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Pentax 77mm 1.8 limited $699 B&H
Posted By: lifeofdavid, 07-29-2016, 08:45 AM

Just picked this up

Pentax Telephoto SMCP-FA 77mm f/1.8 Limited Series 27980 B&H


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08-02-2016, 04:57 AM   #16
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QuoteOriginally posted by a5m Quote
That's unfortunate. I also prefer autofocus.

If you haven't already, I'd get in touch with Brian (dcshooter) and send it to him. Eric isn't the end all be all resource for lens repair.
thanks

08-03-2016, 08:03 AM   #17
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This is an FA lens not a DA. So the spec is for full frame not crop. So this is 77mm on full frame. And this applies to all FA and D-FA lenses. Whatever is specified is the focal length for FF.
APS-C has a narrower field of view (that zoom effect or crop). So it is 77 X 1.5 times focal length for an APS-C sensor.

A good ex. of this is DA* 50-135/2.8 (APS-C specification) and D-FA 70-200/2.8 (FF spec). But if you check the FOV
(DA* 50-135) APS-C: 31.5-11.9 / 27-10 (More like 80-210 on FF)
(D-FA* 70-200) Full frame: 34.5 to 12.5 / 28.8 to 10.3

They are essentially in the ball park from a composition point of view.

So bottomline FA-77 is 115ish on APS-C and is a brilliant spec by all standards and hence adored for portraits. FA*85/1.4 becomes 127.5mm on APS-C and is the best spec available for a portrait lens hands down for a prime.
D-FA 100 mm is 150mm on APS-C another brilliant lens for APS-C.
It only makes me wonder why people complain about unavailability of lenses in the Pentax line up. They have all the necessary prime focal lengths in bright apertures. (with the exception of 85mm). And then there is holy trinity. If someone still needs more lenses beyond these options then I am usually dumbfound.

That DA* 50-135 is a gem (and I dread its AF capability) but still call it a gem. It is so light weight and way less intimidating to the subjects offering same FOV as D-FA 70-200 will remain my favorite. If you don't have this lens then you haven't bought much into the APS-C system yet.

Last edited by shardulm; 08-03-2016 at 08:20 AM. Reason: Added ex. and more explanation.
08-03-2016, 08:32 AM   #18
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QuoteOriginally posted by talkskiwon Quote
Does anyone know the exact focal length for APS-C ? around 50 ish?
QuoteOriginally posted by a5m Quote
Focal length is always fixed, whether it's mounted on a FF or crop sensor camera.

Due to the 1.53x crop factor the FA 77 on a APS-C will give you a field of view equivalent to approximately 118mm on FF.

EDIT:
In other words, a 77mm focal length on APS-C will give you the same field of view as a 118mm lens on FF. It can be a bit confusing (really?) but I hope that helps. Check out this article.
QuoteOriginally posted by UncleVanya Quote
You wrote that backwards. 118mm on full frame looks similar to 77 on apsc. The field of view (angle of coverage) is narrower on apsc due to cropping off the parts that don't fit on the sensor.
QuoteOriginally posted by shardulm Quote
This is an FA lens not a DA. So the spec is for full frame not crop. So this is 77mm on full frame. And this applies to all FA and D-FA lenses. Whatever is specified is the focal length for FF.
APS-C has a narrower field of view (that zoom effect or crop). So it is 77 X 1.5 times focal length for an APS-C sensor.
@shardulm - I think you understand this - but your statement has one confusing item that is not relevant. The fact that the FA77 is full frame isn't relevant to the focal length. Pentax lenses are always specified by actual focal length not effective relative to full frame. So a DA 70 which is technically a crop sensor lens provides a 105mm equivalent field of view - which is what you explained about the DA* 50-135 so I assume you understand this but I just want people reading your explanation to understand clearly that full frame or not - the focal length is the same always, only the field of view actually changes in the viewfinder.
08-03-2016, 10:27 AM   #19
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QuoteOriginally posted by UncleVanya Quote
@shardulm - I think you understand this - but your statement has one confusing item that is not relevant. The fact that the FA77 is full frame isn't relevant to the focal length. Pentax lenses are always specified by actual focal length not effective relative to full frame. So a DA 70 which is technically a crop sensor lens provides a 105mm equivalent field of view - which is what you explained about the DA* 50-135 so I assume you understand this but I just want people reading your explanation to understand clearly that full frame or not - the focal length is the same always, only the field of view actually changes in the viewfinder.
The Q/01 8.5mm f/1.9 lens on Q is equivalent to about 47mm on FF. (1:2.3" = 5.5x crop factor)

