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03-27-2017, 10:46 AM   #1
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35mm f2 vs 35mm f1.4 depth of field

To start off, I realize that Pentax has no 35mm f1.4, at least not one realistically available. But the question I have is if anyone has any direct comparisons between the depth of field differences between these two apertures when a 35mm lens is used. Either full frame examples or crop sensor examples would be nice to see. I know I can use a dof calculator but I want real world examples of how much more of a narrow depth of field I can get with an f1.4 over f2, and how well the subject can be isolated from the background. Basically I just want to see if the Pentax 35mm f2 will meet my needs to allow more into my frame but still give good subject isolation. It would be used on my crop cameras for now. Thanks

03-27-2017, 11:00 AM   #2
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QuoteOriginally posted by stillshot2 Quote
To start off, I realize that Pentax has no 35mm f1.4, at least not one realistically available. But the question I have is if anyone has any direct comparisons between the depth of field differences between these two apertures when a 35mm lens is used. Either full frame examples or crop sensor examples would be nice to see. I know I can use a dof calculator but I want real world examples of how much more of a narrow depth of field I can get with an f1.4 over f2, and how well the subject can be isolated from the background. Basically I just want to see if the Pentax 35mm f2 will meet my needs to allow more into my frame but still give good subject isolation. It would be used on my crop cameras for now. Thanks
That difference in aperture will not make as much a difference as your camera-subject / subject-background distance will. Even the 35mm f/2.4 does a great job at isolating the subject. This was shot at f/3.2 on the K-1, plenty of shallow dof effect to play with
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03-27-2017, 11:27 AM   #3
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QuoteOriginally posted by stillshot2 Quote
To start off, I realize that Pentax has no 35mm f1.4, at least not one realistically available.
Pentax DA 35mm f2.4, FA 35mm f2, FA 31mm limited, Samyang 35mm f1.4, Sigma 30mm f1.4 (old and new art version), Sigma 35mm f1.4 art (here),.. I think Mitakon makes a 35mm lens, as well, but it has no automation at all; as well as older legacy lenses.

QuoteOriginally posted by stillshot2 Quote
Basically I just want to see if the Pentax 35mm f2 will meet my needs to allow more into my frame but still give good subject isolation
QuoteOriginally posted by enoeske Quote
That difference in aperture will not make as much a difference as your camera-subject / subject-background distance will.
This is a good reply. At minimum focus distance and a nice background, you will get plenty of bokeh. But if you are in bright light (and need to stop down), and are focusing on something 25m away from you, you will not get a shallow DoF. If you are focusing on something far-away you will generally not get shallow DoF unless you are using telephoto lens or tilt lens. Big part of photography is composition - finding the right subject, placing it in the right position, with good background, and in good light. If your technique is great, you can work it even with a less than perfect lens.

Anyway, the FA 35mm f2 is a fairly well regarded lens. Buying it used from USA or Japan will probably give you a pretty fair price, as well. Buying a brand new one in EU doesn't make as much sense, as it costs way more than the DA 35mm here..

If you want really shallow DoF at a low low price but still with good IQ, think about DA 50mm f1.8 and FA 50mm f1.4. Yes, not as wide angle as the 35mm, but much faster aperture at a low cost. Big difference between f2.4 and f1.8. And the extra 15mm focal length gives you even more bokeh, shallower DoF.

I have DA 35mm f2.4 and Flektogon 35mm, but I almost always use them at f5.6 or f8. I don't do shallow DoF photography, because it quickly becomes a gimmick
03-27-2017, 12:15 PM   #4
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QuoteOriginally posted by stillshot2 Quote
To start off, I realize that Pentax has no 35mm f1.4, at least not one realistically available.
Please feel free to make an offer for my Pentax-M 35mm f1.4 M 35/1.4

03-27-2017, 12:37 PM - 2 Likes   #5
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The FA35 f2 does have an advantage of being very small (compared to say a Samyang 35 f1.4) and is surprisingly useful on the K-1 (my most used lens):
03-27-2017, 03:08 PM - 2 Likes   #6
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QuoteOriginally posted by stillshot2 Quote
To start off, I realize that Pentax has no 35mm f1.4, at least not one realistically available. But the question I have is if anyone has any direct comparisons between the depth of field differences between these two apertures when a 35mm lens is used. Either full frame examples or crop sensor examples would be nice to see. I know I can use a dof calculator but I want real world examples of how much more of a narrow depth of field I can get with an f1.4 over f2, and how well the subject can be isolated from the background. Basically I just want to see if the Pentax 35mm f2 will meet my needs to allow more into my frame but still give good subject isolation. It would be used on my crop cameras for now. Thanks
That is a tough one. There is more to subject isolation than DOF. As you are probably aware, the better calculators say 2mm difference in DOF for a subject at 0.5m and f/1.4 vs. f/2 on APS-C. How that translates into foreground/background blur is independent of the limits of acceptable sharpness.

