[pentaxk3user]

Hi I'm looking for someone that has a k3 and the pentax 50-135 2.8 and a sigma 18-35 1.8 that would help me do a little comparison . Before I go out and buy the 50-135 I wanted to see the difference in the 2 lens once the sigma is cropped from a 35mm to the same size as the 135 mm . I would like for the pentax to stay at 2.8 at 135mm and the sigma at 35mm with a few different f stops starting at 1.8 and stop down to what ever you think looks the sharpest for the sigma . If possible a outside shot of a brick building or house from about 50 yards away and maybe one of a landscape from where ever you live . I just want to see if you have to pixel peep to see a difference in the photos with the 35 mm cropped to the length and width that you get from the 135 mm zoom and see what f stop I would need on the 35 mm compared to the f2.8 setting on the 135 . If you have both lens but not a k3 I'll take the comparison on any pentax camera . Thanks for your help .

[Sandy Hancock]

You'd have to crop the bejeezus out a 35mm shot to give a 135mm equivalent. And the depth of field would be equivalent to about f/8.0. Not even worth considering if image quality is a consideration - which it should be if you're shooting such high quality lenses.

Just get the 50-135.

[pentaxk3user]

You'd have to crop the bejeezus out a 35mm shot to give a 135mm equivalent. And the depth of field would be equivalent to about f/8.0. Not even worth considering if image quality is a consideration - which it should be if you're shooting such high quality lenses.

Just get the 50-135.

Sandy I have a sigma 70-200 2.8 and I did a comparison with it at 200 mm f4 on both and it looked pretty close . I'm going to take a few more like this . I should have keep the 200mm at 2.8 and I think the 35mm might be sharper closed down another stop . I'm trying to see if I would be happy with the 18-35 for a single travel lens or not . https://flic.kr/p/2hE4c4t https://flic.kr/p/2hE4c3w

[Sandy Hancock]

I'm trying to see if I would be happy with the 18-35 for a single travel lens or not.

That's a *really* big travel lens, but whatever floats (or sinks?) your boat.
I would find 18mm quite limiting at the wide end, and 35mm crushingly limiting at the long end. Where are you planning to travel?

[Serkevan]

There's a world of difference between those two pictures, although the 18-35 sure is sharp to even compete.

[pentaxk3user]

That's a *really* big travel lens, but whatever floats (or sinks?) your boat.
I would find 18mm quite limiting at the wide end, and 35mm crushingly limiting at the long end. Where are you planning to travel?

Do you think the 18-35 is a really big travel lens ? Its smaller than the 50-135 I think . On my k3 its really 27- 52.5 . My daughter just had our first Grand baby . We live in KY and both my daughters live in Seattle Washington . They have some pretty good places to take photos out there But I would say I'm leaning more on using the lens on the baby the 18-35 might work better . I think with the 1.8 I won't need a flash and I can get pretty close with the 18-35 . the 50 on the 50-135 is really 75 so I;m not sure if that's going to let me get a full baby in frame unless I get way back . I just don't know . I do have the pentax 50 mm 1.8 that I can stick on the carry on camera bag along with the 18-35 . I have been looking at a lot of photos from the 50-135 2.8 and they just look so good but don't know if its that big a difference in the photos of things at longer distances . I just wanted to see the difference in the 2 lens from someone that knew what they are doing to see if they could make the 35 cropped to 135 to get close to the 135 mm . I'm not going to pixel peep on far away buildings or mountains . Do you know how the 50-135 works on close up baby faces or full body baby length Its a new born so he is still small .

[Sandy Hancock]

I was in Seattle not long ago. Nice town, but most shots I took on walk-arounds there were wider than 18mm. But for chasing babies around indoors I actually reckon the 18-35/1.8 would be pretty useful if you're happy with your copy's AF.

As for size - the dimensions are similar but the Sigma is quite a bit heavier. And the comparison shots you posted pretty much confirmed my comments about deep cropping vs a longer lens.

For your needs though, I reckon the DA16-85 would be much more useful. Or the 18-135 if you're looking for something really compact.

[pentaxk3user]

I was in Seattle not long ago. Nice town, but most shots I took on walk-arounds there were wider than 18mm. But for chasing babies around indoors I actually reckon the 18-35/1.8 would be pretty useful if you're happy with your copy's AF.

As for size - the dimensions are similar but the Sigma is quite a bit heavier. And the comparison shots you posted pretty much confirmed my comments about deep cropping vs a longer lens.

For your needs though, I reckon the DA16-85 would be much more useful. Or the 18-135 if you're looking for something really compact.

Sandy I just looked at some photos from the DA16-85 that might be the way to go . I would like to see the difference in its 85mm compared to the 35 mm cropped also .

[Serkevan]

Well, cropping from 35 to 85 mm will leave you with something like... 5, 6 MP on your K-3? Approximately.

[Sandy Hancock]

I would like to see the difference in its 85mm compared to the 35 mm cropped also .

If I understand things correctly, you'd lose about 75% of the pixels, and f/2.8 with the Sigma will look like f/5.6 with the 16-85 @ 85, but with much less detail.

That's not going to be pretty.

[pentaxk3user]

Well, cropping from 35 to 85 mm will leave you with something like... 5, 6 MP on your K-3? Approximately.

