Question about Full vs Crop Sensor Cameras

[photoflyer]

I prefer a 105 mm lens to an 85 mm almost all the time, and I found that the 135 mL to 180 mm prime lenses were good,

Would you agree that this depends in part on the environment in which you are shooting? Some spaces may not be large enough to enable one to get far enough away from the subject to properly compose the image. I think this is why some actually think of the 70-200 2.8 as a decent portrait lens in some situations.

 

[Derrel]

The shooting environment is a huge part of it. For example in most living rooms with a full frame camera the 85 mm lens is OK for portraits. In most living rooms with a crop frame camera, an 85 mm lens is extremely tight. For example at 20 feet with a full frame camera and 85 mm lens, you get a picture that is 8.47 feet tall; with a crop frame camera you have to be about 35 feet away to get the same 8.47 foot tall picture area. So let's say you wish to do a bridal portrait of a standing couple and leave a little bit of room below the feet and a little bit above the head,an easily-achievable end result with a full frame camera and 85 mm lens, but extremely difficult in many houses with a crop frame camera and an 85 mm lens. Yes the 70 to 200 mm zoom lens is an extremely useful lens on the full frame camera, but on the crop frame camera The same lens is extremely difficult to use in many smaller rooms

 

[Ema]

Thanks for all the feedback. Learning a lot. A few more newbie questions:
a) Even the f/stop has to be multiplied by 1.5 crop factor right. So does it mean that the fastest I can go with a f1.8 lens on a crop sensor camera is f2.8? (1.8*1.5). Or does it mean that I can use f1.8 but the photo quality if equivalent to a f2.8 on a full frame camera. In other words, I don't get the shallow depth of field of f1.8 but will get of a f2.8?
b) The kit lenses with D7100 are DX 18-55mm (f3.5-5.6) & DX 55-300mm (f4.5-5.6). As I learned more about photography and watched youtube, I figured I need to upgrade to the next set of lenses. One to get one for wide angle and also faster lenses at the different focal lengths. I noticed different recommendations. Some buy individual prime lenses (35 f1.4, 55 and 85) and some recommend zoom lenses (like Sigma 18-35 f1.8 and Sigma 50-150 f1.8 etc).

This is a hobby for me. Most of my pics will be of friends/family, some street shots and occasional landscape or travel photography. I am not going into professional portraits, but having the skill will help score some brownie points with my wifey no doubt.

Thanks for being patient with the newbie questions. Just trying to make the right decision.

 

[480sparky]

Thanks for all the feedback. Learning a lot. A few more newbie questions:
a) Even the f/stop has to be multiplied by 1.5 crop factor right. .........

No.

F/1.8 is f/1.8 is f/1.8. Aperture has nothing to do with sensor size.

 

[petrochemist]

I recall reading an article years ago about a portrait photographer that didn't use anything shorter than 300mm.

On large format that would be quite typical.
IIRC 300mm is the 'normal' focal length for 10x8" and it's like a short telephoto on 5x4

 

[petrochemist]

I would disagree with the idea that a lens of 85 mm in length is "the best" for
Portrait work. I prefer a 105 mm lens to an 85 mm almost all the time, and I found that the 135 mL to 180 mm prime lenses were good, over the years there have been many zoom Lenses which are really good for portraiture. One Lens was the 50 to 135 mm F3.5 Nikon AIS, as well as many 70 to 200 mm zoom lenses or 80 to 200 mm Zoom lenses, as well as the 75 to 150 mm series E zoom lens. The idea that the 85 mm lens is "the best" is really quite an oversimplification and is in my opinion and out right untruth.

I think it comes down to working space.
An 85mm won't fit a head & shoulders subject in at distances short enough where perspective is a significant issue. Yet doesn't need excessive distance. If space allows longer focal lengths will work well.
Shorter focal lengths can also work well IF the photographer is shooting full length portraits or people in their environment.

Of course the particular subject can have a significant effect on the best choice. Someone with very flat features might look better from somewhat closer, while someone with an unusually big nose benefits from the photographer using a longer lens

 

[petrochemist]

Thanks for all the feedback. Learning a lot. A few more newbie questions:
a) Even the f/stop has to be multiplied by 1.5 crop factor right. .........

