What would happen if I were to use a crop lens with tc on the K1?

funkythiru · 10-02-2017, 01:22 PM

Just a hypothetical scenario I was entertaining in my head.

**jatrax** · 10-02-2017, 01:27 PM

The camera would explode. No really...................

If the camera is in crop mode then the result would be very similar to that from the K-5 series. If not in crop mode then it depends on the lens but most likely there would be at least some vignetting or in some cases a lot of vignetting. But each lens will be different so testing will be required to see how good or bad the result would be.

**boriscleto** · 10-02-2017, 01:34 PM

Pentax isn't Canon. Mounting a DA lens on a K-1 won't damage the camera the way mounting a EF-S lens on a Canon FF can.

**pepperberry farm** · 10-02-2017, 02:45 PM

you'd probably see some vignetting?

what were you expecting?

funkythiru · 10-02-2017, 02:50 PM

Even if I were to drop in light density/ concentration.

pschlute · 10-02-2017, 03:30 PM

Originally posted by funkythiru

If the teleconverter covered the ff sensor would vignetting be negated?

Using a crop-sensor lens with a FF teleconverter could reduce or eliminate vignetting entirely depending on the lens. I just tried the 10-17 FE lens on the K1 with a 1.7 FF TC. No vignetting visible in the viewfinder even at 10mm. Have not tried a picture though.

On the K1 you can choose FF mode or Crop mode or auto mode where the camera will choose the mode depending on the lens connected.

Note that "crop-sensor" lens is not a definitive description. A number of crop-sensor lenses produced by pentax do in fact cover the FF sensor with no or very little vignetting.

What exactly are you trying to achieve ?

Sandy Hancock · 10-02-2017, 05:00 PM

I just had a look with the K-1 + teleconverter with the following lenses:

DA10-17
DA15
DA21
DA35 macro

The teleconverter causes significant light loss in the corners - after all, it is not designed to cover the full frame. That vignetting persists with whatever lens you put in front of it. Not surprisingly, the hard physical vignetting from the crop lenses is almost eliminated, because the sensor is only seeing the central portion of the image circle. Just the same as using crop mode without the teleconverter, but slightly less because the crop factor is 1.4, not 1.5.

There is no reason to suspect the result will be any different with any other crop lens.

So basically, you get almost the same image as you would in crop mode, with a heap of light loss in the corners.
In other words, it's a pointless exercise.

funkythiru · 10-02-2017, 05:11 PM

Using a 50mm crop lens for portrait shooting. Hypothetically

**Bob 256** · 10-02-2017, 05:19 PM - **1 Like**

Let's make an interesting comparison between the K-1 which has a 36.4 Megapixel sensor, and the K-01 which is an APS-C sized sensor of 16 Megapixels.

The only difference is an extra "build" of pixels around the APS-C sensor area in the K-1 which gives extra area to form an image on. The pixel density of those two camera sensors is identical, and if the same lens is used on both cameras (regardless of whether it's a crop lens or not), an identical image is formed within the APS-C area (assuming exposure and processing is identical), and a print made from either camera based on the APS-C area would contain the same number of pixels and the same image. If the K-1 is operated in crop mode, it just throws away the extra pixels around the APS-C area but the cropped image would be identical to one taken with the K-01. If the K-1 is operated in full-frame mode, it will show picture elements beyond this area (assuming a non-crop lens is used) or an area where vignetting takes place (if a crop lens is used).

If a print is made from either of these cameras, it would be identical if crop mode was used in the K-1.

If a full-frame print from the K-1 were compared to a "full-frame" APS-C print from the K-01, the former would appear to have less magnification (this assumes the lens used allows FF with the K-1). In this case, we have more pixels, and the image is reduced to make room for the extras that are built around the APS-C image to contribute to the 36 Megapixel FF image of the K-1.

If, however, in post-processing, we decide to crop the K-1 image so it shows the same scale as the K-01, we're back to the same APS-C sensor size and 16 Megapixels - an equivalent image to what the K-01 would deliver with that same lens. It really doesn't matter if the photo is cropped in the K-1 or in post-processing - same pixel count - same magnification - same appearance as the smaller sensor photo.

Bottom line for me is to shoot FF and worry about cropping later. The downside is a larger file and the requirement to know some of the shown image is going to be lost later if cropping is done in post-processing (if the lens vignettes, that's the portion that will disappear, we hope).

If, however, you're shooting with any lens or lens combination that you know you'll remove the K-1's FF "extra", it could be wise to shoot crop to save on memory card space. In that case, it would be an image based on 16 Mpix rather than the larger 36 Mpix image.

