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10-26-2010, 08:51 AM   #1
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Samyang 85mm vs DA* 55mm at F1.4

Hello all,

I'm interested in buying a large-aperture portrait lens, and I'm looking at these two. The difference in price for the DA* 55mm would be covered by selling the DA 70.

I have limited experience with F1.4 (I actually recently sold the FA 50 1.4to fund the DA 15, but that was before I got really interested in this for portraits...and I didn't really like the FA 50 at 1.4 either).

My question is, can I get this look...

Smiling bokeh | Flickr - Photo Sharing!

...with the DA* 55? Or do I need to go to the 85 to get this narrow a depth of field? The photo in the link is with a D700, so I realize I can't exactly duplicate the look re: DOF (or can I? Would an A 135mm 2.8 work?), but I'd like to get close. Any of you with extensive large aperture experience want to chime in? Thanks!

Todd

10-26-2010, 09:42 AM   #2
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AFAIK it's the number and shape of the aperture blades that largely determine the bokeh, not so much the max. aperture.

Whilst I don't have one I understand the new 100mm Macro WR has superb bokeh because of the rounded aperture blades. Whether this would make a good portrait lens I'm not sure; a lot depends on what your working distance (from the subject) would be.

At least one of the sample shots taken with the 55mm (see Lenses section) shows comparable bokeh with your example.

Last edited by JohnX; 10-26-2010 at 09:48 AM.
10-26-2010, 09:54 AM   #3
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it would rely on the distance and aperture opening. you will still be able to isolate the subject but not as shallow as that on a FullFrame, although focus would be more forgiving on the APS-C.

as for lens suggestion for wide open portraits use with great bokeh and isolation, get a cheap manual focus lens 55/1.8.
10-26-2010, 11:04 AM   #4
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QuoteOriginally posted by gnaztee Quote
Hello all,

I'm interested in buying a large-aperture portrait lens, and I'm looking at these two. The difference in price for the DA* 55mm would be covered by selling the DA 70.

I have limited experience with F1.4 (I actually recently sold the FA 50 1.4to fund the DA 15, but that was before I got really interested in this for portraits...and I didn't really like the FA 50 at 1.4 either).

My question is, can I get this look...

Smiling bokeh | Flickr - Photo Sharing!

...with the DA* 55? Or do I need to go to the 85 to get this narrow a depth of field? The photo in the link is with a D700, so I realize I can't exactly duplicate the look re: DOF (or can I? Would an A 135mm 2.8 work?), but I'd like to get close. Any of you with extensive large aperture experience want to chime in? Thanks!

Todd
If you have the budget for it then get the DA*55mm or the Sigma 50mm f/1.4. You could wait for the Sigma 85mm f/1.4 which appears to be a very good lens. The 85mm will give you better results if DoF is your primary goal. IF money is no object then the A* 135mm f/1.8 is the best lens, but you will be a little father away from your subject.

10-27-2010, 10:55 AM   #5
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Thanks for replies

I guess I'm just trying to get a handle on the equivalent DOF between 85mm f1.4 on FF and 55mm f1.4 on APS-C.

I know that more distance between the subject and background increases bokeh...I know that less distance between lens and subject increases bokeh...I know that FF increases bokeh over aps-c...I can't seem to get my head around how these all play together when trying to compare the above combinations. I realize that every subject and background will cause variables.

I'm trying to figure this out because I think the 55mm would be more versatile (and I want the DA* over a cheaper manual because I could sell my DA 18-55 WR and still have a sealed lens), but I really want the bokeh. So if I have to get the Samyang (new Sigma out of price range) to get the bokeh, then I'll go with that.

Thanks again...
10-27-2010, 11:05 AM   #6
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You wont get what a FF with a 85 1.4 would give you, but it will still allow for some DOF control. I`d go with 85 1.4 and reconsider selling the DA70.

All your choices of course.
10-27-2010, 11:15 AM   #7
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QuoteOriginally posted by JohnX Quote
AFAIK it's the number and shape of the aperture blades that largely determine the bokeh, not so much the max. aperture.
This is quite incorrect. Background Bokeh is largely determined by optical formula of the lens itself. Some lenses are over-corrected for aberration and might not have as smooth of a bokeh, while under-corrected would have smoother bokeh with the usual less sharpness. Of course, the inherent DOF is determined by aperture, while the number and shape of blades only dictates the shape of point light. That is not at all important since the shot was taken at near WO (f/1.6).

Back to the OP, you can definitely get similar look with the 55/1.4. However, ISO would play its part in the picture as well. To full body like that with a shallower DOF, you can take 4 or more pictures and stitch them together (I forgot the name of the technique). Of course, it has to be done with practice. But don't go too wild with shallow DOF. This picture would be less interesting if the DOF is thinner.
10-27-2010, 11:30 AM   #8
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QuoteOriginally posted by gnaztee Quote
I guess I'm just trying to get a handle on the equivalent DOF between 85mm f1.4 on FF and 55mm f1.4 on APS-C.

