[pentaxk3user]

Okay I'm trying to follow along as best I can with all the numbers but I'm not at that level yet , I want to be and I'm going to look into what you all are talking about . Are you all saying you won't take a few photos for me to compare ? I was not wanting to compare to a 200mm lens just up to the 135mm and now the 85mm from the 16-85mm . I think I'm getting why cropping is not so good now . I didn't realize I was losing mp's . I thought the part I keep was not changing and the reason it was less mp once cropped was because I was getting rid of a lot of the photo and the mp's were in that part I cut out . I really didn't know what I was thinking I just always cut it and made it big enough to see what I wanted to see. For smaller things like birds at a distance I would use my 70-200 2.8 but for things bigger and farther away like buildings or landscape or barns I would just use my 18-35 and crop how I wanted because every time I tried to use the 70-200 I would never get all I wanted in the photo and found myself backing up way farther away than I wanted to . My nephew's run cross country so I use the 18-35 for that and I would just crop to include what I wanted I tried the 70-200 for that also and when they came by they were just to close and I would only get half their body in the frame . I guess I just like the 18-35 because I get more than I need and just cut out what I don't want . I didn't know I was hurting the photo by cropping it . I cropped this one a lot but to me it still looks okay to me . I got his whole body (he is the smaller one ) With the 70-200 I would have just got his upper half . I probably used the wrong f stop This was my first time using the 18-35 . so I really didn't know what to set it at . I think I just picked f3.5 and 2000 and let the camera pick the iso . I like the TAv mode for action shots so far . I have sense been told to go to f 6 to help with getting things in focus for moving objects . _IMG3075 | myridevlx600 | Flickr

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

Thanks bdery what you said helped I think I see what you all are telling me .

---------- Post added 11-01-19 at 11:41 AM ----------

How does the 50-135 2.8 compare in weight and size to the sigma 70-200 2.8 . The sigma to me is just to heavy to take for traveling by air . If the 50-135 is lighter and smaller I'll just get it and take both .

[taktoon]

50-135 is in fact my favorite lens. Not mostly used but I love it. Bought mine used in excellent condition with still great working SDM for 450$. I don't find it heavy or big at all. If you don't want to shoot fast moving subjects you can't go wrong with this lens.

[ChristianRock]

He calculated the horizontal angle of view. 38 degrees for 35mm lens and 6.9 on 200mm lens on APS-C sensor. Then he made proportion with image size. The cropped one lost 82% of it size. But which size? The proper answer is 82% of the width and 82% of the height so 97% of the surface (mega pixels). I still can be mistaken.

Actually, I think you are right now that I think of it. 35 to 70mm crop you lose 75% of the area, then if you crop to 140mm it's compounded to losing 93.75%. I don't have the exact formula to get to 200mm but somewhere between 96-97% sounds about right, actually.

I think you are actually very close to the right number, so I apologize!

[taktoon]

Actually, I think you are right now that I think of it. 35 to 70mm crop you lose 75% of the area, then if you crop to 140mm it's compounded to losing 93.75%. I don't have the exact formula to get to 200mm but somewhere between 96-97% sounds about right, actually.

I think you are actually very close to the right number, so I apologize!

Hi! You don't have to apologise. No offense taken. I made a lot of mistakes in calculations in my life. Here I just wanted to point that in the end of this cropping you have much less then sometimes acceptable 4.6 mega pixels. Quite good formula is to divide focal lengths and then square the result and multiply by the original number of megapixels. So (35/200)² * 24MP = 0.735MP.

[Sandy Hancock]

How does the 50-135 2.8 compare in weight and size to the sigma 70-200 2.8. The sigma to me is just too heavy to take for traveling by air. If the 50-135 is lighter and smaller I'll just get it and take both.

I do have an image to help with this. The DFA*70-200 is a little bigger than the Sigma, but not by much - about 5mm in each dimension.



As for weight, the DA*50-135 is less than half the weight of the Sigma. 685 vs 1430 according to the reviews

[mikesbike]

Good representation of size difference. The DA* 50-135mm is shown on the KP, as these days I most often use it. I consider it quite compact for a fast tele zoom lens of such quality. Its starting at 50mm makes it versatile for APS-C use. One good thing is it doesn't change its length nor does anything of its exterior move during AF or when it is zoomed. Balance stays the same, and you can hold the lens comfortably. The AF/MF switch is conveniently located for instant use.

It should be a dynamite combo- the Sigma 18-35mm f/1.8 and this excellent Pentax DA* lens.

[Kozlok]

As for weight, the DA*50-135 is less than half the weight of the Sigma. 685 vs 1430 according to the reviews

The Sigma 18-35 weighs in at 811, not 1400. The Sigma 70-200 may come in at 1400...

Derp...Never mind, I see you were off on a different question.

[pentaxk3user]

Okay I found my 2 dng files of the house I put a link to I was comparing. and open them in lightroom . The 35mm was 26.1 mb and 25.9 with the 200mm . After I cropped the 35 to the same fov as the 200 mm photo I saved it as a jpeg and it came out to be 833kb and 1026x670 , and the 200mm came out to be 16.4 mb and 6016x4000 . So I see now what you all are talking about . One thing I don't understand is the 1026x670 and 6016x4000 numbers . Why aren't the numbers the same since I'm seeing the same fov after cropping the photo . Are the numbers a length and width size or the amount of pixels in the photo ? I really need to watch a good video that explains this .Does anyone know of a good video to watch or a good link to read ?