Serkevan Are you saying if you take a photo that's 24 mp on a 35mm lens and if you crop it to 85mm size it makes it 5.6 mp ? How does that work can you give me a link so I can read about it ? Does cropping make the photo less sharp ? Is 5.6 mp still good enough for say a anything less than a 8x10 . I never print anything bigger than a 8x10 .

[Serkevan]

Yes, approximately. You can have a visual representation here: Nikon | Imaging Products | NIKKOR Lens Simulator (I know, Nikon, but hey, the tool is useful here )

At 35 mm, your angle of view will be approximately 44º (on an APS-C body like your K-3). At 85 mm, your angle of view will be approximately 19º. So, to get the 35 mm image to show you only the part that corresponds to the 85mm image, you will have to crop down to approximately 44% of the original image (35mm/85mm= 44%).

Your K-3 creates images measuring 4000 x 6016 pixels. With the 16-85 at 85 mm this is the size of your entire frame. With the 18-35 cropped to show the same, you will have a "window" of 1760 x 2645 pixels, which is a 4.7 MP image. This should still be enough to print, at 300 dpi (for a good quality image), to a 5.9x8.8 paper. To print this crop at 8x10 you might have to downscale to around 220 dpi, which will have an impact in the picture quality. In fact, the image quality from your crop at 8x10 will be the same as printing the entire frame at 18x27, give or take.

Not only that, but you will be getting very close to the pixel peeping level just because of the cropping, which means that any small problems with focusing, blur, aberrations, etc. will be magnified: this will probably turn a perfectly good 35 mm picture into a lousy 85 mm photo covered in purple streaks from the fringing. The crop you posted shows this, the 200 mm crop of the 18-35 would make a technically bad picture.

All in all, I would recommend the 16-85 or even two lenses (18-35 + 55-300 perhaps?) to avoid this problems.

[Kozlok]

I have the 18-35 and the 16-85. When the sun is up, the Sigma stays in the hotel. It really is a boat anchor. At night I use it as a fast wide and leave all my other lenses behind. The Sigma is almost as heavy as the 16-85 AND the 12-24 or the Sigma 8-16. That’s a far more versatile pair.

[bdery]

Sandy I have a sigma 70-200 2.8 and I did a comparison with it at 200 mm f4 on both and it looked pretty close .

That can't be right.

When cropping 35mm to get a FOV similar to 200mm, you are going from a field of view of 38° to a field of view of 6.9°. Calculating roughly, if you have a K-3 or similar sensor (24 MP), then your crop will give you an equivalent of 4.36 MP.

That's less than Pentax's first DSLR...

There is no way that the 18-35 at 4.36 effective MP will outperform the 70-200 at 24 MP. Maybe it would outperform a Coke bottle, but not anything else.

I'm guessing you cropped, then exported to a low resolution (or looked at the images at less than full res, etc) and didn't see any difference.

Serkevan Are you saying if you take a photo that's 24 mp on a 35mm lens and if you crop it to 85mm size it makes it 5.6 mp ?

No, he is saying that the DOF will be somewhat comparable to a 85mm lens at F5.6.

[pentaxk3user]

If I understand things correctly, you'd lose about 75% of the pixels, and f/2.8 with the Sigma will look like f/5.6 with the 16-85 @ 85, but with much less detail.

That's not going to be pretty.

I don't understand what you typed yet but I'm going to try to figure it out . I'm going to read the links Serkevan put above . I still have a lot to learn . So sorry if my questions and requests are stupid .

---------- Post added 11-01-19 at 07:11 AM ----------

I have the 18-35 and the 16-85. When the sun is up, the Sigma stays in the hotel. It really is a boat anchor. At night I use it as a fast wide and leave all my other lenses behind. The Sigma is almost as heavy as the 16-85 AND the 12-24 or the Sigma 8-16. That’s a far more versatile pair.

Kozlok will you take a photo with the 18-35 at 35mm and the sharpest f stop and then take the same photo with the 16-85 at 85 mm with the f stop at 2.8 . them crop the 35 mm photo so you see the same thing as you do with the 85mm . And post it here so I can see the difference in the two .

---------- Post added 11-01-19 at 07:21 AM ----------

That can't be right.

When cropping 35mm to get a FOV similar to 200mm, you are going from a field of view of 38° to a field of view of 6.9°. Calculating roughly, if you have a K-3 or similar sensor (24 MP), then your crop will give you an equivalent of 4.36 MP.

That's less than Pentax's first DSLR...

There is no way that the 18-35 at 4.36 effective MP will outperform the 70-200 at 24 MP. Maybe it would outperform a Coke bottle, but not anything else.

I'm guessing you cropped, then exported to a low resolution (or looked at the images at less than full res, etc) and didn't see any difference.



No, he is saying that the DOF will be somewhat comparable to a 85mm lens at F5.6.

I know the 200mm photo is better than the cropped 35mm to the same size fov as the 200mm and I can see it when I zoom in on flikr and lightroom but not zooming in it looks pretty close . I was just hoping to get 2 photos from you professionals that know what your doing to let me see what the difference is between a 18-35mm lens at 35mm cropped to the same fov as the pentax 50-135 at 135mm . or even the 85mmm from the 16-85 mm lens .