Sandy Hancock · 10-02-2017, 05:21 PM

Originally posted by funkythiru

Using a 50mm crop lens for portrait shooting. Hypothetically

Go for it. You'll get bigger files with more vignetting and more glass to interfere with the image, but hey, if that's what you want....

I'd stick with crop mode, or a crop body.

**jatrax** · 10-02-2017, 05:25 PM - **1 Like**

Originally posted by funkythiru

Using a 50mm crop lens for portrait shooting. Hypothetically

Just use the K-1 in crop mode. Simple. The teleconverter will result in roughly the same field of view but with some vignetting, light loss and whatever reduced image quality results from the extra glass.

An interesting hypothetical question but when light meets sensor just go with the simple solution.

leekil · 10-02-2017, 05:29 PM

Originally posted by Sandy Hancock

So basically, you get almost the same image as you would in crop mode, with a heap of light loss in the corners.
In other words, it's a pointless exercise.

Which teleconverter did you use?

**pcrichmond** · 10-02-2017, 05:57 PM - **1 Like**

Originally posted by funkythiru

Just a hypothetical scenario I was entertaining in my head.

It would depend on the TC and lens.
I tried a Bower 8mm aps-c fisheye with a Tamron 1.4TC in FF mode and had very good results with almost no vignetting.
Other members responded with similar results with other lenses.
Here is the thread with photos attached so you can see the vignetting yourself.
Go for it, experimentation is half the fun.
8mm APS FE + 1.4TC + K1 - PentaxForums.com

Sandy Hancock · 10-02-2017, 07:43 PM

Originally posted by leekil

Which teleconverter did you use?

The HD Pentax-DA 1.4x Rear Converter. I specified "not designed to cover the full frame" in my post.

A full frame TC would avoid the vignetting, but still adds extra glass. Apart from a few extra megapickles, what's the point of not using a crop camera?

**NoCo Pentaxian** · 10-02-2017, 09:45 PM

I think the solution is obvious: Pentax needs to make a 0.5x teleconverter for the K1 that would disperse the light from crop lenses onto a full frame sensor. (j/k)

10-02-2017, 01:22 PM	#1
funkythiru Senior Member Join Date: Feb 2017 Location: Chicago Posts: 291	What would happen if I were to use a crop lens with tc on the K1? Just a hypothetical scenario I was entertaining in my head.

10-02-2017, 02:50 PM	#5
funkythiru Senior Member Join Date: Feb 2017 Location: Chicago Posts: 291 Original Poster	If the teleconverter covered the ff sensor would vignetting be negated? Even if I were to drop in light density/ concentration.

10-02-2017, 05:19 PM - 1 Like	#9
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Let's make an interesting comparison between the K-1 which has a 36.4 Megapixel sensor, and the K-01 which is an APS-C sized sensor of 16 Megapixels. The only difference is an extra "build" of pixels around the APS-C sensor area in the K-1 which gives extra area to form an image on. The pixel density of those two camera sensors is identical, and if the same lens is used on both cameras (regardless of whether it's a crop lens or not), an identical image is formed within the APS-C area (assuming exposure and processing is identical), and a print made from either camera based on the APS-C area would contain the same number of pixels and the same image. If the K-1 is operated in crop mode, it just throws away the extra pixels around the APS-C area but the cropped image would be identical to one taken with the K-01. If the K-1 is operated in full-frame mode, it will show picture elements beyond this area (assuming a non-crop lens is used) or an area where vignetting takes place (if a crop lens is used). If a print is made from either of these cameras, it would be identical if crop mode was used in the K-1. If a full-frame print from the K-1 were compared to a "full-frame" APS-C print from the K-01, the former would appear to have less magnification (this assumes the lens used allows FF with the K-1). In this case, we have more pixels, and the image is reduced to make room for the extras that are built around the APS-C image to contribute to the 36 Megapixel FF image of the K-1. If, however, in post-processing, we decide to crop the K-1 image so it shows the same scale as the K-01, we're back to the same APS-C sensor size and 16 Megapixels - an equivalent image to what the K-01 would deliver with that same lens. It really doesn't matter if the photo is cropped in the K-1 or in post-processing - same pixel count - same magnification - same appearance as the smaller sensor photo. Bottom line for me is to shoot FF and worry about cropping later. The downside is a larger file and the requirement to know some of the shown image is going to be lost later if cropping is done in post-processing (if the lens vignettes, that's the portion that will disappear, we hope). If, however, you're shooting with any lens or lens combination that you know you'll remove the K-1's FF "extra", it could be wise to shoot crop to save on memory card space. In that case, it would be an image based on 16 Mpix rather than the larger 36 Mpix image. Attached Images Last edited by Bob 256; 10-02-2017 at 05:43 PM.

