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03-29-2015, 01:25 PM   #16
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QuoteOriginally posted by severalsnakes Quote
Hmm... I do understand that the f/stop is a fractional whatchamacallit. The MX-1's widest focal length is 6mm, though, not 12. As the aperture opening is a function of a fraction, I did not believe any sort of equivalence computation was necessary, as it would be when we are comparing "equivalent" fields of view with focal lengths...?

1/2 is 1/2 no matter if it is 1/2 of 100 or 1/2 of 1,000,000.

This has the potential to be VERY confusing.
You're right that the MX-1 is 6mm, that's what I did my calculations with, though I erroneously wrote 12mm.

It can be very confusing. The f-number represents the relationship between the focal length of the lens and the physical size of the opening. That's it. This is why you can't just compare f-numbers in determining which lenses gather more light. Lower f-numbers mean more light gathering only at equivalent focal lengths.

03-29-2015, 01:30 PM   #17
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QuoteOriginally posted by hbarnwheeler Quote
You're right that the MX-1 is 6mm, that's what I did my calculations with, though I erroneously wrote 12mm.

It can be very confusing. The f-number represents the relationship between the focal length of the lens and the physical size of the opening. That's it. This is why you can't just compare f-numbers in determining which lenses gather more light. Lower f-numbers mean more light gathering only at equivalent focal lengths.
Yeah, I puzzled it out and edited my original reply. Thanks!
03-29-2015, 01:45 PM - 1 Like   #18
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It confused me too, but I told myself,
To hell with all that math!
My MX takes great low light pics too.

03-29-2015, 05:51 PM - 6 Likes   #19
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Took the kit lens out this afternoon!

Click here to see the kit lens album.

Highlights:













03-29-2015, 06:14 PM   #20
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I really like the look of those photos. Is it the camera, or is it just you?
03-29-2015, 06:15 PM   #21
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QuoteOriginally posted by severalsnakes Quote
Took the kit lens out this afternoon!

Click here to see the kit lens album.
Wow! Nice work.
03-29-2015, 06:28 PM   #22
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QuoteOriginally posted by normhead Quote
I really like the look of those photos. Is it the camera, or is it just you?
Thank you! I'd like to say it's just me. ;-)

QuoteOriginally posted by hbarnwheeler Quote
Wow! Nice work.
Thanks!
03-30-2015, 12:32 PM   #23
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QuoteOriginally posted by severalsnakes Quote
Took the kit lens out this afternoon
Looks like the lens can be quite capable but it looks like there's some limitations to it also. But isn't that the same with any lens - learning the lens and how to make the most of it is half the fun of photography. If I ever get the K-S2, I'd be interested in getting it with the kit lens, it looks like it could be a useful addition. Thanks for the pictures, they are definitely useful.

03-30-2015, 03:35 PM   #24
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Quick question: How is the cd-af (in live view), compared to other Pentax DSLRs, if you know?
03-30-2015, 03:44 PM - 1 Like   #25
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QuoteOriginally posted by yorik Quote
Quick question: How is the cd-af (in live view), compared to other Pentax DSLRs, if you know?
I have minimal-to-0 experience, since the kit lens is my only auto-focus lens and I have not used it on the K-30 at all yet.

In good light it seemed great; in indoor light it searched, but did not fail to "lock on"... Again, minimal experience with this lens, CD-AF, and auto-focus lenses/settings in general.

Might be better to wait for someone else to weigh-in...
03-30-2015, 04:29 PM   #26
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Thanks!
03-31-2015, 12:29 AM   #27
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A couple of the boomerangs I used to make (sorry about the border) DA35mm Ltd f8 ISO100 fluorescent light

03-31-2015, 03:06 PM   #28
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QuoteOriginally posted by hbarnwheeler Quote
You're right that the MX-1 is 6mm, that's what I did my calculations with, though I erroneously wrote 12mm.

It can be very confusing. The f-number represents the relationship between the focal length of the lens and the physical size of the opening. That's it. This is why you can't just compare f-numbers in determining which lenses gather more light. Lower f-numbers mean more light gathering only at equivalent focal lengths.
I think your over complicating things. F-number is a measure of exposure; they exist (as a ratio of diameter and focal length) to remove focal length from the equation. I think it's down to the physics of how lenses work; larger focal lengths need a bigger "hole" to allow the same amount of light to the sensor ( a wide angle lens gathers more light and focuses it on the sensor). Try putting a zoom lens on your camera and using Av mode dial in a constant aperture (e.g 5.6) . Point the camera at a White wall and zoom in and out; the shutter speed and ISO doesn't change- i.e. Same exposure.

In theory swapping lenses and setting the same aperture, ISO and shutter speed should give the same exposure. However this doesn't take into account the transmittance of the lens ( how much the glass elements and coatings etc eat up light), thus in real life you will often have adjust exposure.

Back to the mx-1, the wide end 6mm f1.8 is equivalent to a 35mm camera equipped with 28mm lens with a max aperture of f1.8 in terms of exposure and f8.3 in terms of depth of field. I.e. A high quality small sensor camera with a good fast lens attached is really useful in situations where your want a large depth of field ( as you'd have to stopper down a large sensor camera and potentially raise ISO; reducing difference in picture quality) and where a less intimidating appearance can put people at ease. They also tend to behave better in full auto, which you could enable and pass the camera to somebody else and be present in the photos!

Anyways.... Back to wishing I could afford a k-s2 ( and mx-1 for that matter!)
03-31-2015, 07:33 PM - 2 Likes   #29
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K-S2, Promaster 24/2.8





K-S2, Accura Diamatic 135/2.8



04-01-2015, 10:34 AM   #30
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QuoteOriginally posted by DanGleabols Quote
I think your over complicating things. F-number is a measure of exposure; they exist (as a ratio of diameter and focal length) to remove focal length from the equation. I think it's down to the physics of how lenses work; larger focal lengths need a bigger "hole" to allow the same amount of light to the sensor ( a wide angle lens gathers more light and focuses it on the sensor). Try putting a zoom lens on your camera and using Av mode dial in a constant aperture (e.g 5.6) . Point the camera at a White wall and zoom in and out; the shutter speed and ISO doesn't change- i.e. Same exposure.
This is definitely food for thought. One would think bigger hole = more light, but if it's true that larger lenses need relatively larger apertures for the same amount of light, then that won't be true. I wonder why they would, though.

---------- Post added 04-01-15 at 01:35 PM ----------

QuoteOriginally posted by severalsnakes Quote
K-S2, Promaster 24/2.8





K-S2, Accura Diamatic 135/2.8



These are fantastic. Are those M42 lenses?
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