I know that more distance between the subject and background increases bokeh...I know that less distance between lens and subject increases bokeh...I know that FF increases bokeh over aps-c...I can't seem to get my head around how these all play together when trying to compare the above combinations. I realize that every subject and background will cause variables.

I'm trying to figure this out because I think the 55mm would be more versatile (and I want the DA* over a cheaper manual because I could sell my DA 18-55 WR and still have a sealed lens), but I really want the bokeh. So if I have to get the Samyang (new Sigma out of price range) to get the bokeh, then I'll go with that.

Thanks again...
The way that FF "increases bokeh" over APS-C is by allowing you to get closer and still keep the same framing. Given the same lens, aperture, and distance to subject, the only thing that will change is the framing.

10-27-2010, 11:38 AM   #9
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QuoteOriginally posted by farfisa Quote
The way that FF "increases bokeh" over APS-C is by allowing you to get closer and still keep the same framing. Given the same lens, aperture, and distance to subject, the only thing that will change is the framing.
It's not quite that simple though - from my understanding of reading the about the Circle of Confusion, the sensor size affects it as well, as expressed by this equation:

CoC (mm) = viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25
10-27-2010, 01:14 PM   #10
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Well, it all depends on which CoC you are talking about. Going to larger sensor size actually increases the CoC on the image side while keeping the same focal length would mean smaller CoC on the object side.

Dr. Nasse from Zeiss Optics actually wrote an article on this subject, Depth of Field and Bokeh:

Depth of Field and Bokeh by Dr. Nasse

It's an excellent read that would clear lots of confusions out there. Myth such as "9 blades guarantee smooth bokeh" is definitely not true at all.
10-27-2010, 04:29 PM   #11
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Hi. Todd. On an APS-C camera as opposed to Full Frame i do agree that the 70 to 90 focal length is a good way to get creamy circular bokeh. Although I will agree that the optical formula does play a part so choosing your lens may be a tough call. I have no issue with the DA70's results for bokeh however the best I have at the moment is the Tamron SP90 2.8 which has a lovely bokeh.
it is in this light that I wish to suggest a few articles to help you understand DOF and bokeh and how they relate. While aperture does play a large part it is not the only factor
I found these articles quite helpful

The Online Photographer: Depth-of-Field Hell
And
The Online Photographer: Depth of Field Hell?The Sequel

I think the example you found on Flikr is great but Full frame is capable of a more shallow depth of field and the same 85 1.4 lens on APS-C will behave differently. Not to mention the photo was post processed quite well!

I hope this helps
Cheers
Roger
10-27-2010, 06:52 PM   #12
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Roger, thanks for the links, the first one especially solidifies what I was thinking about this...so the 135mm 2.8 would probably give me something like a rough approximation in terms of DOF that we see in the link I originally posted. Aperture would be smaller, but the extra distance would make up for it (roughly). Expounding this further, I should be able to shoot my DA 55-300 at 300mm and f5.8 and get narrow DOF too (but I'd be a block away!).

I didn't mean to make my quest sound like it was about quality of bokeh...it was more about how narrow a DOF I can get with my subject's full body easily in the frame. The quality is good, and you're right, I like what the DA 70 gives, but I know that the 85/1.4 or 55/1.4 would have narrower DOFs at similar focal lengths.

Thanks!
10-28-2010, 11:51 AM   #13
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looking at the pictures in the link you have provided, they were shot with 85mm lens on FF camera. DA*55 will provide you very similar FOV on your APSC Pentax to that. f1.4 on 55APSC will have bit deeper DOF than f1.4 on FF but I think the DA* would easilly deliver what you are after. Putting the 85mm on APSC you would have to flinch back quite a bit more to get full body in!
10-28-2010, 12:39 PM   #14
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I really, really like the Samyang/Rokinon 85/1.4 on my D700 (so much that I sold my Nikon 85/1.8 AF), but I haven't used it on APS-C.
10-28-2010, 02:04 PM   #15
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QuoteOriginally posted by gnaztee Quote
I guess I'm just trying to get a handle on the equivalent DOF between 85mm f1.4 on FF and 55mm f1.4 on APS-C.
Alright here goes...The depth of field is the same.

A 35mm lens at f1.4, and 55mm lens at f1.4 and an 85mm lens at f1.4 all have the same absolute depth of field if you are framing the same subject on the same format (i.e. a headshot with an APS-C camera).

The only thing that will change will be the amount of background visible. So decide if you like the look of a 85mm lens or the look of a 55mm lens. You can decide this from using a zoom and looking carefully at the background.
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