Having said my piece on your main question, there is something else that you might want to consider. How do you intend to focus an f1.4 lens? Your K-30 has fairly poor focus sensitivity with PDAF (ability to detect OOF is the same at f/5.6 maximum aperture as at f/1.4 or f/2.0). The implications for missed focus are bad enough at f/2.0 and somewhat worse at f/1.4. If fine focus is the intent, then there are two options, magnified live view and/or aftermarket split-image screen.

I have a number of film cameras and have f/1.4, f/1.8, and f/2.0 at or near the 55mm focal length (similar FOV to 35mm on the K-30) to fit them. All are vintage, but none are slouches either. The short story is that I very seldom shoot with the f/1.4 glass. Focus is a pain and they are not that sharp wide open to f/2.8. There is a drop in contrast too. Mind you, neither approaches the Sigma 35/1.4 in optical performance, but that does not make the Sigma any easier to focus with. The bottom line is that there is little to be gained by putting up the big bucks for a top quality f/1.4 unless you have a definitely use case and know why you want to spend the money.


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03-27-2017, 03:17 PM - 1 Like   #7
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QuoteOriginally posted by kiwi_jono Quote
The FA35 f2 does have an advantage of being very small (compared to say a Samyang 35 f1.4) and is surprisingly useful on the K-1 (my most used lens):
@kiwi_jono very nice photo. I used to have a FA35 f2, your image make me miss that lens.
03-27-2017, 06:03 PM   #8
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QuoteOriginally posted by Na Horuk Quote
Pentax DA 35mm f2.4, FA 35mm f2, FA 31mm limited, Samyang 35mm f1.4, Sigma 30mm f1.4 (old and new art version), Sigma 35mm f1.4 art (here),.. I think Mitakon makes a 35mm lens, as well, but it has no automation at all; as well as older legacy lenses.
I was referring to this bad boy: SMC Pentax-M 35mm F1.4 Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database. I'm not too fond of "off brand" lenses though, so I'd like to keep my options exclusive to Pentax. The Sigma art is tempting to me but looks pretty large and heavy, and quite a bit more cash.

QuoteOriginally posted by pschlute Quote
Please feel free to make an offer for my Pentax-M 35mm f1.4 M 35/1.4
Seriously?! You have one? Please do share a photo!

QuoteOriginally posted by stevebrot Quote
he bottom line is that there is little to be gained by putting up the big bucks for a top quality f/1.4 unless you have a definitely use case and know why you want to spend the money.
Thanks for the insight. This is what I was leaning towards, and these few examples shared from the FA 35mm f2 are pretty good examples of what I was looking for, albeit shot from a K1 which I really want but can't quite afford :/ I have a few fast 50's but there's those times when you just can't back up enough indoors! haha

Anyone have good crop sensor samples taken with the 35mm f2? I am still leaning towards picking one up as soon as I sell another 50mm lens of mine, since the FA 35 is full frame ready for when that time comes

03-27-2017, 06:22 PM   #9
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You might find these examples from the Sigma 35/1.4 helpful.

Sigma 35mm F1.4 DG HSM "Art" Review - Sample Photos | PentaxForums.com Reviews

Here are a couple wide open from my FA 35/2 on APS-C:







To be honest, I seldom shoot with the FA 35/2 wide open. F/2.8 is generally wide enough if I want background blur.


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03-27-2017, 06:57 PM   #10
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QuoteOriginally posted by stevebrot Quote
Here are a couple wide open from my FA 35/2 on APS-C:
Ok thanks. It looks like those photos are at short focusing distances, correct? Oh, and how many clicks are on the aperture ring between f2 and f4 on the FA 35mm f2?
03-27-2017, 06:59 PM   #11
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This is an example w/ 35mm at f/2 (it is the K version). Believe focus is on the front (near end) of the subway station--although it is 1/10 sec hand held--but it gives I think a feeling typical of this lens under such lighting. (It is on APS-C sensor.)
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Last edited by dms; 03-27-2017 at 07:09 PM.
03-27-2017, 07:36 PM   #12
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My apologies--I had forgotten the image I attached above was a significant crop--so it is deceptive--vis-a-vis your question.The full image is here.
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03-27-2017, 08:09 PM   #13
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QuoteOriginally posted by pschlute Quote
Please feel free to make an offer for my Pentax-M 35mm f1.4 M 35/1.4
You actually have this lens? Could you post a review? Would be really interesting to see anything about this lens...
03-27-2017, 08:53 PM   #14
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QuoteOriginally posted by IgorZ Quote
You actually have this lens? .
Only in my dreams
03-27-2017, 09:15 PM   #15
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QuoteOriginally posted by stillshot2 Quote
Ok thanks. It looks like those photos are at short focusing distances, correct? Oh, and how many clicks are on the aperture ring between f2 and f4 on the FA 35mm f2?
The wasp nest was about a meter away, the others were at or near MFD. The number of clicks? On my K-3, it is six clicks (2 stops at 1/3 stop per click) . The aperture ring is in half-stop steps through f/11.


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