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09-12-2009, 05:06 PM   #1
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Da35 middle distance...

On PPG and flickr I see lots of close work for the DA-35, and lots of infinity shots, but not a many in the middle distance, i.e., for me that's 7-15' or so. Does anybody have some examples, or any sense if this distance doesn't isn't the DA35 strong suit? Thanks,
Brian

09-12-2009, 08:00 PM   #2
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QuoteOriginally posted by FHPhotographer Quote
On PPG and flickr I see lots of close work for the DA-35, and lots of infinity shots, but not a many in the middle distance, i.e., for me that's 7-15' or so. Does anybody have some examples, or any sense if this distance doesn't isn't the DA35 strong suit? Thanks,
Brian
The DA 35 is excellent at all ranges image-wise. However, this lens does not quite function as a non macro traditional 35mm lens in the near range. The lens architecture is responsible for this.

Whereas a regular 35mm would have a fairly broad depth of field at any given aperture, the 35DA has a considerably shallower depth of field at an equal aperture at mid range distances.

It is quite versitile, and the image quality is impeccable in every way; contrast, color, no distortion and spot on sharpness.

EDIT: Here is an image I found using a DA35 at the distances you spoke of.


Stephen

Last edited by SCGushue; 09-13-2009 at 07:41 AM. Reason: Add Image
09-13-2009, 11:12 AM   #3
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Thanks for the feedback. I'm new at this aspect of the craft, so bear with me here: does the "considerably shallower depth of field..." suggest it's more difficult for the lens to find a focus point, or that I would have to be more careful in selecting exactly what object/point I want? I'm guessing there is data out there on DOF for every lens? If so, I should be able to compare lenses, e.g. at 10-15' the DA-35 has a DOF of X contrasted with the FA-35 of Y at the same aperture and range.
Thanks again, retirees need this sort of thing to keep focused,
Brian
09-13-2009, 12:28 PM   #4
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QuoteOriginally posted by SCGushue Quote

Whereas a regular 35mm would have a fairly broad depth of field at any given aperture, the 35DA has a considerably shallower depth of field at an equal aperture at mid range distances.
What is your source for this information?

09-13-2009, 03:06 PM   #5
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is this correct, or not?

QuoteOriginally posted by clm Quote
What is your source for this information?
Are you suggesting this is not correct? I haven't found anything online to either support or refute it. Just a lot of folks saying that focal length+f-stop+object distance = DOF, but nobody is saying if that is inclusive or not.

Let me rephrase the question using those responses to this point: assuming the same sensor and same distance and f-stop, do different models (DA / FA) of the same focal length have the same DOF or not?

Somewhere somebody must know,
Brian

Last edited by FHPhotographer; 09-13-2009 at 03:17 PM. Reason: clarification
09-13-2009, 04:50 PM   #6
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Yes, they do. It would require a revolution in the laws of physics (or in lens design, anyhow) for two different 35mm lenses to produce different DOF at the same aperture and subject distance.
09-13-2009, 05:19 PM   #7
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QuoteOriginally posted by Marc Sabatella Quote
Yes, they do. It would require a revolution in the laws of physics (or in lens design, anyhow) for two different 35mm lenses to produce different DOF at the same aperture and subject distance.
With all due respect Marc look at the hyperfocal scales on these lenses. Then commenton your findings.


Stephen

Last edited by SCGushue; 09-13-2009 at 05:30 PM. Reason: will post images
09-13-2009, 05:46 PM   #8
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QuoteOriginally posted by clm Quote
What is your source for this information?

Head to head testing of the DA35 with the K35.

Near distances DOF are markedly shallow as expected. Mid distances are nearly equal but slightly shallower. Far distances, beyond 10 feet are nearly identical, though not quite so until approaching infinity.

Stephen

09-13-2009, 08:18 PM   #9
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QuoteOriginally posted by SCGushue Quote
With all due respect Marc look at the hyperfocal scales on these lenses. Then commenton your findings.


Stephen
Those scales are format dependent. FA lens scale is based on 135 format, DA lens scale is based on APS-C format.

One of the top threads in this very sub-forum addresses this issue. Go to the link on the first post in that thread, you can see that the very first input parameter for DOF is image format size.
09-13-2009, 08:23 PM   #10
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QuoteOriginally posted by FHPhotographer Quote
On PPG and flickr I see lots of close work for the DA-35, and lots of infinity shots, but not a many in the middle distance, i.e., for me that's 7-15' or so. Does anybody have some examples, or any sense if this distance doesn't isn't the DA35 strong suit? Thanks,
Brian

FHPhotographer: I don't know if I follow the logic of the middle distance DOF differences. By saying that, I am simply saying I don't know if this is true or not. The Online Photographer had a nice series on DOF very practical, recently. It was said the most important factors were distance to subject and focal length followed by aperture last. MJ makes the argument - not me. As far as the DOF scales and hyperfocal distance, the older full frame lenses' scales are not accurate on a cropped sensor. There was a thread on this here and links to others that make the argument.