No.

F/1.8 is f/1.8 is f/1.8. Aperture has nothing to do with sensor size.

Using the crop factor on aperture will give about the right values for DOF, (but I rarely bother calculating that anyway) for exposure purposes it's definitely not used.

 

[480sparky]

I recall reading an article years ago about a portrait photographer that didn't use anything shorter than 300mm.

On large format that would be quite typical.
IIRC 300mm is the 'normal' focal length for 10x8" and it's like a short telephoto on 5x4

Since the thread is about FX v. DX, that's a moot point.

 

[Designer]

..I figured I need to upgrade to the next set of lenses. I noticed different recommendations.

Yes, you will get different recommendations, depending on who you ask. Since you asked me, I will recommend some prime lenses.

Reason: With some research, you can get lenses that will help produce very good image quality while gaining aperture and that may cost less than a comparable zoom lens.

The reason why some people prefer zooms: Zoom lenses let you crop in camera, while prime lenses force you to walk closer or back up to frame your shot. Note: you can also just shoot "wide" and crop later on your computer.

Given the preferred subject material, for your first prime lens, get either a 50mm f/1.8 or 35mm f/1.8. These are good first primes and will give good results in "street", casual portraiture, landscape, and travel. And they are not expensive.

 

[Soocom1]

Thanks for all the feedback. Learning a lot. A few more newbie questions:
a) Even the f/stop has to be multiplied by 1.5 crop factor right. .........

No.

F/1.8 is f/1.8 is f/1.8. Aperture has nothing to do with sensor size.

This...
Plus, the aperture size number is based on DISTANCE from the FP to the Focal AREA. (The film or sensor).
so the numbers are the same because the MOUNTING distance is the same on a FF v Crop.

But I digress.

 

[Derrel]

Nikon has a couple of extremely sharp 85 mm G series lenses. The F 1.8 model and the F1.4 model are both two of the sharpest lenses Nikon makes priced under $4000. For many years I had the 85 mm F1.8 G but I recently sold it.

Most 85 mm lenses are designed in such a way that they typically have prettier bokehthan 50 mm lenses. The new 58 mm F1.4 is designed for very beautiful pictures. Some new 50 mm lenses from Zeiss and Sigma were designedfor critical sharpness, and have extremely hard bokeh.

 

[Derrel]

No, for exposure there is no need for any multiplication or factor ---F5.6 is the same amount of light on both full frame and crop frame. Possibly what you were reading about is called equivalence, which means that a small sensor requires a wider f-stop to give you the depth of field as the same lens when it is used on a larger sensor.

 

[Soocom1]

No, for exposure there is no need for any multiplication or factor ---F5.6 is the same amount of light on both full frame and crop frame. Possibly what you were reading about is called equivalence, which means that a small sensor requires a wider f-stop to give you the depth of field as the same lens when it is used on a larger sensor.

Good point.
The small ICA of an APS sensor would thus cut out the bokhe of a FF lens, rendering the intent moot.

 

[Derrel]

As far as equivalence, The people who seem to be most concerned with this do not shoot a APS-Csensors, but rather the small micro 4/3 size sensors.

In recent years there have been some very high speed primes made for people who would like to get really shallow depth of field, but who find that difficult to achieve with slow aperture lenses. Recently very high speed lenses such as F1.2 have been released by a number of companies.

The website cameraquest.com has quite a few write-upson these lenses

 

[Soocom1]

A couple of points.
1: A "crop" sensor is not really "cropped" but just smaller than the host lens intent.
The camera bodies are basically the same just diff. sized sensors. The mounting distance back of lens to ICA is the same for both. Just that an APS camera can allow back focusing.

2: The ICA because it is smaller on an APS, the actual image from a FF lens is exactly the same but covers less of the image circle.

Hence "cropped"

This cuts vingetting and barrel distortion when usinf FF lenses.

The same principle is applied when using a Med. Format lens on a 35mm. And even more so with an APS.