But it is still an 8.5mm focal length lens

08-03-2016, 11:29 AM   #20
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QuoteOriginally posted by monochrome Quote
The Q/01 8.5mm f/1.9 lens on Q is equivalent to about 47mm on FF. (1:2.3" = 5.5x crop factor)

But it is still an 8.5mm focal length lens
Yup. My Panasonic LX7 is similar in sensor size and has a zoom of 4.7-17.7mm which translates into around 21mm in 16:9 format equivalence to 105mm in 1:1 format equivalence. (or 24-90 in 4:3 aspect ratio and equivalence)
08-03-2016, 01:20 PM   #21
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QuoteOriginally posted by UncleVanya Quote
@shardulm - I think you understand this - but your statement has one confusing item that is not relevant. The fact that the FA77 is full frame isn't relevant to the focal length. Pentax lenses are always specified by actual focal length not effective relative to full frame. So a DA 70 which is technically a crop sensor lens provides a 105mm equivalent field of view - which is what you explained about the DA* 50-135 so I assume you understand this but I just want people reading your explanation to understand clearly that full frame or not - the focal length is the same always, only the field of view actually changes in the viewfinder.
The thing that throws me off with this calculation is that.. the focal length spec and FOV are disjoint if what you say is true. So an FA 77 will focus @77mm regardless of crop or not and is specified so. A 50-135 will focus in that range crop or not right? But FOV for 70-200 and 50-135 is similar when put on respective bodies but both lenses are different focal length spec. Or is it that this 50-135 is really a 70-200 but with a smaller image circle and hence specified so for crop bodies?

Please enlighten.
08-03-2016, 02:01 PM - 1 Like   #22
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QuoteOriginally posted by shardulm Quote
The thing that throws me off with this calculation is that.. the focal length spec and FOV are disjoint if what you say is true. So an FA 77 will focus @77mm regardless of crop or not and is specified so. A 50-135 will focus in that range crop or not right? But FOV for 70-200 and 50-135 is similar when put on respective bodies but both lenses are different focal length spec. Or is it that this 50-135 is really a 70-200 but with a smaller image circle and hence specified so for crop bodies?

Please enlighten.
Gosh - there are a lot of articles about this but I will try.

First putting both the DA* 50-135 and the FA 77 Limited at 77mm and using them on the K-3 you get the same image in the viewfinder as far as the angle of coverage and the magnification seen. This is assuming no focus breathing (another topic) etc. but in all practical ways the images are identical. If you then mount the two on the K-1 and do the same test the FA 77 - shows the same part of the image inside the crop frame - but now shows more outside of it in clear and acceptable focus and quality. The DA* 50-135 still at 77mm will show the same image inside the crop frame but outside of that it will severely vignette and or show a black area where the lens does not provide adequate coverage of the Full Frame image circle.

So both project at a 77mm focal length - but one has a limitation that it only projects a smaller diameter circle that can't fully cover the larger sensor. The objects in the circle that it is projecting are the same size and orientation as the FA 77 makes inside that same circle. The difference is that the FA 77 has a larger circle - including things outside the circle that the DA* 50-135 can project. This larger circle is totally ignored on the APSC camera - it's just wasted hitting the internal walls of the camera's shutterbox.