I do have the DA 35 mm and really enjoy it for its close focus non macro shots. I shoot a lot at distances 7-15'. MobileMe Gallery Not the best but I have an album named for the DA 35 mm and also more recently some shots in the album titled Sloss Furnace. Maybe these can help. Overall a fine lens at any distance, imho.
09-13-2009, 08:24 PM   #11
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QuoteOriginally posted by dave9t5 Quote
Those scales are format dependent. FA lens scale is based on 135 format, DA lens scale is based on APS-C format.

One of the top threads in this very sub-forum addresses this issue. Go to the link on the first post in that thread, you can see that the very first input parameter for DOF is image format size.
Ah, you beat me to it.
09-13-2009, 10:06 PM   #12
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QuoteOriginally posted by SCGushue Quote
Head to head testing of the DA35 with the K35.

Near distances DOF are markedly shallow as expected. Mid distances are nearly equal but slightly shallower. Far distances, beyond 10 feet are nearly identical, though not quite so until approaching infinity.

Stephen
If I understand the assertion, the DA-35 does have a more shallow DOF than a K-35 at minimum focus distance, with the difference slowly narrowing until at infinity they are virtually identical? Other posters, however, maintain this is not correct and there is no difference. Are we now arguing the scale on the lenses rather than the actual image? If so, maybe both arguments are correct; if not, my original question assuming the same sensor and same distance and f-stop, do different models [DA / FA] of the same focal length have the same DOF? is still in dispute,
Brian
09-14-2009, 06:52 AM   #13
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QuoteOriginally posted by FHPhotographer Quote
If I understand the assertion, the DA-35 does have a more shallow DOF than a K-35 at minimum focus distance, with the difference slowly narrowing until at infinity they are virtually identical? Other posters, however, maintain this is not correct and there is no difference. Are we now arguing the scale on the lenses rather than the actual image? If so, maybe both arguments are correct; if not, my original question assuming the same sensor and same distance and f-stop, do different models [DA / FA] of the same focal length have the same DOF? is still in dispute,
Brian
I can't, and won't, argue with those who make statements to the contrary. I do my own testing on every lens I use. I do that because I make a living with them and have so for 31 years.

Regardless of sensor/film format a 35mm doesn't give a rat's petutney about format size. Sensor size does effect DOF, but does it care about the lens used? No, but in the case of the DA35 it is formulated for a flat DOF from corner to corner and the optics are maximized for macro utilization. As you move away from macro the differences in DOF narrow/over distance, but they are not exactly as a standard 35mm. My lab tests have proven that. For all intents and purposes it is genrally not a significant difference but there is a difference none the less and in critcal work that is important to me.

One other aspect to consider (and I would prefer the DA35 any day of the week regardless) is that barrel throw of the DA35 concentrates everything at distance beyond 2' in the last 5% of barrel rotation. The hyperfocal markings act as only a guide and using the lens in manual mode dictates perfect visual focus by the user as you cannot rely on the HF barrel marking for any assistance what so ever. The K35 (great lens) has nearly 50% if it's barrel throw clearly delineating HF distances between 2feet and 15 feet + infinity. Much easier to use in critcal manual focusing at the distances you spoke of.

In the end... will the average user be aware of the differences? Most likely not. The DA 35 is one of the VERY BEST optical gems produced by Pentax in their long and storied career.

Best regards,

Stephen

Last edited by SCGushue; 09-14-2009 at 07:25 AM.
09-14-2009, 09:07 AM   #14
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QuoteOriginally posted by SCGushue Quote
I can't, and won't, argue with those who make statements to the contrary. I do my own testing on every lens I use.
Then it should be a simple matter to produce the test shots that led you to this conclusion. If you can demonstrate this, I'll gladly rescind my statement, as I readily admit I've never performed the test. But it just flies in the face of everything that I have read, experienced, or calculated. Similarly, I've never been to Mars, but overwhelming evidence suggests that it is as science reports it to be.

And as noted, DOF scale markings are format-dependent. Since DOF is also dependent on print size and viewing distance as well as viewer visual acuity, they are also not particularly objective as a measure of the actual optical characteristics of the lens - they are just approximations to mark the DOF that would result from whatever the lens designer decided were "typical" values for those variables.

QuoteQuote:
in the case of the DA35 it is formulated for a flat DOF from corner to corner and the optics are maximized for macro utilization. As you move away from macro the differences in DOF narrow/over distance, but they are not exactly as a standard 35mm.
It is certainly true that the *shape* of the zone of acceptable focus may differ between macro and non-macro lenses. And due to the curvature of the field in the non-macro lens, it may *apear* to be have more DOF, because objects on the edge of the frame may be in focus at nearer distances than on the flatter field of a macro lens. But you should get corresponding less at the back end on the edge, so the actual DOF should be the same. And even if the corner performance is different due to this curvature, the center DOF should be the same. That's what the theory says, that's what every test I've ever seen show, and that's what your tests have to disprove.
09-14-2009, 08:33 PM   #15
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QuoteOriginally posted by SCGushue Quote
the barrel throw of the DA35 concentrates everything at distance beyond 2' in the last 5% of barrel rotation.
I think that's the only drawback. The throw is really short at mid-long distances. I'm ok with it, but it's something to at least be aware of
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