Pentax M, FA, and D FA* 50mm F1.4 comparison

bdery · 04-14-2019, 05:44 PM

Originally posted by pres589

The copy of the M 50 used seems to be exceptional. It makes me wonder if I've been too harsh in the performance of the copy I have.

It's hard to say if a pârticular lens is a particularly stellar copy, we can only assume that it is representative of the model as a whole.

Originally posted by tokyoscape

Thanks, and I a kind of wish you added *55 in there too. It is not a 50 but it 1.4 and perhaps the right racehorse to the new *50.

There is a "modern 50mm comparison" available with the 55 included. You can use it to compare the 55 with the M and FA 50s.

Wasp · 05-05-2020, 03:55 AM

Originally posted by RGlasel

I can't think of a way to put meaningful DOF marks on a lens without an aperture ring, which is also absent from the D FA. The D FA is limited in how it can be used on Pentax cameras built before the nineties (when was AV mode introduced?).

The thing is - DOF markings need to be different for crop frame and full frame.

phoebus · 05-07-2020, 12:41 AM

Originally posted by Wasp

The thing is - DOF markings need to be different for crop frame and full frame.

You are correct that the DOF calculation is based on the circle of confusion at standard print size; but in these pixel peeping days I would suggest that it is pixel size that changes the assessment.

As K-1 and K-5 have same pixel pitch, stands to reason exactly the same DOF would apply at pixel peeping level.

Wasp · 05-07-2020, 07:12 AM

Originally posted by phoebus

You are correct that the DOF calculation is based on the circle of confusion at standard print size; but in these pixel peeping days I would suggest that it is pixel size that changes the assessment.

As K-1 and K-5 have same pixel pitch, stands to reason exactly the same DOF would apply at pixel peeping level.

Interesting idea, but the math to prove it would induce a major headache. The conventional wisdom goes like this.

Quote:

There are several sneaky ways that format size sneaks into the DOF math:

Enlargement factor
Focal Length
Subject-to-camera / focal distance

Depth of Field, Part III: The Myths | B&H Explora

The enlargement factor is open to interpretation. Pixel peeping certainly covers that.

**dms** · 05-07-2020, 01:35 PM

DOF markings for FF apply to APSC if choose 1 stop more open than actual taking aperture. E.g., if taking at f/16 use DOF marking for f/11. This is exact for 1.414 crop sensor, so close enough for 1.5 crop.

**RGlasel** · 05-07-2020, 04:30 PM

Way back in the last century, before there was an Internet and phones were black and mounted on a wall, I started shooting 35mm film with a Braun rangefinder camera that didn't even have a light meter and the DOF markings were a teaching tool. But even then the link between the amount of the image that was in focus and what the DOF markings indicated was pretty weak. In my opinion, DOF markings are the most useless lens feature possible. Experience and taking lots of photographs are far more effective ways to get a grip on depth of field.

bdery · 05-08-2020, 05:08 AM

Originally posted by dms

DOF markings for FF apply to APSC if choose 1 stop more open than actual taking aperture. E.g., if taking at f/16 use DOF marking for f/11. This is exact for 1.414 crop sensor, so close enough for 1.5 crop.

I respectfully think you put too much faith in anyone's ability to rad accurately those markings. The margin of error is just too high.

05-07-2020, 07:12 AM	#19
Wasp Pentaxian Join Date: Mar 2017 Location: Pretoria Photos: Gallery Posts: 4,661	Originally posted by phoebus You are correct that the DOF calculation is based on the circle of confusion at standard print size; but in these pixel peeping days I would suggest that it is pixel size that changes the assessment. As K-1 and K-5 have same pixel pitch, stands to reason exactly the same DOF would apply at pixel peeping level. Interesting idea, but the math to prove it would induce a major headache. The conventional wisdom goes like this. Quote: There are several sneaky ways that format size sneaks into the DOF math: Enlargement factor Focal Length Subject-to-camera / focal distance Depth of Field, Part III: The Myths \| B&H Explora The enlargement factor is open to interpretation. Pixel peeping certainly covers that.

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04-14-2019, 05:44 PM	#16
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,357	Originally posted by pres589 The copy of the M 50 used seems to be exceptional. It makes me wonder if I've been too harsh in the performance of the copy I have. It's hard to say if a pârticular lens is a particularly stellar copy, we can only assume that it is representative of the model as a whole. Originally posted by tokyoscape Thanks, and I a kind of wish you added 55 in there too. It is not a 50 but it 1.4 and perhaps the right racehorse to the new 50. There is a "modern 50mm comparison" available with the 55 included. You can use it to compare the 55 with the M and FA 50s.

05-05-2020, 03:55 AM	#17
Wasp Pentaxian Join Date: Mar 2017 Location: Pretoria Photos: Gallery Posts: 4,661	Originally posted by RGlasel I can't think of a way to put meaningful DOF marks on a lens without an aperture ring, which is also absent from the D FA. The D FA is limited in how it can be used on Pentax cameras built before the nineties (when was AV mode introduced?). The thing is - DOF markings need to be different for crop frame and full frame.

05-07-2020, 12:41 AM	#18
phoebus Pentaxian Join Date: Jun 2013 Location: Buckinghamshire (UK) / Morbihan (FR) Photos: Gallery Posts: 470	Originally posted by Wasp The thing is - DOF markings need to be different for crop frame and full frame. You are correct that the DOF calculation is based on the circle of confusion at standard print size; but in these pixel peeping days I would suggest that it is pixel size that changes the assessment. As K-1 and K-5 have same pixel pitch, stands to reason exactly the same DOF would apply at pixel peeping level.

05-07-2020, 01:35 PM	#20
dms Site Supporter Join Date: Aug 2011 Location: New York, NY Photos: Gallery Posts: 2,192	DOF markings for FF apply to APSC if choose 1 stop more open than actual taking aperture. E.g., if taking at f/16 use DOF marking for f/11. This is exact for 1.414 crop sensor, so close enough for 1.5 crop.

05-07-2020, 04:30 PM	#21
RGlasel Site Supporter Join Date: Sep 2013 Location: Saskatoon Photos: Gallery \| Albums Posts: 3,228	Way back in the last century, before there was an Internet and phones were black and mounted on a wall, I started shooting 35mm film with a Braun rangefinder camera that didn't even have a light meter and the DOF markings were a teaching tool. But even then the link between the amount of the image that was in focus and what the DOF markings indicated was pretty weak. In my opinion, DOF markings are the most useless lens feature possible. Experience and taking lots of photographs are far more effective ways to get a grip on depth of field.

05-08-2020, 05:08 AM	#22
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,357	Originally posted by dms DOF markings for FF apply to APSC if choose 1 stop more open than actual taking aperture. E.g., if taking at f/16 use DOF marking for f/11. This is exact for 1.414 crop sensor, so close enough for 1.5 crop. I respectfully think you put too much faith in anyone's ability to rad accurately those markings. The margin of error is just too high.