Sigma 24mm f/3.5 lens on fpL

I used the Sigma fpL with a new 24mm f/3.5 (Contemporary) lens in "downtown" Vienna, Virginia recently. An old RR train caboose is parked along the former RR line, now a walking/bike trail. Trivia fact: an early US Civil War ambush/battle took place along this RR line about a mile from here, also through our neighborhood.

I'm very impressed with the sharpness of the lens and I like using the aperture ring! I don't have that feature on any other lenses to date. You put the camera in Aperture mode and then can set the aperture by the ring, without using a dial on camera. It's far easier to set and see your aperture in bright sunlight. I'm going through photos, studying different resolution choices I used, framing, etc. More photos to come. I give file sizes which may be of interest to others considering the camera.


Sigma fpL + 24mm/3.5 @ f/5.6 final crop from full resolution (9.5k) file of 96.30MB = 28.50MB

Sandy Fleischmann | Flickr

Yes, it's a very neat lens.

Don

I think the last time I took photos of the red caboose was in 2022 with the (then new) 30mm (Art) lens on the Sigma SD15. The 30mm came with the sdQuattro I'd just bought and I wanted to test it out on the SD15. Worked nicely. Couple photos:




and a few of the Freeman House (19th century building) also in the SD15 album. Basically, a comparison would show that anything looks good at online viewing. The key difference in resolution for me is the ability to zoom and crop and still have decent sized files.

SandyF said:

I used the Sigma fpL with a new 24mm f/3.5 (Contemporary) lens in "downtown" Vienna, Virginia recently. An old RR train caboose is parked along the former RR line, now a walking/bike trail. Trivia fact: an early US Civil War ambush/battle took place along this RR line about a mile from here, also through our neighborhood.

I'm very impressed with the sharpness of the lens and I like using the aperture ring! I don't have that feature on any other lenses to date. You put the camera in Aperture mode and then can set the aperture by the ring, without using a dial on camera. It's far easier to set and see your aperture in bright sunlight. I'm going through photos, studying different resolution choices I used, framing, etc. More photos to come. I give file sizes which may be of interest to others considering the camera.


Sigma fpL + 24mm/3.5 @ f/5.6 final crop from full resolution (9.5k) file of 96.30MB = 28.50MB

Sandy Fleischmann | Flickr

Click to expand...

Looks very good in post view. With my current internet speed, I gave up on 'original' size. So no Tedogram for this one ... maybe later.

My first Sigma 50mm f/2.8 Macro came with an aperture ring - shoulda kept it, I reckon.

--
What you got is not what you saw.

xpatUSA said:

SandyF said:

I used the Sigma fpL with a new 24mm f/3.5 (Contemporary) lens in "downtown" Vienna, Virginia recently.

I'm very impressed with the sharpness of the lens ...


Sigma fpL + 24mm/3.5 @ f/5.6 final crop from full resolution (9.5k) file of 96.30MB = 28.50MB

Click to expand...

Looks very good in post view. With my current internet speed, I gave up on 'original' size. So no Tedogram for this one ... maybe later.

Click to expand...

later:



Showing good detail up to about half the max possible for that size image.

Also found a slant edge to get an MTF reading:



Edge response OK but MTF somewhat lacking for some reason (not necessarily the lens).

--
What you got is not what you saw.

Sorry, what is an edge reading and MTF?

MTF = Modulation Transfer Function. A function is usually something you can draw as a graph.

In this case, the graph plots the contrast of details in an image against their size. If the contrast of small details is high, you have a sharp image.

Usually, the curve in the graph is high at the left hand end, where the larger areas of tone in the image lie, and descends down at the right hand end as patches of tone get progressively smaller.

The vertical axis of the graph is contrast and the horizontal axis is size of patches of tone.

If you plotted the MTFs of a Foveon image and an ordinary Bayer image of the same test chart, you could see how much better the Foveon is.

I do wonder if Ted is trying to blind us with science. Watch out for the English sense of humour ! :-D

Don

Thank you Don, and Ted as well. I really do try to understand technical details, but most go way 'over my head.'

British humour, I like. Husband and I watch many UK programs on US TV. He loves Doc Martin, I like anything with Scottish accents. We discovered the lowland scots language can be almost non-understandable when we were in Edinburgh in 2019. I grew up hearing my uncle's Inverness accent, so Edinburgh's accent was a surprise. My father's sister married a Cameron Highlander.... A. MacKenzie.

SandyF said:

Sorry, what is an edge [response] reading and MTF?

Click to expand...

The edge response graph at right is an indication of lens sharpness when responding to a sharp edge in the scene. No lens can show a hard sharp edge - it's always an 'S' shape and the degree of sharpness is represented by the distance in pixels it takes to go from 10% to 90% which should not be less than 1.26 px - if it shows less than that or if there are over/undershoots,, the image has been over-sharpened.

The MTF at left shows how much the scene contrast is transferred versus frequency (e.g. a picket fence, roof tiles. etc) to the image. If the scene frequency is more that half the sampling frequency of the sensor, the aliasing occurs (the Nyquist limit). As MTF falls with increasing frequency, detail contrast falls and below 10% MTF detail can not be seen. Notice that, based on the edge I measured, the MTF indeed falls below 10% at less than the Nyquist frequency - meaning tiny detail in that area will become invisible on your screen, like the vanishing cherries and wire recently discussed.

No disrespect to the lens, you weren't necessarily focused on the light pole.

Often, lenses are characterized with a single number - the so-called MTF50 - the frequency e.g. lw/mm at which you get half the scene contrast.

--
What you got is not what you saw.

SandyF said:

Thank you Don, and Ted as well. I really do try to understand technical details, but most go way 'over my head.'

Click to expand...

Don posted while I was typing a response to your question.

Hope it helps.

xpatUSA said:

SandyF said:

Thank you Don, and Ted as well. I really do try to understand technical details, but most go way 'over my head.'

Click to expand...

Don posted while I was typing a response to your question.

Hope it helps.

Click to expand...

We all try to be helpful around here.

Don