could take credit but these are not my photos, please share your comment with the photographer!
03-10-2012, 09:06 AM - 1 Like   #366
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Equivalency! (the Musical)

QuoteOriginally posted by Aristophanes Quote
You don't NEED the f/0.85 because, quite frankly, most photos the difference is not noticeable. I've tried with prints and it is bloody hard to see.

.
You wouldn't need 55 f/0.85, you would need 35 (really 36) f/0.85 to get an equivalent image on aps-c!

And if you crop the 55mm shot on FF to get the same FOV as the 55 gives you on aps-c, shot from the same position, your DOF should be basically the same - as stated in various equivalency articles, including Bob Atkin's point #3 :

If you use the same lens on a APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL

Which would explain why you were having a problem seeing the difference in your tests!


.
03-10-2012, 09:09 AM   #367
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QuoteOriginally posted by RXrenesis8 Quote
Wish I could take credit but these are not my photos, please share your comment with the photographer!
You shouldn't quote photos without paying proper credit. How shall I know that you aren't kmayer on flickr? I'm not using flickr anyway.
03-10-2012, 09:15 AM   #368
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QuoteOriginally posted by RXrenesis8 Quote
I'll let you guess which one is the FF 50 1.4 and which is the APS-C 35 1.4.
I thought this was going to be a trick, because it was easy to tell the difference.

03-10-2012, 11:05 AM   #369
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QuoteOriginally posted by falconeye Quote
You shouldn't quote photos without paying proper credit
What, in your opinion, is "proper credit"?
03-10-2012, 12:06 PM   #370
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[deleted]

Last edited by beholder3; 08-11-2013 at 07:38 AM. Reason: [deleted]
03-10-2012, 01:26 PM   #371
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QuoteOriginally posted by beholder3 Quote
I guess falconeye is reffering to the legal situation in some countries. Here it is a clear copyright infringement to directly show (rather than just giving a hyperlink) somebody else's picture and can be very costly.
You sure it works like that, both are links though and he isn't claiming the photos are his.

I see it a bit like this with linking.
placing and showing the photo directly - i open a book with the photo and show you the photo
hyperlink - i give you the book and say on which page the photo is
03-10-2012, 02:03 PM   #372
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QuoteOriginally posted by RXrenesis8 Quote
Clicking each photo navigates to the EXIF info page.



Vina | Flickr - Photo Sharing!



Election in Luxembourg | Flickr - Photo Sharing!

I'll let you guess which one is the FF 50 1.4 and which is the APS-C 35 1.4.
Top photo is really nice!!!!!!!
03-10-2012, 02:56 PM   #373
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QuoteOriginally posted by stanleyk Quote
Top photo is really nice!!!!!!!
Must be that FF DOF!!!!
03-10-2012, 03:34 PM   #374
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Last edited by beholder3; 08-11-2013 at 07:00 AM. Reason: [deleted]
03-10-2012, 04:47 PM   #375
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QuoteOriginally posted by beholder3 Quote
Your not going anywhere here when you actually descend from ivory tower down to real pictures.
Don't start to compare, because you can only "prove" any differences when sticking to aspects few average onlookers will ever notice.
Take that unsharp dog again:
http://www.darrenleow.com/img/s11/v33/p21853329-5.jpg

Then look at APSC and el cheapo (average 120 EUR used) Porst lens (taken from the F1.2 lens club thread):
http://farm8.staticflickr.com/7151/6447095941_13e23d53da_b.jpg

What a whopping difference.

I have the Cosina 55 f/1.2, and it's one of the funnest lenses I'e ever owned - but it's actually quite soft wide-open:




...it's tough to focus accurately, and and 55mm feels pretty long (to me) for indoor or close-quarters shooting.

A 50mm on FF gives me the perfect angle of view, and with FF, a bit more of DOF control if I want to use it. The angle of view is the main reason I think I shoot a 50mm on FF - it's just a small, sharp combo that's incredibly useful and fast-focusing. The DOF is kind of a bonus.

Most of my 50mm shooting is between f/2 and f/4 - where I can enjoy a good dose of sharpness on the plane of focus, good contrast, and a bit less CA while keeping the shallower DOF. My 35 f/1.8 (and FA f/2 before it) is pretty good wide-open, but not quite the same as a 50mm at f/2.8, for example.

The following is 50mm at f/2.8 on FF, no PP, and is about the equivalent of about a 33mm f/1.8 would be on aps-c - now, I'm obviously not trying for 'razor thin DOF' here, just trying for f/2.8 sharpness and contrast while retaining some nice 'subject float', an attempt to keep the attention on the plane of focus, maybe create some 'pop' - look closely at the sharpness, the contrast and color. It's just hard for me to get that wide-open with a 35mm lens I've tried on aps-c, even the 31ltd (maybe a Zeiss?)



(that's a $110 lens on FF)


These kinds of things are subtle - I'll admit that fully - but you really, really do start to notice it if you shoot a lot. You start to develop a taste and a preference.

Yes, I also like the 'look' of a fully-wide-open 50mm shot on FF, but It's not always about that:

50mm f/2 (33mm f/1.2 aps-c equiv)

50mm f/2.2 (33mm f/1.4)

50mm f/2.2 (33mm f/1.4)

50mm f/2 (33mm f/1.2)




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