Another way to conceptualize it is that you are looking out of your house onto a scene through a window. Someone comes along and masks off part of the window with plywood. Your view is reduced of the outside world. You can't see all the same stuff but the stuff you see hasn't changed. The smaller masked off window is APSC, remove the extra plywood and restore your entire window and now you have Full frame. Now imagine that your plywood was removed but there are bushes in the way that block the view - that's like putting an APSC (DA) lens on the camera - you can't get a good view of the area outside of the APSC image circle in most cases - a few lenses are technically APSC but have been found to be quite good or at least acceptable in the Full Frame area. The DA 70 is one of these as is the DA 40. The DA* 60-250 when modified by the removal of a baffle in the rear of the lens seems to work very well on Full frame also.

So taking this back to the angle of view - all lenses have a focal length. That focal length is a strong predictor of the actual field of view for a given sensor size. This is fixed and a property of the lens. The image circle that the lens covers tells you what size sensor you can use with the lens. Too small and the edges won't get any light or will get distorted light.

Take a 300mm designed for a Hassleblad or an 8x10 camera. Put that on the APSC camera - compare that shot to the shot from the DA* 300 - they should be the same roughly. Then try to use the DA* 300 on the large 8x10 camera - a large part of the sensor (film or digital) will be outside the image circle but the central portion will look the same as if you were using the large format lens.

Does this help? If not there are articles that have been written that do a better job that I can do. The important thing to recall is focal length is not changed by the camera sensor size; sensor size affects what you see with the lens; lenses that project smaller image circles can't provide the full view on the larger sensor; and it is dang confusing to discuss.
08-04-2016, 10:52 AM   #23
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QuoteOriginally posted by UncleVanya Quote
The important thing to recall is focal length is not changed by the camera sensor size; sensor size affects what you see with the lens; lenses that project smaller image circles can't provide the full view on the larger sensor; and it is dang confusing to discuss.
Although part of it was redundant information I appreciate you taking time to explain this. And I agree that the focal length does not change with the sensor. What changes is the FOV ONLY. Since everything is spec'd and talked in FF equivalents people tend to cast and convert the focal lengths for the crop sizes. But what they are essentially inferring is the FOV of a lens for the specified focal lengths. So if you need a 24-70 kind of FOV for a FF then get a D-FA 24-70. If you need 24-70 kind of FOV for an APSC body then get a DA* 16-50 is essentially the math.

Having said that does any one know how much the DA 15mm/f4 limited vignette on the FF? Its still 15mm ultra wide with respect to the FF but has a smaller image circle.

08-04-2016, 06:29 PM   #24
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QuoteOriginally posted by shardulm Quote
Having said that does any one know how much the DA 15mm/f4 limited vignette on the FF?
Someone on theses forms said it's horrible. I forget which post I read it in.
08-18-2016, 03:03 PM   #25
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QuoteOriginally posted by pearsaab Quote
I'm trying to be good...i didn't want to see this. I love my 77mm but mine got dunked in the river and although it was cleaned by eric and looks great, the contacts died after 6 months and is now a manual focus lens. I prefer autofucus. Not sure what to do...eek


How much do you want for it?
08-18-2016, 04:00 PM   #26
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QuoteOriginally posted by shardulm Quote
Although part of it was redundant information I appreciate you taking time to explain this. And I agree that the focal length does not change with the sensor. What changes is the FOV ONLY. Since everything is spec'd and talked in FF equivalents people tend to cast and convert the focal lengths for the crop sizes. But what they are essentially inferring is the FOV of a lens for the specified focal lengths. So if you need a 24-70 kind of FOV for a FF then get a D-FA 24-70. If you need 24-70 kind of FOV for an APSC body then get a DA* 16-50 is essentially the math.
One of the great benefits of shooting medium and large format film (6x45, 6x6, 6x9, 6x12, 4x5 and 5x7) is that you quickly learn that focal length does not equal field of view. A 90mm lens could be a telephoto, a "normal" lens, or an extreme wide angle - just depends on the format you're shooting.
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