[taktoon]

It is the width and height of images in pixels. Try to zoom in both of them and you will see the difference in quality.

[pentaxk3user]

Well, when you are cropping you are throwing part of the picture away. When you crop a 35mm image to 200mm you are throwing away over 80% of the image - you are cutting it off. That is why you end up with a little over 4 megapixels on a 24 megapixel image. and 4 megapixels was state of the art... about 20 years ago when digital cameras first started and everybody still shot film.

Having said that, if you are printing 8x10 images, I would say anything over 8 megapixels is actually going to look fine. So you could be ok cropping to 85 or even 100mm. And if you are printing 4x6 then you are probably fine even with the 4MP image! Also, if you are just looking at a picture on a cell phone or small old laptop, you might be fine cropping to 200mm and still seeing a nice image. But if you have a 4K monitor the 4MP image will not look great.

The problem is, you are probably better off with a small $100 dollar point and shoot that goes to 300mm equivalent rather than having a DSLR and a big expensive lens like the Sigma 18-35, and cropping 82% of your picture off.

It's just mathematics...

EDIT: The 200mm crop would actually be around 0.7 megapixels, so fine only for cell phone viewing.

I don't know why you would say its only for cell phone after cropping This is the photo of the 35mm after I cropped it to the same fov as the 200mm . I can see a difference but its not that big of a difference . I was standing in the same place with the camera on a tripod and all I did was change the lens . I took the photo into lightroom and cropped it so it looked the same length and width of the 200mm photo . That's all I did. I didn't change any of the settings on the right side of lightroom I just cropped it . Are you saying if I printed both off of flikr to a 4x6 print that I would see a big difference in the two ? . _IMG6181 | myridevlx600 | Flickr

[pentaxk3user]

It is the width and height of images in pixels. Try to zoom in both of them and you will see the difference in quality.

taktoon. I'm not understanding whats going on when I crop . The 2 photos of the house look like the same size to me on flickr . if the numbers are different would't the sizes of the photos be different on flickr ? Did I do something wrong to make them the same size on flickr going by 1026x670 and 6016x4000 ?

[Sandy Hancock]

Take a negative from a 8x10 plate camera, and make a contact print.
Now take a negative from a 110 film camera, and enlarge it to 8x10.

Which will be the better image?

Same principle.

[BrianR]

I don't know why you would say its only for cell phone after cropping This is the photo of the 35mm after I cropped it to the same fov as the 200mm . I can see a difference but its not that big of a difference . I was standing in the same place with the camera on a tripod and all I did was change the lens . I took the photo into lightroom and cropped it so it looked the same length and width of the 200mm photo . That's all I did. I didn't change any of the settings on the right side of lightroom I just cropped it . Are you saying if I printed both off of flikr to a 4x6 print that I would see a big difference in the two ? . _IMG6181 | myridevlx600 | Flickr

What were your export settings out of Lightroom?

Both your flickr examples are 4200x2813 so it looks like you upscaled the cropped image - this involves the computer making intelligent guesses on what the missing pixels should be. If you flip back and forth between them, the image that was cropped has way less detail. Upscaling algorithms are pretty good but they can't create detail that was never there. You don't have to look very close to see the difference in an extreme case like this.

It might be worth sending your two files off to be printed at 4x6" and also at 8x12" and doing a side-by-side comparison.

[pentaxk3user]

What were your export settings out of Lightroom?

Both your flickr examples are 4200x2813 so it looks like you upscaled the cropped image - this involves the computer making intelligent guesses on what the missing pixels should be. If you flip back and forth between them, the image that was cropped has way less detail. Upscaling algorithms are pretty good but they can't create detail that was never there. You don't have to look very close to see the difference in an extreme case like this.

It might be worth sending your two files off to be printed at 4x6" and also at 8x12" and doing a side-by-side comparison.

BrianR I don't know what I did the first time to make then the same size . I'm going to do it again and export them again . I must have had the image size checked with a size . This last time to get the 1026x670 and 6016x4000 numbers I unchecks the image size and got the 1026x670 and 6016x4000 numbers and a big difference in the mb sizes .I'll delete the 2 photos I have there now and replace them with the new numbers and see what it looks like of flickr . I haven't figured out what export setting to use yet . If I post a photo on facebook I will make the image sizing 8x8 or 10x10 because it fills up the space on facebook . I don't know what I'm doing or why yet . Here are the new sizes https://flic.kr/p/2hE4c4t https://flic.kr/p/2hE4c3w one should be 1026x670 and the other 6016x4000 If its not I don't know why . I didn't resize anything . will you look at both and tell me if I did it right . I noticed on the 35mm one it doesn't enlarge it as much as the 200mm photo .

[mikesbike]

I don't know why expensive longer FL lenses are made, or people bother to pay for them and lug them around, if all one has to do is crop images made with a WA lens.