10-02-2017, 05:57 PM - 1 Like	#13
pcrichmond Site Supporter Join Date: Sep 2014 Location: Bishop, CA Posts: 278	What would happen with aps lens and TC on K-1 Originally posted by funkythiru Just a hypothetical scenario I was entertaining in my head. It would depend on the TC and lens. I tried a Bower 8mm aps-c fisheye with a Tamron 1.4TC in FF mode and had very good results with almost no vignetting. Other members responded with similar results with other lenses. Here is the thread with photos attached so you can see the vignetting yourself. Go for it, experimentation is half the fun. 8mm APS FE + 1.4TC + K1 - PentaxForums.com Last edited by pcrichmond; 10-02-2017 at 06:04 PM.

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10-02-2017, 01:27 PM	#2
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	The camera would explode. No really................... If the camera is in crop mode then the result would be very similar to that from the K-5 series. If not in crop mode then it depends on the lens but most likely there would be at least some vignetting or in some cases a lot of vignetting. But each lens will be different so testing will be required to see how good or bad the result would be.

10-02-2017, 01:34 PM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Pentax isn't Canon. Mounting a DA lens on a K-1 won't damage the camera the way mounting a EF-S lens on a Canon FF can.

10-02-2017, 02:45 PM	#4
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,643	you'd probably see some vignetting? what were you expecting?

10-02-2017, 03:30 PM	#6
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,192	Originally posted by funkythiru If the teleconverter covered the ff sensor would vignetting be negated? Using a crop-sensor lens with a FF teleconverter could reduce or eliminate vignetting entirely depending on the lens. I just tried the 10-17 FE lens on the K1 with a 1.7 FF TC. No vignetting visible in the viewfinder even at 10mm. Have not tried a picture though. On the K1 you can choose FF mode or Crop mode or auto mode where the camera will choose the mode depending on the lens connected. Note that "crop-sensor" lens is not a definitive description. A number of crop-sensor lenses produced by pentax do in fact cover the FF sensor with no or very little vignetting. What exactly are you trying to achieve ?

10-02-2017, 05:00 PM	#7
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,267	I just had a look with the K-1 + teleconverter with the following lenses: DA10-17 DA15 DA21 DA35 macro The teleconverter causes significant light loss in the corners - after all, it is not designed to cover the full frame. That vignetting persists with whatever lens you put in front of it. Not surprisingly, the hard physical vignetting from the crop lenses is almost eliminated, because the sensor is only seeing the central portion of the image circle. Just the same as using crop mode without the teleconverter, but slightly less because the crop factor is 1.4, not 1.5. There is no reason to suspect the result will be any different with any other crop lens. So basically, you get almost the same image as you would in crop mode, with a heap of light loss in the corners. In other words, it's a pointless exercise.

10-02-2017, 05:11 PM	#8
funkythiru Senior Member Join Date: Feb 2017 Location: Chicago Posts: 291 Original Poster	Using a 50mm crop lens for portrait shooting. Hypothetically

10-02-2017, 05:21 PM	#10
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,267	Originally posted by funkythiru Using a 50mm crop lens for portrait shooting. Hypothetically Go for it. You'll get bigger files with more vignetting and more glass to interfere with the image, but hey, if that's what you want.... I'd stick with crop mode, or a crop body.

10-02-2017, 05:25 PM - 1 Like	#11
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by funkythiru Using a 50mm crop lens for portrait shooting. Hypothetically Just use the K-1 in crop mode. Simple. The teleconverter will result in roughly the same field of view but with some vignetting, light loss and whatever reduced image quality results from the extra glass. An interesting hypothetical question but when light meets sensor just go with the simple solution.

10-02-2017, 05:29 PM	#12
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	Originally posted by Sandy Hancock So basically, you get almost the same image as you would in crop mode, with a heap of light loss in the corners. In other words, it's a pointless exercise. Which teleconverter did you use?

10-02-2017, 07:43 PM	#14
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,267	Originally posted by leekil Which teleconverter did you use? The HD Pentax-DA 1.4x Rear Converter. I specified "not designed to cover the full frame" in my post. A full frame TC would avoid the vignetting, but still adds extra glass. Apart from a few extra megapickles, what's the point of not using a crop camera?

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10-02-2017, 09:45 PM	#15
NoCo Pentaxian Loyal Site Supporter Join Date: Dec 2015 Location: Colorado Photos: Gallery \| Albums Posts: 80	I think the solution is obvious: Pentax needs to make a 0.5x teleconverter for the K1 that would disperse the light from crop lenses onto a full frame sensor. (j/k)